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io.cfa@ e82a6e4f

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ADT ast-experimental pthread-emulation qualifiedEnum

Last change on this file since e82a6e4f was bdfd0bd, checked in by Thierry Delisle <tdelisle@…>, 4 years ago
EINTR will no longer wakeup the idle_sleep.
Property mode set to `100644`
File size: 21.3 KB

Rev	Line
[ecf6b46]	1	//
	2	// Cforall Version 1.0.0 Copyright (C) 2020 University of Waterloo
	3	//
	4	// The contents of this file are covered under the licence agreement in the
	5	// file "LICENCE" distributed with Cforall.
	6	//
	7	// io.cfa --
	8	//
	9	// Author : Thierry Delisle
	10	// Created On : Thu Apr 23 17:31:00 2020
	11	// Last Modified By :
	12	// Last Modified On :
	13	// Update Count :
	14	//
	15
[3e2b9c9]	16	#define __cforall_thread__
[43784ac]	17	#define _GNU_SOURCE
[3e2b9c9]	18
[20ab637]	19	#if defined(__CFA_DEBUG__)
[d60d30e]	20	// #define __CFA_DEBUG_PRINT_IO__
	21	// #define __CFA_DEBUG_PRINT_IO_CORE__
[20ab637]	22	#endif
[4069faad]	23
[f6660520]	24
[3e2b9c9]	25	#if defined(CFA_HAVE_LINUX_IO_URING_H)
[31bb2e1]	26	#include <errno.h>
[3e2b9c9]	27	#include <signal.h>
[31bb2e1]	28	#include <stdint.h>
	29	#include <string.h>
	30	#include <unistd.h>
	31
[92976d9]	32	extern "C" {
	33	#include <sys/syscall.h>
[dddb3dd0]	34	#include <sys/eventfd.h>
[d3605f8]	35	#include <sys/uio.h>
[92976d9]	36
	37	#include <linux/io_uring.h>
	38	}
	39
[3e2b9c9]	40	#include "stats.hfa"
	41	#include "kernel.hfa"
	42	#include "kernel/fwd.hfa"
[708ae38]	43	#include "kernel/private.hfa"
[78a580d]	44	#include "kernel/cluster.hfa"
[3e2b9c9]	45	#include "io/types.hfa"
[185efe6]	46
[2fab24e3]	47	__attribute__((unused)) static const char * opcodes[] = {
[426f60c]	48	"OP_NOP",
	49	"OP_READV",
	50	"OP_WRITEV",
	51	"OP_FSYNC",
	52	"OP_READ_FIXED",
	53	"OP_WRITE_FIXED",
	54	"OP_POLL_ADD",
	55	"OP_POLL_REMOVE",
	56	"OP_SYNC_FILE_RANGE",
	57	"OP_SENDMSG",
	58	"OP_RECVMSG",
	59	"OP_TIMEOUT",
	60	"OP_TIMEOUT_REMOVE",
	61	"OP_ACCEPT",
	62	"OP_ASYNC_CANCEL",
	63	"OP_LINK_TIMEOUT",
	64	"OP_CONNECT",
	65	"OP_FALLOCATE",
	66	"OP_OPENAT",
	67	"OP_CLOSE",
	68	"OP_FILES_UPDATE",
	69	"OP_STATX",
	70	"OP_READ",
	71	"OP_WRITE",
	72	"OP_FADVISE",
	73	"OP_MADVISE",
	74	"OP_SEND",
	75	"OP_RECV",
	76	"OP_OPENAT2",
	77	"OP_EPOLL_CTL",
	78	"OP_SPLICE",
	79	"OP_PROVIDE_BUFFERS",
	80	"OP_REMOVE_BUFFERS",
	81	"OP_TEE",
	82	"INVALID_OP"
	83	};
	84
[11054eb]	85	static $io_context * __ioarbiter_allocate( $io_arbiter & this, __u32 idxs[], __u32 want );
	86	static void __ioarbiter_submit( $io_context * , __u32 idxs[], __u32 have, bool lazy );
	87	static void __ioarbiter_flush ( $io_context & );
[dddb3dd0]	88	static inline void __ioarbiter_notify( $io_context & ctx );
[92976d9]	89	//=============================================================================================
	90	// I/O Polling
	91	//=============================================================================================
[78da4ab]	92	static inline unsigned __flush( struct $io_context & );
	93	static inline __u32 __release_sqes( struct $io_context & );
[24e321c]	94	extern void __kernel_unpark( thread$ * thrd, unpark_hint );
[1d5e4711]	95
[18f7858]	96	static void ioring_syscsll( struct $io_context & ctx, unsigned int min_comp, unsigned int flags ) {
	97	__STATS__( true, io.calls.flush++; )
[bdfd0bd]	98	int ret;
	99	for() {
	100	ret = syscall( __NR_io_uring_enter, ctx.fd, ctx.sq.to_submit, min_comp, flags, (sigset_t *)0p, _NSIG / 8);
	101	if( ret < 0 ) {
	102	switch((int)errno) {
	103	case EINTR:
	104	continue;
	105	case EAGAIN:
	106	case EBUSY:
	107	// Update statistics
	108	__STATS__( false, io.calls.errors.busy ++; )
	109	return false;
	110	default:
	111	abort( "KERNEL ERROR: IO_URING SYSCALL - (%d) %s\n", (int)errno, strerror(errno) );
	112	}
[18f7858]	113	}
[bdfd0bd]	114	break;
[18f7858]	115	}
	116
	117	__cfadbg_print_safe(io, "Kernel I/O : %u submitted to io_uring %d\n", ret, ctx.fd);
	118	__STATS__( true, io.calls.submitted += ret; )
	119	/* paranoid / verify( ctx.sq.to_submit <= ctx.sq.num );
	120	/* paranoid */ verify( ctx.sq.to_submit >= ret );
	121
	122	ctx.sq.to_submit -= ret;
	123
	124	/* paranoid / verify( ctx.sq.to_submit <= ctx.sq.num );
	125
	126	// Release the consumed SQEs
	127	__release_sqes( ctx );
	128
[dddb3dd0]	129	/* paranoid */ verify( ! __preemption_enabled() );
[6f121b8]	130
[18f7858]	131	__atomic_store_n(&ctx.proc->io.pending, false, __ATOMIC_RELAXED);
	132	}
	133
	134	static bool try_acquire( $io_context * ctx ) __attribute__((nonnull(1))) {
	135	/* paranoid */ verify( ! __preemption_enabled() );
	136	/* paranoid */ verify( ready_schedule_islocked() );
[92976d9]	137
[d60d30e]	138
[3caf5e3]	139	{
	140	const __u32 head = *ctx->cq.head;
	141	const __u32 tail = *ctx->cq.tail;
	142
	143	if(head == tail) return false;
	144	}
[c1c95b1]	145
[3caf5e3]	146	// Drain the queue
[4ecc35a]	147	if(!__atomic_try_acquire(&ctx->cq.lock)) {
[54c1196]	148	__STATS__( false, io.calls.locked++; )
[4ecc35a]	149	return false;
	150	}
	151
[18f7858]	152	return true;
	153	}
	154
	155	static bool __cfa_do_drain( $io_context * ctx, cluster * cltr ) __attribute__((nonnull(1, 2))) {
	156	/* paranoid */ verify( ! __preemption_enabled() );
	157	/* paranoid */ verify( ready_schedule_islocked() );
	158	/* paranoid */ verify( ctx->cq.lock == true );
	159
	160	const __u32 mask = *ctx->cq.mask;
[78a580d]	161	unsigned long long ts_prev = ctx->cq.ts;
	162
[3caf5e3]	163	// re-read the head and tail in case it already changed.
	164	const __u32 head = *ctx->cq.head;
	165	const __u32 tail = *ctx->cq.tail;
	166	const __u32 count = tail - head;
	167	__STATS__( false, io.calls.drain++; io.calls.completed += count; )
	168
[d384787]	169	for(i; count) {
[6f121b8]	170	unsigned idx = (head + i) & mask;
[dddb3dd0]	171	volatile struct io_uring_cqe & cqe = ctx->cq.cqes[idx];
[92976d9]	172
[d384787]	173	/* paranoid */ verify(&cqe);
[92976d9]	174
[78da4ab]	175	struct io_future_t * future = (struct io_future_t *)(uintptr_t)cqe.user_data;
[1e6ffb44]	176	// __cfadbg_print_safe( io, "Kernel I/O : Syscall completed : cqe %p, result %d for %p\n", &cqe, cqe.res, future );
[78da4ab]	177
[24e321c]	178	__kernel_unpark( fulfil( *future, cqe.res, false ), UNPARK_LOCAL );
[78da4ab]	179	}
	180
[78a580d]	181	unsigned long long ts_next = ctx->cq.ts = rdtscl();
[2d8f7b0]	182
[92976d9]	183	// Mark to the kernel that the cqe has been seen
	184	// Ensure that the kernel only sees the new value of the head index after the CQEs have been read.
[dddb3dd0]	185	__atomic_store_n( ctx->cq.head, head + count, __ATOMIC_SEQ_CST );
[d28b70a]	186	ctx->proc->idle_wctx.drain_time = ts_next;
[92976d9]	187
[1e6ffb44]	188	__cfadbg_print_safe(io, "Kernel I/O : %u completed age %llu\n", count, ts_next);
[e9c0b4c]	189	/* paranoid */ verify( ready_schedule_islocked() );
[dddb3dd0]	190	/* paranoid */ verify( ! __preemption_enabled() );
	191
[4ecc35a]	192	__atomic_unlock(&ctx->cq.lock);
	193
[78a580d]	194	touch_tsc( cltr->sched.io.tscs, ctx->cq.id, ts_prev, ts_next );
	195
[c1c95b1]	196	return true;
[92976d9]	197	}
	198
[4479890]	199	bool __cfa_io_drain( processor * proc ) {
	200	bool local = false;
	201	bool remote = false;
	202
[18f7858]	203	ready_schedule_lock();
	204
[4479890]	205	cluster * const cltr = proc->cltr;
	206	$io_context * const ctx = proc->io.ctx;
	207	/* paranoid */ verify( cltr );
	208	/* paranoid */ verify( ctx );
	209
	210	with(cltr->sched) {
	211	const size_t ctxs_count = io.count;
	212
	213	/* paranoid */ verify( ready_schedule_islocked() );
	214	/* paranoid */ verify( ! __preemption_enabled() );
	215	/* paranoid */ verify( active_processor() == proc );
	216	/* paranoid */ verify( __shard_factor.io > 0 );
	217	/* paranoid */ verify( ctxs_count > 0 );
	218	/* paranoid */ verify( ctx->cq.id < ctxs_count );
	219
	220	const unsigned this_cache = cache_id(cltr, ctx->cq.id / __shard_factor.io);
	221	const unsigned long long ctsc = rdtscl();
	222
	223	if(proc->io.target == MAX) {
	224	uint64_t chaos = __tls_rand();
	225	unsigned ext = chaos & 0xff;
	226	unsigned other = (chaos >> 8) % (ctxs_count);
	227
	228	if(ext < 3 \|\| __atomic_load_n(&caches[other / __shard_factor.io].id, __ATOMIC_RELAXED) == this_cache) {
	229	proc->io.target = other;
	230	}
	231	}
	232	else {
	233	const unsigned target = proc->io.target;
	234	/* paranoid */ verify( io.tscs[target].tv != MAX );
[18f7858]	235	HELP: if(target < ctxs_count) {
[4479890]	236	const unsigned long long cutoff = calc_cutoff(ctsc, ctx->cq.id, ctxs_count, io.data, io.tscs, __shard_factor.io);
	237	const unsigned long long age = moving_average(ctsc, io.tscs[target].tv, io.tscs[target].ma);
[edf247b]	238	__cfadbg_print_safe(io, "Kernel I/O: Help attempt on %u from %u, age %'llu vs cutoff %'llu, %s\n", target, ctx->cq.id, age, cutoff, age > cutoff ? "yes" : "no");
[18f7858]	239	if(age <= cutoff) break HELP;
	240
	241	if(!try_acquire(io.data[target])) break HELP;
	242
	243	if(!__cfa_do_drain( io.data[target], cltr )) break HELP;
	244
	245	remote = true;
	246	__STATS__( false, io.calls.helped++; )
[4479890]	247	}
	248	proc->io.target = MAX;
	249	}
	250	}
	251
	252
	253	// Drain the local queue
[18f7858]	254	if(try_acquire( proc->io.ctx )) {
	255	local = __cfa_do_drain( proc->io.ctx, cltr );
	256	}
[4479890]	257
	258	/* paranoid */ verify( ready_schedule_islocked() );
	259	/* paranoid */ verify( ! __preemption_enabled() );
	260	/* paranoid */ verify( active_processor() == proc );
[18f7858]	261
	262	ready_schedule_unlock();
[4479890]	263	return local \|\| remote;
	264	}
	265
[18f7858]	266	bool __cfa_io_flush( processor * proc ) {
[dddb3dd0]	267	/* paranoid */ verify( ! __preemption_enabled() );
	268	/* paranoid */ verify( proc );
	269	/* paranoid */ verify( proc->io.ctx );
[1539bbd]	270
[dddb3dd0]	271	$io_context & ctx = *proc->io.ctx;
[78da4ab]	272
[11054eb]	273	__ioarbiter_flush( ctx );
[3c039b0]	274
[18f7858]	275	if(ctx.sq.to_submit != 0) {
	276	ioring_syscsll(ctx, 0, 0);
[21a5bfb7]	277
	278	}
[61dd73d]	279
[18f7858]	280	return __cfa_io_drain( proc );
[61dd73d]	281	}
[f6660520]	282
[92976d9]	283	//=============================================================================================
	284	// I/O Submissions
	285	//=============================================================================================
	286
[2d8f7b0]	287	// Submition steps :
[e46c753]	288	// 1 - Allocate a queue entry. The ring already has memory for all entries but only the ones
[2d8f7b0]	289	// listed in sq.array are visible by the kernel. For those not listed, the kernel does not
	290	// offer any assurance that an entry is not being filled by multiple flags. Therefore, we
	291	// need to write an allocator that allows allocating concurrently.
	292	//
[e46c753]	293	// 2 - Actually fill the submit entry, this is the only simple and straightforward step.
[2d8f7b0]	294	//
[e46c753]	295	// 3 - Append the entry index to the array and adjust the tail accordingly. This operation
[2d8f7b0]	296	// needs to arrive to two concensus at the same time:
	297	// A - The order in which entries are listed in the array: no two threads must pick the
	298	// same index for their entries
	299	// B - When can the tail be update for the kernel. EVERY entries in the array between
	300	// head and tail must be fully filled and shouldn't ever be touched again.
	301	//
[78da4ab]	302	//=============================================================================================
	303	// Allocation
	304	// for user's convenience fill the sqes from the indexes
	305	static inline void __fill(struct io_uring_sqe * out_sqes[], __u32 want, __u32 idxs[], struct $io_context * ctx) {
	306	struct io_uring_sqe * sqes = ctx->sq.sqes;
	307	for(i; want) {
[1e6ffb44]	308	// __cfadbg_print_safe(io, "Kernel I/O : filling loop\n");
[78da4ab]	309	out_sqes[i] = &sqes[idxs[i]];
	310	}
	311	}
[2489d31]	312
[78da4ab]	313	// Try to directly allocate from the a given context
	314	// Not thread-safe
	315	static inline bool __alloc(struct $io_context * ctx, __u32 idxs[], __u32 want) {
	316	__sub_ring_t & sq = ctx->sq;
	317	const __u32 mask = *sq.mask;
	318	__u32 fhead = sq.free_ring.head; // get the current head of the queue
	319	__u32 ftail = sq.free_ring.tail; // get the current tail of the queue
[2489d31]	320
[78da4ab]	321	// If we don't have enough sqes, fail
	322	if((ftail - fhead) < want) { return false; }
[426f60c]	323
[78da4ab]	324	// copy all the indexes we want from the available list
	325	for(i; want) {
[1e6ffb44]	326	// __cfadbg_print_safe(io, "Kernel I/O : allocating loop\n");
[78da4ab]	327	idxs[i] = sq.free_ring.array[(fhead + i) & mask];
[6f121b8]	328	}
[2489d31]	329
[78da4ab]	330	// Advance the head to mark the indexes as consumed
	331	__atomic_store_n(&sq.free_ring.head, fhead + want, __ATOMIC_RELEASE);
[df40a56]	332
[78da4ab]	333	// return success
	334	return true;
	335	}
[df40a56]	336
[78da4ab]	337	// Allocate an submit queue entry.
	338	// The kernel cannot see these entries until they are submitted, but other threads must be
	339	// able to see which entries can be used and which are already un used by an other thread
	340	// for convenience, return both the index and the pointer to the sqe
	341	// sqe == &sqes[idx]
	342	struct $io_context * cfa_io_allocate(struct io_uring_sqe * sqes[], __u32 idxs[], __u32 want) {
[1e6ffb44]	343	// __cfadbg_print_safe(io, "Kernel I/O : attempting to allocate %u\n", want);
[df40a56]	344
[78da4ab]	345	disable_interrupts();
	346	processor * proc = __cfaabi_tls.this_processor;
[dddb3dd0]	347	$io_context * ctx = proc->io.ctx;
[78da4ab]	348	/* paranoid */ verify( __cfaabi_tls.this_processor );
[dddb3dd0]	349	/* paranoid */ verify( ctx );
[78da4ab]	350
[1e6ffb44]	351	// __cfadbg_print_safe(io, "Kernel I/O : attempting to fast allocation\n");
[78da4ab]	352
[dddb3dd0]	353	// We can proceed to the fast path
	354	if( __alloc(ctx, idxs, want) ) {
	355	// Allocation was successful
	356	__STATS__( true, io.alloc.fast += 1; )
[a3821fa]	357	enable_interrupts();
[df40a56]	358
[1e6ffb44]	359	// __cfadbg_print_safe(io, "Kernel I/O : fast allocation successful from ring %d\n", ctx->fd);
[2fafe7e]	360
[dddb3dd0]	361	__fill( sqes, want, idxs, ctx );
	362	return ctx;
[df40a56]	363	}
[dddb3dd0]	364	// The fast path failed, fallback
	365	__STATS__( true, io.alloc.fail += 1; )
[df40a56]	366
[78da4ab]	367	// Fast path failed, fallback on arbitration
[d60d30e]	368	__STATS__( true, io.alloc.slow += 1; )
[a3821fa]	369	enable_interrupts();
[78da4ab]	370
[dddb3dd0]	371	$io_arbiter * ioarb = proc->cltr->io.arbiter;
	372	/* paranoid */ verify( ioarb );
	373
[1e6ffb44]	374	// __cfadbg_print_safe(io, "Kernel I/O : falling back on arbiter for allocation\n");
[78da4ab]	375
[11054eb]	376	struct $io_context * ret = __ioarbiter_allocate(*ioarb, idxs, want);
[78da4ab]	377
[1e6ffb44]	378	// __cfadbg_print_safe(io, "Kernel I/O : slow allocation completed from ring %d\n", ret->fd);
[df40a56]	379
[78da4ab]	380	__fill( sqes, want, idxs,ret );
	381	return ret;
[df40a56]	382	}
	383
[78da4ab]	384	//=============================================================================================
	385	// submission
[2432e8e]	386	static inline void __submit_only( struct $io_context * ctx, __u32 idxs[], __u32 have) {
[78da4ab]	387	// We can proceed to the fast path
	388	// Get the right objects
	389	__sub_ring_t & sq = ctx->sq;
	390	const __u32 mask = *sq.mask;
[dddb3dd0]	391	__u32 tail = *sq.kring.tail;
[78da4ab]	392
	393	// Add the sqes to the array
	394	for( i; have ) {
[1e6ffb44]	395	// __cfadbg_print_safe(io, "Kernel I/O : __submit loop\n");
[78da4ab]	396	sq.kring.array[ (tail + i) & mask ] = idxs[i];
[426f60c]	397	}
	398
[78da4ab]	399	// Make the sqes visible to the submitter
[dddb3dd0]	400	__atomic_store_n(sq.kring.tail, tail + have, __ATOMIC_RELEASE);
[e8ac228]	401	sq.to_submit += have;
[426f60c]	402
[d529ad0]	403	__atomic_store_n(&ctx->proc->io.pending, true, __ATOMIC_RELAXED);
	404	__atomic_store_n(&ctx->proc->io.dirty , true, __ATOMIC_RELAXED);
[2432e8e]	405	}
	406
	407	static inline void __submit( struct $io_context * ctx, __u32 idxs[], __u32 have, bool lazy) {
	408	__sub_ring_t & sq = ctx->sq;
	409	__submit_only(ctx, idxs, have);
	410
[70b4aeb9]	411	if(sq.to_submit > 30) {
	412	__tls_stats()->io.flush.full++;
[18f7858]	413	__cfa_io_flush( ctx->proc );
[70b4aeb9]	414	}
	415	if(!lazy) {
	416	__tls_stats()->io.flush.eager++;
[18f7858]	417	__cfa_io_flush( ctx->proc );
[dddb3dd0]	418	}
[78da4ab]	419	}
[2489d31]	420
[dddb3dd0]	421	void cfa_io_submit( struct $io_context * inctx, __u32 idxs[], __u32 have, bool lazy ) __attribute__((nonnull (1))) {
[1e6ffb44]	422	// __cfadbg_print_safe(io, "Kernel I/O : attempting to submit %u (%s)\n", have, lazy ? "lazy" : "eager");
[5dadc9b7]	423
[78da4ab]	424	disable_interrupts();
	425	processor * proc = __cfaabi_tls.this_processor;
	426	$io_context * ctx = proc->io.ctx;
[dddb3dd0]	427	/* paranoid */ verify( __cfaabi_tls.this_processor );
	428	/* paranoid */ verify( ctx );
[e46c753]	429
[78da4ab]	430	// Can we proceed to the fast path
[dddb3dd0]	431	if( ctx == inctx ) // We have the right instance?
[78da4ab]	432	{
[dddb3dd0]	433	__submit(ctx, idxs, have, lazy);
[e46c753]	434
[78da4ab]	435	// Mark the instance as no longer in-use, re-enable interrupts and return
[d60d30e]	436	__STATS__( true, io.submit.fast += 1; )
[a3821fa]	437	enable_interrupts();
[ece0e80]	438
[1e6ffb44]	439	// __cfadbg_print_safe(io, "Kernel I/O : submitted on fast path\n");
[78da4ab]	440	return;
[e46c753]	441	}
[d384787]	442
[78da4ab]	443	// Fast path failed, fallback on arbitration
[d60d30e]	444	__STATS__( true, io.submit.slow += 1; )
[a3821fa]	445	enable_interrupts();
[5dadc9b7]	446
[1e6ffb44]	447	// __cfadbg_print_safe(io, "Kernel I/O : falling back on arbiter for submission\n");
[426f60c]	448
[11054eb]	449	__ioarbiter_submit(inctx, idxs, have, lazy);
[78da4ab]	450	}
[2fab24e3]	451
[78da4ab]	452	//=============================================================================================
	453	// Flushing
[426f60c]	454	// Go through the ring's submit queue and release everything that has already been consumed
	455	// by io_uring
[78da4ab]	456	// This cannot be done by multiple threads
	457	static __u32 __release_sqes( struct $io_context & ctx ) {
	458	const __u32 mask = *ctx.sq.mask;
[732b406]	459
[426f60c]	460	__attribute__((unused))
[78da4ab]	461	__u32 ctail = *ctx.sq.kring.tail; // get the current tail of the queue
	462	__u32 chead = *ctx.sq.kring.head; // get the current head of the queue
	463	__u32 phead = ctx.sq.kring.released; // get the head the last time we were here
	464
	465	__u32 ftail = ctx.sq.free_ring.tail; // get the current tail of the queue
[732b406]	466
[426f60c]	467	// the 3 fields are organized like this diagram
	468	// except it's are ring
	469	// ---+--------+--------+----
	470	// ---+--------+--------+----
	471	// ^ ^ ^
	472	// phead chead ctail
	473
	474	// make sure ctail doesn't wrap around and reach phead
	475	/* paranoid */ verify(
	476	(ctail >= chead && chead >= phead)
	477	\|\| (chead >= phead && phead >= ctail)
	478	\|\| (phead >= ctail && ctail >= chead)
	479	);
	480
	481	// find the range we need to clear
[4998155]	482	__u32 count = chead - phead;
[426f60c]	483
[78da4ab]	484	if(count == 0) {
	485	return 0;
	486	}
	487
[426f60c]	488	// We acquired an previous-head/current-head range
	489	// go through the range and release the sqes
[34b61882]	490	for( i; count ) {
[1e6ffb44]	491	// __cfadbg_print_safe(io, "Kernel I/O : release loop\n");
[78da4ab]	492	__u32 idx = ctx.sq.kring.array[ (phead + i) & mask ];
	493	ctx.sq.free_ring.array[ (ftail + i) & mask ] = idx;
[34b61882]	494	}
[78da4ab]	495
	496	ctx.sq.kring.released = chead; // note up to were we processed
	497	__atomic_store_n(&ctx.sq.free_ring.tail, ftail + count, __ATOMIC_SEQ_CST);
	498
	499	__ioarbiter_notify(ctx);
	500
[34b61882]	501	return count;
	502	}
[35285fd]	503
[78da4ab]	504	//=============================================================================================
	505	// I/O Arbiter
	506	//=============================================================================================
[9f5a71eb]	507	static inline bool enqueue(__outstanding_io_queue & queue, __outstanding_io & item) {
	508	bool was_empty;
	509
[11054eb]	510	// Lock the list, it's not thread safe
	511	lock( queue.lock __cfaabi_dbg_ctx2 );
	512	{
[9f5a71eb]	513	was_empty = empty(queue.queue);
	514
[11054eb]	515	// Add our request to the list
	516	add( queue.queue, item );
	517
	518	// Mark as pending
	519	__atomic_store_n( &queue.empty, false, __ATOMIC_SEQ_CST );
	520	}
	521	unlock( queue.lock );
	522
[9f5a71eb]	523	return was_empty;
[11054eb]	524	}
	525
	526	static inline bool empty(__outstanding_io_queue & queue ) {
	527	return __atomic_load_n( &queue.empty, __ATOMIC_SEQ_CST);
	528	}
	529
	530	static $io_context * __ioarbiter_allocate( $io_arbiter & this, __u32 idxs[], __u32 want ) {
[1e6ffb44]	531	// __cfadbg_print_safe(io, "Kernel I/O : arbiter allocating\n");
[78da4ab]	532
[d60d30e]	533	__STATS__( false, io.alloc.block += 1; )
	534
[78da4ab]	535	// No one has any resources left, wait for something to finish
[11054eb]	536	// We need to add ourself to a list of pending allocs and wait for an answer
	537	__pending_alloc pa;
	538	pa.idxs = idxs;
	539	pa.want = want;
[78da4ab]	540
[9f5a71eb]	541	enqueue(this.pending, (__outstanding_io&)pa);
	542
	543	wait( pa.sem );
[78da4ab]	544
[11054eb]	545	return pa.ctx;
[dddb3dd0]	546
[78da4ab]	547	}
	548
[11054eb]	549	static void __ioarbiter_notify( $io_arbiter & this, $io_context * ctx ) {
	550	/* paranoid */ verify( !empty(this.pending.queue) );
[78da4ab]	551
[11054eb]	552	lock( this.pending.lock __cfaabi_dbg_ctx2 );
	553	{
	554	while( !empty(this.pending.queue) ) {
	555	__cfadbg_print_safe(io, "Kernel I/O : notifying\n");
	556	__u32 have = ctx->sq.free_ring.tail - ctx->sq.free_ring.head;
	557	__pending_alloc & pa = (__pending_alloc&)head( this.pending.queue );
[78da4ab]	558
[11054eb]	559	if( have > pa.want ) goto DONE;
	560	drop( this.pending.queue );
[78da4ab]	561
[11054eb]	562	/* paranoid */__attribute__((unused)) bool ret =
[78da4ab]	563
[11054eb]	564	__alloc(ctx, pa.idxs, pa.want);
	565
	566	/* paranoid */ verify( ret );
	567
	568	pa.ctx = ctx;
	569
	570	post( pa.sem );
	571	}
	572
	573	this.pending.empty = true;
	574	DONE:;
	575	}
	576	unlock( this.pending.lock );
[78da4ab]	577	}
	578
	579	static void __ioarbiter_notify( $io_context & ctx ) {
[11054eb]	580	if(!empty( ctx.arbiter->pending )) {
[78da4ab]	581	__ioarbiter_notify( *ctx.arbiter, &ctx );
	582	}
	583	}
	584
	585	// Simply append to the pending
[11054eb]	586	static void __ioarbiter_submit( $io_context * ctx, __u32 idxs[], __u32 have, bool lazy ) {
[78da4ab]	587	__cfadbg_print_safe(io, "Kernel I/O : submitting %u from the arbiter to context %u\n", have, ctx->fd);
	588
	589	__cfadbg_print_safe(io, "Kernel I/O : waiting to submit %u\n", have);
	590
[11054eb]	591	__external_io ei;
	592	ei.idxs = idxs;
	593	ei.have = have;
	594	ei.lazy = lazy;
[78da4ab]	595
[9f5a71eb]	596	bool we = enqueue(ctx->ext_sq, (__outstanding_io&)ei);
	597
[d529ad0]	598	__atomic_store_n(&ctx->proc->io.pending, true, __ATOMIC_SEQ_CST);
[9f5a71eb]	599
	600	if( we ) {
	601	sigval_t value = { PREEMPT_IO };
	602	pthread_sigqueue(ctx->proc->kernel_thread, SIGUSR1, value);
	603	}
	604
	605	wait( ei.sem );
[78da4ab]	606
	607	__cfadbg_print_safe(io, "Kernel I/O : %u submitted from arbiter\n", have);
	608	}
	609
[11054eb]	610	static void __ioarbiter_flush( $io_context & ctx ) {
	611	if(!empty( ctx.ext_sq )) {
	612	__STATS__( false, io.flush.external += 1; )
[78da4ab]	613
[11054eb]	614	__cfadbg_print_safe(io, "Kernel I/O : arbiter flushing\n");
[d60d30e]	615
[11054eb]	616	lock( ctx.ext_sq.lock __cfaabi_dbg_ctx2 );
	617	{
	618	while( !empty(ctx.ext_sq.queue) ) {
	619	__external_io & ei = (__external_io&)drop( ctx.ext_sq.queue );
[78da4ab]	620
[2432e8e]	621	__submit_only(&ctx, ei.idxs, ei.have);
[78da4ab]	622
[11054eb]	623	post( ei.sem );
	624	}
	625
	626	ctx.ext_sq.empty = true;
	627	}
	628	unlock(ctx.ext_sq.lock );
	629	}
[78da4ab]	630	}
[7ef162b2]	631
[d3605f8]	632	#if defined(CFA_WITH_IO_URING_IDLE)
	633	bool __kernel_read(processor * proc, io_future_t & future, iovec & iov, int fd) {
[6ddef36]	634	$io_context * ctx = proc->io.ctx;
	635	/* paranoid */ verify( ! __preemption_enabled() );
	636	/* paranoid */ verify( proc == __cfaabi_tls.this_processor );
	637	/* paranoid */ verify( ctx );
[7ef162b2]	638
[6ddef36]	639	__u32 idx;
	640	struct io_uring_sqe * sqe;
[7ef162b2]	641
[6ddef36]	642	// We can proceed to the fast path
[010636f]	643	if( !__alloc(ctx, &idx, 1) ) {
	644	/* paranoid */ verify( false ); // for now check if this happens, next time just abort the sleep.
	645	return false;
	646	}
[6ddef36]	647
	648	// Allocation was successful
	649	__fill( &sqe, 1, &idx, ctx );
	650
	651	sqe->user_data = (uintptr_t)&future;
	652	sqe->flags = 0;
[a1f3d93]	653	sqe->fd = fd;
[6ddef36]	654	sqe->off = 0;
[d3605f8]	655	sqe->ioprio = 0;
[6ddef36]	656	sqe->fsync_flags = 0;
	657	sqe->__pad2[0] = 0;
	658	sqe->__pad2[1] = 0;
	659	sqe->__pad2[2] = 0;
[d3605f8]	660
	661	#if defined(CFA_HAVE_IORING_OP_READ)
	662	sqe->opcode = IORING_OP_READ;
	663	sqe->addr = (uint64_t)iov.iov_base;
	664	sqe->len = iov.iov_len;
	665	#elif defined(CFA_HAVE_READV) && defined(CFA_HAVE_IORING_OP_READV)
	666	sqe->opcode = IORING_OP_READV;
	667	sqe->addr = (uintptr_t)&iov;
	668	sqe->len = 1;
	669	#else
	670	#error CFA_WITH_IO_URING_IDLE but none of CFA_HAVE_READV, CFA_HAVE_IORING_OP_READV or CFA_HAVE_IORING_OP_READ defined
	671	#endif
[6ddef36]	672
	673	asm volatile("": : :"memory");
	674
	675	/* paranoid */ verify( sqe->user_data == (uintptr_t)&future );
[010636f]	676	__submit_only( ctx, &idx, 1 );
[6ddef36]	677
	678	/* paranoid */ verify( proc == __cfaabi_tls.this_processor );
	679	/* paranoid */ verify( ! __preemption_enabled() );
[078fb05]	680
	681	return true;
[6ddef36]	682	}
[18f7858]	683
	684	void __cfa_io_idle( processor * proc ) {
	685	iovec iov;
	686	__atomic_acquire( &proc->io.ctx->cq.lock );
	687
[262fafd9]	688	__attribute__((used)) volatile bool was_reset = false;
	689
[d5cdbed]	690	with( proc->idle_wctx) {
[18f7858]	691
[37a3aa23]	692	// Do we already have a pending read
	693	if(available(*ftr)) {
	694	// There is no pending read, we need to add one
	695	reset(*ftr);
	696
	697	iov.iov_base = rdbuf;
	698	iov.iov_len = sizeof(eventfd_t);
	699	__kernel_read(proc, *ftr, iov, evfd );
[262fafd9]	700	ftr->result = 0xDEADDEAD;
	701	((eventfd_t )rdbuf) = 0xDEADDEADDEADDEAD;
	702	was_reset = true;
[37a3aa23]	703	}
[18f7858]	704	}
	705
[010636f]	706	if( !__atomic_load_n( &proc->do_terminate, __ATOMIC_SEQ_CST ) ) {
	707	__ioarbiter_flush( *proc->io.ctx );
[262fafd9]	708	proc->idle_wctx.sleep_time = rdtscl();
[010636f]	709	ioring_syscsll( *proc->io.ctx, 1, IORING_ENTER_GETEVENTS);
	710	}
[18f7858]	711
[d5cdbed]	712	ready_schedule_lock();
[18f7858]	713	__cfa_do_drain( proc->io.ctx, proc->cltr );
[d5cdbed]	714	ready_schedule_unlock();
[262fafd9]	715
	716	asm volatile ("" :: "m" (was_reset));
[18f7858]	717	}
[6ddef36]	718	#endif
[47746a2]	719	#endif

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