1 | // |
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2 | // Cforall Version 1.0.0 Copyright (C) 2020 University of Waterloo |
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3 | // |
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4 | // The contents of this file are covered under the licence agreement in the |
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5 | // file "LICENCE" distributed with Cforall. |
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6 | // |
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7 | // io.cfa -- |
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8 | // |
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9 | // Author : Thierry Delisle |
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10 | // Created On : Thu Apr 23 17:31:00 2020 |
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11 | // Last Modified By : |
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12 | // Last Modified On : |
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13 | // Update Count : |
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14 | // |
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15 | |
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16 | #define __cforall_thread__ |
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17 | |
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18 | #if defined(__CFA_DEBUG__) |
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19 | // #define __CFA_DEBUG_PRINT_IO__ |
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20 | // #define __CFA_DEBUG_PRINT_IO_CORE__ |
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21 | #endif |
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22 | |
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23 | |
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24 | #if defined(CFA_HAVE_LINUX_IO_URING_H) |
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25 | #define _GNU_SOURCE /* See feature_test_macros(7) */ |
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26 | #include <errno.h> |
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27 | #include <signal.h> |
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28 | #include <stdint.h> |
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29 | #include <string.h> |
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30 | #include <unistd.h> |
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31 | |
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32 | extern "C" { |
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33 | #include <sys/epoll.h> |
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34 | #include <sys/syscall.h> |
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35 | |
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36 | #include <linux/io_uring.h> |
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37 | } |
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38 | |
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39 | #include "stats.hfa" |
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40 | #include "kernel.hfa" |
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41 | #include "kernel/fwd.hfa" |
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42 | #include "io/types.hfa" |
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43 | |
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44 | // returns true of acquired as leader or second leader |
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45 | static inline bool try_lock( __leaderlock_t & this ) { |
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46 | const uintptr_t thrd = 1z | (uintptr_t)active_thread(); |
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47 | bool block; |
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48 | disable_interrupts(); |
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49 | for() { |
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50 | struct $thread * expected = this.value; |
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51 | if( 1p != expected && 0p != expected ) { |
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52 | /* paranoid */ verify( thrd != (uintptr_t)expected ); // We better not already be the next leader |
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53 | enable_interrupts( __cfaabi_dbg_ctx ); |
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54 | return false; |
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55 | } |
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56 | struct $thread * desired; |
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57 | if( 0p == expected ) { |
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58 | // If the lock isn't locked acquire it, no need to block |
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59 | desired = 1p; |
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60 | block = false; |
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61 | } |
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62 | else { |
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63 | // If the lock is already locked try becomming the next leader |
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64 | desired = (struct $thread *)thrd; |
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65 | block = true; |
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66 | } |
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67 | if( __atomic_compare_exchange_n(&this.value, &expected, desired, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST) ) break; |
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68 | } |
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69 | if( block ) { |
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70 | enable_interrupts( __cfaabi_dbg_ctx ); |
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71 | park( __cfaabi_dbg_ctx ); |
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72 | disable_interrupts(); |
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73 | } |
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74 | return true; |
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75 | } |
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76 | |
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77 | static inline bool next( __leaderlock_t & this ) { |
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78 | /* paranoid */ verify( ! kernelTLS.preemption_state.enabled ); |
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79 | struct $thread * nextt; |
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80 | for() { |
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81 | struct $thread * expected = this.value; |
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82 | /* paranoid */ verify( (1 & (uintptr_t)expected) == 1 ); // The lock better be locked |
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83 | |
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84 | struct $thread * desired; |
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85 | if( 1p == expected ) { |
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86 | // No next leader, just unlock |
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87 | desired = 0p; |
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88 | nextt = 0p; |
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89 | } |
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90 | else { |
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91 | // There is a next leader, remove but keep locked |
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92 | desired = 1p; |
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93 | nextt = (struct $thread *)(~1z & (uintptr_t)expected); |
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94 | } |
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95 | if( __atomic_compare_exchange_n(&this.value, &expected, desired, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST) ) break; |
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96 | } |
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97 | |
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98 | if(nextt) { |
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99 | unpark( nextt __cfaabi_dbg_ctx2 ); |
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100 | enable_interrupts( __cfaabi_dbg_ctx ); |
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101 | return true; |
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102 | } |
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103 | enable_interrupts( __cfaabi_dbg_ctx ); |
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104 | return false; |
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105 | } |
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106 | |
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107 | //============================================================================================= |
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108 | // I/O Syscall |
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109 | //============================================================================================= |
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110 | static int __io_uring_enter( struct __io_data & ring, unsigned to_submit, bool get ) { |
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111 | bool need_sys_to_submit = false; |
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112 | bool need_sys_to_complete = false; |
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113 | unsigned flags = 0; |
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114 | |
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115 | TO_SUBMIT: |
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116 | if( to_submit > 0 ) { |
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117 | if( !(ring.ring_flags & IORING_SETUP_SQPOLL) ) { |
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118 | need_sys_to_submit = true; |
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119 | break TO_SUBMIT; |
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120 | } |
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121 | if( (*ring.submit_q.flags) & IORING_SQ_NEED_WAKEUP ) { |
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122 | need_sys_to_submit = true; |
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123 | flags |= IORING_ENTER_SQ_WAKEUP; |
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124 | } |
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125 | } |
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126 | |
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127 | if( get && !(ring.ring_flags & IORING_SETUP_SQPOLL) ) { |
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128 | flags |= IORING_ENTER_GETEVENTS; |
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129 | if( (ring.ring_flags & IORING_SETUP_IOPOLL) ) { |
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130 | need_sys_to_complete = true; |
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131 | } |
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132 | } |
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133 | |
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134 | int ret = 0; |
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135 | if( need_sys_to_submit || need_sys_to_complete ) { |
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136 | ret = syscall( __NR_io_uring_enter, ring.fd, to_submit, 0, flags, 0p, _NSIG / 8); |
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137 | if( ret < 0 ) { |
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138 | switch((int)errno) { |
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139 | case EAGAIN: |
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140 | case EINTR: |
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141 | ret = -1; |
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142 | break; |
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143 | default: |
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144 | abort( "KERNEL ERROR: IO_URING SYSCALL - (%d) %s\n", (int)errno, strerror(errno) ); |
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145 | } |
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146 | } |
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147 | } |
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148 | |
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149 | // Memory barrier |
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150 | __atomic_thread_fence( __ATOMIC_SEQ_CST ); |
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151 | return ret; |
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152 | } |
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153 | |
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154 | //============================================================================================= |
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155 | // I/O Polling |
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156 | //============================================================================================= |
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157 | static unsigned __collect_submitions( struct __io_data & ring ); |
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158 | static __u32 __release_consumed_submission( struct __io_data & ring ); |
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159 | |
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160 | static inline void process(struct io_uring_cqe & cqe ) { |
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161 | struct __io_user_data_t * data = (struct __io_user_data_t *)(uintptr_t)cqe.user_data; |
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162 | __cfadbg_print_safe( io, "Kernel I/O : Syscall completed : cqe %p, result %d for %p\n", data, cqe.res, data->thrd ); |
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163 | |
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164 | data->result = cqe.res; |
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165 | post( data->sem ); |
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166 | } |
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167 | |
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168 | // Process a single completion message from the io_uring |
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169 | // This is NOT thread-safe |
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170 | static [int, bool] __drain_io( & struct __io_data ring ) { |
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171 | /* paranoid */ verify( !kernelTLS.preemption_state.enabled ); |
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172 | |
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173 | unsigned to_submit = 0; |
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174 | if( ring.poller_submits ) { |
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175 | // If the poller thread also submits, then we need to aggregate the submissions which are ready |
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176 | to_submit = __collect_submitions( ring ); |
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177 | } |
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178 | |
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179 | int ret = __io_uring_enter(ring, to_submit, true); |
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180 | if( ret < 0 ) { |
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181 | return [0, true]; |
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182 | } |
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183 | |
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184 | // update statistics |
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185 | if (to_submit > 0) { |
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186 | __STATS__( true, |
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187 | if( to_submit > 0 ) { |
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188 | io.submit_q.submit_avg.rdy += to_submit; |
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189 | io.submit_q.submit_avg.csm += ret; |
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190 | io.submit_q.submit_avg.cnt += 1; |
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191 | } |
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192 | ) |
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193 | } |
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194 | |
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195 | // Release the consumed SQEs |
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196 | __release_consumed_submission( ring ); |
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197 | |
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198 | // Drain the queue |
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199 | unsigned head = *ring.completion_q.head; |
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200 | unsigned tail = *ring.completion_q.tail; |
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201 | const __u32 mask = *ring.completion_q.mask; |
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202 | |
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203 | // Nothing was new return 0 |
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204 | if (head == tail) { |
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205 | return [0, to_submit > 0]; |
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206 | } |
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207 | |
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208 | __u32 count = tail - head; |
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209 | /* paranoid */ verify( count != 0 ); |
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210 | for(i; count) { |
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211 | unsigned idx = (head + i) & mask; |
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212 | struct io_uring_cqe & cqe = ring.completion_q.cqes[idx]; |
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213 | |
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214 | /* paranoid */ verify(&cqe); |
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215 | |
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216 | process( cqe ); |
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217 | } |
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218 | |
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219 | // Mark to the kernel that the cqe has been seen |
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220 | // Ensure that the kernel only sees the new value of the head index after the CQEs have been read. |
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221 | __atomic_thread_fence( __ATOMIC_SEQ_CST ); |
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222 | __atomic_fetch_add( ring.completion_q.head, count, __ATOMIC_RELAXED ); |
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223 | |
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224 | return [count, count > 0 || to_submit > 0]; |
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225 | } |
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226 | |
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227 | void main( $io_ctx_thread & this ) { |
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228 | epoll_event ev; |
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229 | __ioctx_register( this, ev ); |
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230 | |
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231 | __cfadbg_print_safe(io_core, "Kernel I/O : IO poller %p for ring %p ready\n", &this, &this.ring); |
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232 | |
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233 | int reset = 0; |
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234 | // Then loop until we need to start |
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235 | while(!__atomic_load_n(&this.done, __ATOMIC_SEQ_CST)) { |
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236 | // Drain the io |
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237 | int count; |
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238 | bool again; |
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239 | disable_interrupts(); |
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240 | [count, again] = __drain_io( *this.ring ); |
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241 | |
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242 | if(!again) reset++; |
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243 | |
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244 | // Update statistics |
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245 | __STATS__( true, |
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246 | io.complete_q.completed_avg.val += count; |
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247 | io.complete_q.completed_avg.cnt += 1; |
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248 | ) |
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249 | enable_interrupts( __cfaabi_dbg_ctx ); |
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250 | |
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251 | // If we got something, just yield and check again |
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252 | if(reset < 5) { |
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253 | yield(); |
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254 | } |
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255 | // We didn't get anything baton pass to the slow poller |
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256 | else { |
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257 | __STATS__( true, |
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258 | io.complete_q.blocks += 1; |
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259 | ) |
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260 | __cfadbg_print_safe(io_core, "Kernel I/O : Parking io poller %p\n", &this.self); |
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261 | reset = 0; |
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262 | |
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263 | // block this thread |
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264 | __ioctx_prepare_block( this, ev ); |
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265 | wait( this.sem ); |
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266 | } |
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267 | } |
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268 | |
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269 | __cfadbg_print_safe(io_core, "Kernel I/O : Fast poller for ring %p stopping\n", &this.ring); |
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270 | } |
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271 | |
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272 | //============================================================================================= |
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273 | // I/O Submissions |
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274 | //============================================================================================= |
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275 | |
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276 | // Submition steps : |
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277 | // 1 - Allocate a queue entry. The ring already has memory for all entries but only the ones |
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278 | // listed in sq.array are visible by the kernel. For those not listed, the kernel does not |
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279 | // offer any assurance that an entry is not being filled by multiple flags. Therefore, we |
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280 | // need to write an allocator that allows allocating concurrently. |
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281 | // |
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282 | // 2 - Actually fill the submit entry, this is the only simple and straightforward step. |
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283 | // |
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284 | // 3 - Append the entry index to the array and adjust the tail accordingly. This operation |
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285 | // needs to arrive to two concensus at the same time: |
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286 | // A - The order in which entries are listed in the array: no two threads must pick the |
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287 | // same index for their entries |
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288 | // B - When can the tail be update for the kernel. EVERY entries in the array between |
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289 | // head and tail must be fully filled and shouldn't ever be touched again. |
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290 | // |
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291 | |
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292 | [* struct io_uring_sqe, __u32] __submit_alloc( struct __io_data & ring, __u64 data ) { |
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293 | /* paranoid */ verify( data != 0 ); |
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294 | |
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295 | // Prepare the data we need |
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296 | __attribute((unused)) int len = 0; |
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297 | __attribute((unused)) int block = 0; |
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298 | __u32 cnt = *ring.submit_q.num; |
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299 | __u32 mask = *ring.submit_q.mask; |
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300 | |
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301 | disable_interrupts(); |
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302 | __u32 off = __tls_rand(); |
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303 | enable_interrupts( __cfaabi_dbg_ctx ); |
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304 | |
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305 | // Loop around looking for an available spot |
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306 | for() { |
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307 | // Look through the list starting at some offset |
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308 | for(i; cnt) { |
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309 | __u64 expected = 0; |
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310 | __u32 idx = (i + off) & mask; |
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311 | struct io_uring_sqe * sqe = &ring.submit_q.sqes[idx]; |
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312 | volatile __u64 * udata = &sqe->user_data; |
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313 | |
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314 | if( *udata == expected && |
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315 | __atomic_compare_exchange_n( udata, &expected, data, true, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED ) ) |
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316 | { |
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317 | // update statistics |
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318 | __STATS__( false, |
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319 | io.submit_q.alloc_avg.val += len; |
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320 | io.submit_q.alloc_avg.block += block; |
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321 | io.submit_q.alloc_avg.cnt += 1; |
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322 | ) |
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323 | |
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324 | |
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325 | // Success return the data |
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326 | return [sqe, idx]; |
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327 | } |
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328 | verify(expected != data); |
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329 | |
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330 | len ++; |
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331 | } |
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332 | |
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333 | block++; |
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334 | yield(); |
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335 | } |
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336 | } |
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337 | |
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338 | static inline __u32 __submit_to_ready_array( struct __io_data & ring, __u32 idx, const __u32 mask ) { |
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339 | /* paranoid */ verify( idx <= mask ); |
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340 | /* paranoid */ verify( idx != -1ul32 ); |
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341 | |
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342 | // We need to find a spot in the ready array |
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343 | __attribute((unused)) int len = 0; |
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344 | __attribute((unused)) int block = 0; |
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345 | __u32 ready_mask = ring.submit_q.ready_cnt - 1; |
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346 | |
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347 | disable_interrupts(); |
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348 | __u32 off = __tls_rand(); |
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349 | enable_interrupts( __cfaabi_dbg_ctx ); |
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350 | |
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351 | __u32 picked; |
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352 | LOOKING: for() { |
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353 | for(i; ring.submit_q.ready_cnt) { |
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354 | picked = (i + off) & ready_mask; |
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355 | __u32 expected = -1ul32; |
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356 | if( __atomic_compare_exchange_n( &ring.submit_q.ready[picked], &expected, idx, true, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED ) ) { |
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357 | break LOOKING; |
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358 | } |
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359 | verify(expected != idx); |
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360 | |
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361 | len ++; |
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362 | } |
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363 | |
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364 | block++; |
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365 | |
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366 | __u32 released = __release_consumed_submission( ring ); |
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367 | if( released == 0 ) { |
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368 | yield(); |
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369 | } |
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370 | } |
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371 | |
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372 | // update statistics |
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373 | __STATS__( false, |
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374 | io.submit_q.look_avg.val += len; |
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375 | io.submit_q.look_avg.block += block; |
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376 | io.submit_q.look_avg.cnt += 1; |
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377 | ) |
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378 | |
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379 | return picked; |
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380 | } |
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381 | |
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382 | void __submit( struct io_context * ctx, __u32 idx ) __attribute__((nonnull (1))) { |
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383 | __io_data & ring = *ctx->thrd.ring; |
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384 | // Get now the data we definetely need |
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385 | volatile __u32 * const tail = ring.submit_q.tail; |
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386 | const __u32 mask = *ring.submit_q.mask; |
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387 | |
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388 | // There are 2 submission schemes, check which one we are using |
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389 | if( ring.poller_submits ) { |
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390 | // If the poller thread submits, then we just need to add this to the ready array |
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391 | __submit_to_ready_array( ring, idx, mask ); |
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392 | |
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393 | post( ctx->thrd.sem ); |
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394 | |
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395 | __cfadbg_print_safe( io, "Kernel I/O : Added %u to ready for %p\n", idx, active_thread() ); |
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396 | } |
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397 | else if( ring.eager_submits ) { |
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398 | __u32 picked = __submit_to_ready_array( ring, idx, mask ); |
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399 | |
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400 | #if defined(LEADER_LOCK) |
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401 | if( !try_lock(ring.submit_q.submit_lock) ) { |
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402 | __STATS__( false, |
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403 | io.submit_q.helped += 1; |
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404 | ) |
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405 | return; |
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406 | } |
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407 | /* paranoid */ verify( ! kernelTLS.preemption_state.enabled ); |
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408 | __STATS__( true, |
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409 | io.submit_q.leader += 1; |
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410 | ) |
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411 | #else |
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412 | for() { |
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413 | yield(); |
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414 | |
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415 | if( try_lock(ring.submit_q.submit_lock __cfaabi_dbg_ctx2) ) { |
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416 | __STATS__( false, |
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417 | io.submit_q.leader += 1; |
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418 | ) |
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419 | break; |
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420 | } |
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421 | |
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422 | // If some one else collected our index, we are done |
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423 | #warning ABA problem |
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424 | if( ring.submit_q.ready[picked] != idx ) { |
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425 | __STATS__( false, |
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426 | io.submit_q.helped += 1; |
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427 | ) |
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428 | return; |
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429 | } |
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430 | |
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431 | __STATS__( false, |
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432 | io.submit_q.busy += 1; |
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433 | ) |
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434 | } |
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435 | #endif |
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436 | |
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437 | // We got the lock |
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438 | // Collect the submissions |
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439 | unsigned to_submit = __collect_submitions( ring ); |
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440 | |
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441 | // Actually submit |
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442 | int ret = __io_uring_enter( ring, to_submit, false ); |
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443 | |
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444 | #if defined(LEADER_LOCK) |
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445 | /* paranoid */ verify( ! kernelTLS.preemption_state.enabled ); |
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446 | next(ring.submit_q.submit_lock); |
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447 | #else |
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448 | unlock(ring.submit_q.submit_lock); |
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449 | #endif |
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450 | if( ret < 0 ) return; |
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451 | |
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452 | // Release the consumed SQEs |
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453 | __release_consumed_submission( ring ); |
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454 | |
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455 | // update statistics |
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456 | __STATS__( false, |
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457 | io.submit_q.submit_avg.rdy += to_submit; |
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458 | io.submit_q.submit_avg.csm += ret; |
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459 | io.submit_q.submit_avg.cnt += 1; |
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460 | ) |
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461 | } |
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462 | else { |
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463 | // get mutual exclusion |
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464 | #if defined(LEADER_LOCK) |
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465 | while(!try_lock(ring.submit_q.submit_lock)); |
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466 | #else |
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467 | lock(ring.submit_q.submit_lock __cfaabi_dbg_ctx2); |
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468 | #endif |
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469 | |
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470 | /* paranoid */ verifyf( ring.submit_q.sqes[ idx ].user_data != 0, |
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471 | /* paranoid */ "index %u already reclaimed\n" |
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472 | /* paranoid */ "head %u, prev %u, tail %u\n" |
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473 | /* paranoid */ "[-0: %u,-1: %u,-2: %u,-3: %u]\n", |
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474 | /* paranoid */ idx, |
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475 | /* paranoid */ *ring.submit_q.head, ring.submit_q.prev_head, *tail |
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476 | /* paranoid */ ,ring.submit_q.array[ ((*ring.submit_q.head) - 0) & (*ring.submit_q.mask) ] |
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477 | /* paranoid */ ,ring.submit_q.array[ ((*ring.submit_q.head) - 1) & (*ring.submit_q.mask) ] |
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478 | /* paranoid */ ,ring.submit_q.array[ ((*ring.submit_q.head) - 2) & (*ring.submit_q.mask) ] |
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479 | /* paranoid */ ,ring.submit_q.array[ ((*ring.submit_q.head) - 3) & (*ring.submit_q.mask) ] |
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480 | /* paranoid */ ); |
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481 | |
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482 | // Append to the list of ready entries |
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483 | |
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484 | /* paranoid */ verify( idx <= mask ); |
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485 | ring.submit_q.array[ (*tail) & mask ] = idx; |
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486 | __atomic_fetch_add(tail, 1ul32, __ATOMIC_SEQ_CST); |
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487 | |
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488 | // Submit however, many entries need to be submitted |
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489 | int ret = __io_uring_enter( ring, 1, false ); |
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490 | if( ret < 0 ) { |
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491 | switch((int)errno) { |
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492 | default: |
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493 | abort( "KERNEL ERROR: IO_URING SUBMIT - %s\n", strerror(errno) ); |
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494 | } |
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495 | } |
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496 | |
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497 | // update statistics |
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498 | __STATS__( false, |
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499 | io.submit_q.submit_avg.csm += 1; |
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500 | io.submit_q.submit_avg.cnt += 1; |
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501 | ) |
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502 | |
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503 | // Release the consumed SQEs |
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504 | __release_consumed_submission( ring ); |
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505 | |
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506 | #if defined(LEADER_LOCK) |
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507 | next(ring.submit_q.submit_lock); |
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508 | #else |
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509 | unlock(ring.submit_q.submit_lock); |
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510 | #endif |
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511 | |
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512 | __cfadbg_print_safe( io, "Kernel I/O : Performed io_submit for %p, returned %d\n", active_thread(), ret ); |
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513 | } |
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514 | } |
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515 | |
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516 | #define PARTIAL_SUBMIT 32 |
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517 | static unsigned __collect_submitions( struct __io_data & ring ) { |
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518 | /* paranoid */ verify( ring.submit_q.ready != 0p ); |
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519 | /* paranoid */ verify( ring.submit_q.ready_cnt > 0 ); |
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520 | |
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521 | unsigned to_submit = 0; |
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522 | __u32 tail = *ring.submit_q.tail; |
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523 | const __u32 mask = *ring.submit_q.mask; |
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524 | #if defined(PARTIAL_SUBMIT) |
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525 | #if defined(LEADER_LOCK) |
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526 | #error PARTIAL_SUBMIT and LEADER_LOCK cannot co-exist |
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527 | #endif |
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528 | const __u32 cnt = ring.submit_q.ready_cnt > PARTIAL_SUBMIT ? PARTIAL_SUBMIT : ring.submit_q.ready_cnt; |
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529 | const __u32 offset = ring.submit_q.prev_ready; |
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530 | ring.submit_q.prev_ready += cnt; |
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531 | #else |
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532 | const __u32 cnt = ring.submit_q.ready_cnt; |
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533 | const __u32 offset = 0; |
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534 | #endif |
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535 | |
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536 | // Go through the list of ready submissions |
---|
537 | for( c; cnt ) { |
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538 | __u32 i = (offset + c) % ring.submit_q.ready_cnt; |
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539 | |
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540 | // replace any submission with the sentinel, to consume it. |
---|
541 | __u32 idx = __atomic_exchange_n( &ring.submit_q.ready[i], -1ul32, __ATOMIC_RELAXED); |
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542 | |
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543 | // If it was already the sentinel, then we are done |
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544 | if( idx == -1ul32 ) continue; |
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545 | |
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546 | // If we got a real submission, append it to the list |
---|
547 | ring.submit_q.array[ (tail + to_submit) & mask ] = idx & mask; |
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548 | to_submit++; |
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549 | } |
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550 | |
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551 | // Increment the tail based on how many we are ready to submit |
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552 | __atomic_fetch_add(ring.submit_q.tail, to_submit, __ATOMIC_SEQ_CST); |
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553 | |
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554 | return to_submit; |
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555 | } |
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556 | |
---|
557 | static __u32 __release_consumed_submission( struct __io_data & ring ) { |
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558 | const __u32 smask = *ring.submit_q.mask; |
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559 | |
---|
560 | if( !try_lock(ring.submit_q.release_lock __cfaabi_dbg_ctx2) ) return 0; |
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561 | __u32 chead = *ring.submit_q.head; |
---|
562 | __u32 phead = ring.submit_q.prev_head; |
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563 | ring.submit_q.prev_head = chead; |
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564 | unlock(ring.submit_q.release_lock); |
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565 | |
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566 | __u32 count = chead - phead; |
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567 | for( i; count ) { |
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568 | __u32 idx = ring.submit_q.array[ (phead + i) & smask ]; |
---|
569 | ring.submit_q.sqes[ idx ].user_data = 0; |
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570 | } |
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571 | return count; |
---|
572 | } |
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573 | #endif |
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