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io.cfa @ ea837e94

ADTarm-ehast-experimentalenumforall-pointer-decayjacob/cs343-translationnew-ast-unique-exprpthread-emulationqualifiedEnum

Last change on this file since ea837e94 was dddb3dd0, checked in by Thierry Delisle <tdelisle@…>, 4 years ago
Changed io to use ring per kernel threads.
Property mode set to `100644`
File size: 14.6 KB

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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
16	#define __cforall_thread__
17
18	#if defined(__CFA_DEBUG__)
19	// #define __CFA_DEBUG_PRINT_IO__
20	// #define __CFA_DEBUG_PRINT_IO_CORE__
21	#endif
22
23
24	#if defined(CFA_HAVE_LINUX_IO_URING_H)
25	#define _GNU_SOURCE /* See feature_test_macros(7) */
26	#include <errno.h>
27	#include <signal.h>
28	#include <stdint.h>
29	#include <string.h>
30	#include <unistd.h>
31
32	extern "C" {
33	#include <sys/syscall.h>
34	#include <sys/eventfd.h>
35
36	#include <linux/io_uring.h>
37	}
38
39	#include "stats.hfa"
40	#include "kernel.hfa"
41	#include "kernel/fwd.hfa"
42	#include "io/types.hfa"
43
44	__attribute__((unused)) static const char * opcodes[] = {
45	"OP_NOP",
46	"OP_READV",
47	"OP_WRITEV",
48	"OP_FSYNC",
49	"OP_READ_FIXED",
50	"OP_WRITE_FIXED",
51	"OP_POLL_ADD",
52	"OP_POLL_REMOVE",
53	"OP_SYNC_FILE_RANGE",
54	"OP_SENDMSG",
55	"OP_RECVMSG",
56	"OP_TIMEOUT",
57	"OP_TIMEOUT_REMOVE",
58	"OP_ACCEPT",
59	"OP_ASYNC_CANCEL",
60	"OP_LINK_TIMEOUT",
61	"OP_CONNECT",
62	"OP_FALLOCATE",
63	"OP_OPENAT",
64	"OP_CLOSE",
65	"OP_FILES_UPDATE",
66	"OP_STATX",
67	"OP_READ",
68	"OP_WRITE",
69	"OP_FADVISE",
70	"OP_MADVISE",
71	"OP_SEND",
72	"OP_RECV",
73	"OP_OPENAT2",
74	"OP_EPOLL_CTL",
75	"OP_SPLICE",
76	"OP_PROVIDE_BUFFERS",
77	"OP_REMOVE_BUFFERS",
78	"OP_TEE",
79	"INVALID_OP"
80	};
81
82	static $io_context * __ioarbiter_allocate( $io_arbiter & mutex this, processor *, __u32 idxs[], __u32 want );
83	static void __ioarbiter_submit( $io_arbiter & mutex this, $io_context * , __u32 idxs[], __u32 have, bool lazy );
84	static void __ioarbiter_flush ( $io_arbiter & mutex this, $io_context * );
85	static inline void __ioarbiter_notify( $io_context & ctx );
86	//=============================================================================================
87	// I/O Polling
88	//=============================================================================================
89	static inline unsigned __flush( struct $io_context & );
90	static inline __u32 __release_sqes( struct $io_context & );
91
92	void __cfa_io_drain( processor * proc ) {
93	/* paranoid */ verify( ! __preemption_enabled() );
94	/* paranoid */ verify( proc );
95	/* paranoid */ verify( proc->io.ctx );
96
97	// Drain the queue
98	$io_context * ctx = proc->io.ctx;
99	unsigned head = *ctx->cq.head;
100	unsigned tail = *ctx->cq.tail;
101	const __u32 mask = *ctx->cq.mask;
102
103	__u32 count = tail - head;
104	__STATS__( false, io.calls.drain++; io.calls.completed += count; )
105
106	for(i; count) {
107	unsigned idx = (head + i) & mask;
108	volatile struct io_uring_cqe & cqe = ctx->cq.cqes[idx];
109
110	/* paranoid */ verify(&cqe);
111
112	struct io_future_t * future = (struct io_future_t *)(uintptr_t)cqe.user_data;
113	__cfadbg_print_safe( io, "Kernel I/O : Syscall completed : cqe %p, result %d for %p\n", &cqe, cqe.res, future );
114
115	fulfil( *future, cqe.res );
116	}
117
118	__cfadbg_print_safe(io, "Kernel I/O : %u completed\n", count);
119
120	// Mark to the kernel that the cqe has been seen
121	// Ensure that the kernel only sees the new value of the head index after the CQEs have been read.
122	__atomic_store_n( ctx->cq.head, head + count, __ATOMIC_SEQ_CST );
123
124	/* paranoid */ verify( ! __preemption_enabled() );
125
126	return;
127	}
128
129	void __cfa_io_flush( processor * proc ) {
130	/* paranoid */ verify( ! __preemption_enabled() );
131	/* paranoid */ verify( proc );
132	/* paranoid */ verify( proc->io.ctx );
133
134	$io_context & ctx = *proc->io.ctx;
135
136	if(!ctx.ext_sq.empty) {
137	__ioarbiter_flush( *ctx.arbiter, &ctx );
138	}
139
140	__STATS__( true, io.calls.flush++; )
141	int ret = syscall( __NR_io_uring_enter, ctx.fd, ctx.sq.to_submit, 0, 0, (sigset_t *)0p, _NSIG / 8);
142	if( ret < 0 ) {
143	switch((int)errno) {
144	case EAGAIN:
145	case EINTR:
146	case EBUSY:
147	// Update statistics
148	__STATS__( false, io.calls.errors.busy ++; )
149	return;
150	default:
151	abort( "KERNEL ERROR: IO_URING SYSCALL - (%d) %s\n", (int)errno, strerror(errno) );
152	}
153	}
154
155	__cfadbg_print_safe(io, "Kernel I/O : %u submitted to io_uring %d\n", ret, ctx.fd);
156	__STATS__( true, io.calls.submitted += ret; )
157	/* paranoid / verify( ctx.sq.to_submit <= ctx.sq.num );
158	/* paranoid */ verify( ctx.sq.to_submit >= ret );
159
160	ctx.sq.to_submit -= ret;
161
162	/* paranoid / verify( ctx.sq.to_submit <= ctx.sq.num );
163
164	// Release the consumed SQEs
165	__release_sqes( ctx );
166
167	/* paranoid */ verify( ! __preemption_enabled() );
168
169	ctx.proc->io.pending = false;
170	}
171
172	//=============================================================================================
173	// I/O Submissions
174	//=============================================================================================
175
176	// Submition steps :
177	// 1 - Allocate a queue entry. The ring already has memory for all entries but only the ones
178	// listed in sq.array are visible by the kernel. For those not listed, the kernel does not
179	// offer any assurance that an entry is not being filled by multiple flags. Therefore, we
180	// need to write an allocator that allows allocating concurrently.
181	//
182	// 2 - Actually fill the submit entry, this is the only simple and straightforward step.
183	//
184	// 3 - Append the entry index to the array and adjust the tail accordingly. This operation
185	// needs to arrive to two concensus at the same time:
186	// A - The order in which entries are listed in the array: no two threads must pick the
187	// same index for their entries
188	// B - When can the tail be update for the kernel. EVERY entries in the array between
189	// head and tail must be fully filled and shouldn't ever be touched again.
190	//
191	//=============================================================================================
192	// Allocation
193	// for user's convenience fill the sqes from the indexes
194	static inline void __fill(struct io_uring_sqe * out_sqes[], __u32 want, __u32 idxs[], struct $io_context * ctx) {
195	struct io_uring_sqe * sqes = ctx->sq.sqes;
196	for(i; want) {
197	__cfadbg_print_safe(io, "Kernel I/O : filling loop\n");
198	out_sqes[i] = &sqes[idxs[i]];
199	}
200	}
201
202	// Try to directly allocate from the a given context
203	// Not thread-safe
204	static inline bool __alloc(struct $io_context * ctx, __u32 idxs[], __u32 want) {
205	__sub_ring_t & sq = ctx->sq;
206	const __u32 mask = *sq.mask;
207	__u32 fhead = sq.free_ring.head; // get the current head of the queue
208	__u32 ftail = sq.free_ring.tail; // get the current tail of the queue
209
210	// If we don't have enough sqes, fail
211	if((ftail - fhead) < want) { return false; }
212
213	// copy all the indexes we want from the available list
214	for(i; want) {
215	__cfadbg_print_safe(io, "Kernel I/O : allocating loop\n");
216	idxs[i] = sq.free_ring.array[(fhead + i) & mask];
217	}
218
219	// Advance the head to mark the indexes as consumed
220	__atomic_store_n(&sq.free_ring.head, fhead + want, __ATOMIC_RELEASE);
221
222	// return success
223	return true;
224	}
225
226	// Allocate an submit queue entry.
227	// The kernel cannot see these entries until they are submitted, but other threads must be
228	// able to see which entries can be used and which are already un used by an other thread
229	// for convenience, return both the index and the pointer to the sqe
230	// sqe == &sqes[idx]
231	struct $io_context * cfa_io_allocate(struct io_uring_sqe * sqes[], __u32 idxs[], __u32 want) {
232	__cfadbg_print_safe(io, "Kernel I/O : attempting to allocate %u\n", want);
233
234	disable_interrupts();
235	processor * proc = __cfaabi_tls.this_processor;
236	$io_context * ctx = proc->io.ctx;
237	/* paranoid */ verify( __cfaabi_tls.this_processor );
238	/* paranoid */ verify( ctx );
239
240	__cfadbg_print_safe(io, "Kernel I/O : attempting to fast allocation\n");
241
242	// We can proceed to the fast path
243	if( __alloc(ctx, idxs, want) ) {
244	// Allocation was successful
245	__STATS__( true, io.alloc.fast += 1; )
246	enable_interrupts( __cfaabi_dbg_ctx );
247
248	__cfadbg_print_safe(io, "Kernel I/O : fast allocation successful from ring %d\n", ctx->fd);
249
250	__fill( sqes, want, idxs, ctx );
251	return ctx;
252	}
253	// The fast path failed, fallback
254	__STATS__( true, io.alloc.fail += 1; )
255
256	// Fast path failed, fallback on arbitration
257	__STATS__( true, io.alloc.slow += 1; )
258	enable_interrupts( __cfaabi_dbg_ctx );
259
260	$io_arbiter * ioarb = proc->cltr->io.arbiter;
261	/* paranoid */ verify( ioarb );
262
263	__cfadbg_print_safe(io, "Kernel I/O : falling back on arbiter for allocation\n");
264
265	struct $io_context * ret = __ioarbiter_allocate(*ioarb, proc, idxs, want);
266
267	__cfadbg_print_safe(io, "Kernel I/O : slow allocation completed from ring %d\n", ret->fd);
268
269	__fill( sqes, want, idxs,ret );
270	return ret;
271	}
272
273
274	//=============================================================================================
275	// submission
276	static inline void __submit( struct $io_context * ctx, __u32 idxs[], __u32 have, bool lazy) {
277	// We can proceed to the fast path
278	// Get the right objects
279	__sub_ring_t & sq = ctx->sq;
280	const __u32 mask = *sq.mask;
281	__u32 tail = *sq.kring.tail;
282
283	// Add the sqes to the array
284	for( i; have ) {
285	__cfadbg_print_safe(io, "Kernel I/O : __submit loop\n");
286	sq.kring.array[ (tail + i) & mask ] = idxs[i];
287	}
288
289	// Make the sqes visible to the submitter
290	__atomic_store_n(sq.kring.tail, tail + have, __ATOMIC_RELEASE);
291	sq.to_submit++;
292
293	ctx->proc->io.pending = true;
294	ctx->proc->io.dirty = true;
295	if(sq.to_submit > 30 \|\| !lazy) {
296	__cfa_io_flush( ctx->proc );
297	}
298	}
299
300	void cfa_io_submit( struct $io_context * inctx, __u32 idxs[], __u32 have, bool lazy ) __attribute__((nonnull (1))) {
301	__cfadbg_print_safe(io, "Kernel I/O : attempting to submit %u (%s)\n", have, lazy ? "lazy" : "eager");
302
303	disable_interrupts();
304	processor * proc = __cfaabi_tls.this_processor;
305	$io_context * ctx = proc->io.ctx;
306	/* paranoid */ verify( __cfaabi_tls.this_processor );
307	/* paranoid */ verify( ctx );
308
309	// Can we proceed to the fast path
310	if( ctx == inctx ) // We have the right instance?
311	{
312	__submit(ctx, idxs, have, lazy);
313
314	// Mark the instance as no longer in-use, re-enable interrupts and return
315	__STATS__( true, io.submit.fast += 1; )
316	enable_interrupts( __cfaabi_dbg_ctx );
317
318	__cfadbg_print_safe(io, "Kernel I/O : submitted on fast path\n");
319	return;
320	}
321
322	// Fast path failed, fallback on arbitration
323	__STATS__( true, io.submit.slow += 1; )
324	enable_interrupts( __cfaabi_dbg_ctx );
325
326	__cfadbg_print_safe(io, "Kernel I/O : falling back on arbiter for submission\n");
327
328	__ioarbiter_submit(*inctx->arbiter, inctx, idxs, have, lazy);
329	}
330
331	//=============================================================================================
332	// Flushing
333	// Go through the ring's submit queue and release everything that has already been consumed
334	// by io_uring
335	// This cannot be done by multiple threads
336	static __u32 __release_sqes( struct $io_context & ctx ) {
337	const __u32 mask = *ctx.sq.mask;
338
339	__attribute__((unused))
340	__u32 ctail = *ctx.sq.kring.tail; // get the current tail of the queue
341	__u32 chead = *ctx.sq.kring.head; // get the current head of the queue
342	__u32 phead = ctx.sq.kring.released; // get the head the last time we were here
343
344	__u32 ftail = ctx.sq.free_ring.tail; // get the current tail of the queue
345
346	// the 3 fields are organized like this diagram
347	// except it's are ring
348	// ---+--------+--------+----
349	// ---+--------+--------+----
350	// ^ ^ ^
351	// phead chead ctail
352
353	// make sure ctail doesn't wrap around and reach phead
354	/* paranoid */ verify(
355	(ctail >= chead && chead >= phead)
356	\|\| (chead >= phead && phead >= ctail)
357	\|\| (phead >= ctail && ctail >= chead)
358	);
359
360	// find the range we need to clear
361	__u32 count = chead - phead;
362
363	if(count == 0) {
364	return 0;
365	}
366
367	// We acquired an previous-head/current-head range
368	// go through the range and release the sqes
369	for( i; count ) {
370	__cfadbg_print_safe(io, "Kernel I/O : release loop\n");
371	__u32 idx = ctx.sq.kring.array[ (phead + i) & mask ];
372	ctx.sq.free_ring.array[ (ftail + i) & mask ] = idx;
373	}
374
375	ctx.sq.kring.released = chead; // note up to were we processed
376	__atomic_store_n(&ctx.sq.free_ring.tail, ftail + count, __ATOMIC_SEQ_CST);
377
378	__ioarbiter_notify(ctx);
379
380	return count;
381	}
382
383	//=============================================================================================
384	// I/O Arbiter
385	//=============================================================================================
386	static $io_context * __ioarbiter_allocate( $io_arbiter & mutex this, processor * proc, __u32 idxs[], __u32 want ) {
387	__cfadbg_print_safe(io, "Kernel I/O : arbiter allocating\n");
388
389	__STATS__( false, io.alloc.block += 1; )
390
391	// No one has any resources left, wait for something to finish
392	// Mark as pending
393	__atomic_store_n( &this.pending.flag, true, __ATOMIC_SEQ_CST );
394
395	// Wait for our turn to submit
396	wait( this.pending.blocked, want );
397
398	__attribute((unused)) bool ret =
399	__alloc( this.pending.ctx, idxs, want);
400	/* paranoid */ verify( ret );
401
402	return this.pending.ctx;
403
404	}
405
406	static void __ioarbiter_notify( $io_arbiter & mutex this, $io_context * ctx ) {
407	/* paranoid */ verify( !is_empty(this.pending.blocked) );
408	this.pending.ctx = ctx;
409
410	while( !is_empty(this.pending.blocked) ) {
411	__cfadbg_print_safe(io, "Kernel I/O : notifying\n");
412	__u32 have = ctx->sq.free_ring.tail - ctx->sq.free_ring.head;
413	__u32 want = front( this.pending.blocked );
414
415	if( have > want ) return;
416
417	signal_block( this.pending.blocked );
418	}
419
420	this.pending.flag = false;
421	}
422
423	static void __ioarbiter_notify( $io_context & ctx ) {
424	if(__atomic_load_n( &ctx.arbiter->pending.flag, __ATOMIC_SEQ_CST)) {
425	__ioarbiter_notify( *ctx.arbiter, &ctx );
426	}
427	}
428
429	// Simply append to the pending
430	static void __ioarbiter_submit( $io_arbiter & mutex this, $io_context * ctx, __u32 idxs[], __u32 have, bool lazy ) {
431	__cfadbg_print_safe(io, "Kernel I/O : submitting %u from the arbiter to context %u\n", have, ctx->fd);
432
433	/* paranoid */ verify( &this == ctx->arbiter );
434
435	// Mark as pending
436	__atomic_store_n( &ctx->ext_sq.empty, false, __ATOMIC_SEQ_CST );
437
438	__cfadbg_print_safe(io, "Kernel I/O : waiting to submit %u\n", have);
439
440	// Wait for our turn to submit
441	wait( ctx->ext_sq.blocked );
442
443	// Submit our indexes
444	__submit(ctx, idxs, have, lazy);
445
446	__cfadbg_print_safe(io, "Kernel I/O : %u submitted from arbiter\n", have);
447	}
448
449	static void __ioarbiter_flush( $io_arbiter & mutex this, $io_context * ctx ) {
450	/* paranoid */ verify( &this == ctx->arbiter );
451
452	__STATS__( false, io.flush.external += 1; )
453
454	__cfadbg_print_safe(io, "Kernel I/O : arbiter flushing\n");
455
456	condition & blcked = ctx->ext_sq.blocked;
457	/* paranoid */ verify( ctx->ext_sq.empty == is_empty( blcked ) );
458	while(!is_empty( blcked )) {
459	signal_block( blcked );
460	}
461
462	ctx->ext_sq.empty = true;
463	}
464	#endif

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