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io.cfa @ a4b0aa4

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

Last change on this file since a4b0aa4 was 11054eb, checked in by Thierry Delisle <tdelisle@…>, 4 years ago
Fix io to no longer use monitors since some usages aren't in threads
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File size: 14.9 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 & this, __u32 idxs[], __u32 want );
83	static void __ioarbiter_submit( $io_context * , __u32 idxs[], __u32 have, bool lazy );
84	static void __ioarbiter_flush ( $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	__ioarbiter_flush( ctx );
137
138	__STATS__( true, io.calls.flush++; )
139	int ret = syscall( __NR_io_uring_enter, ctx.fd, ctx.sq.to_submit, 0, 0, (sigset_t *)0p, _NSIG / 8);
140	if( ret < 0 ) {
141	switch((int)errno) {
142	case EAGAIN:
143	case EINTR:
144	case EBUSY:
145	// Update statistics
146	__STATS__( false, io.calls.errors.busy ++; )
147	return;
148	default:
149	abort( "KERNEL ERROR: IO_URING SYSCALL - (%d) %s\n", (int)errno, strerror(errno) );
150	}
151	}
152
153	__cfadbg_print_safe(io, "Kernel I/O : %u submitted to io_uring %d\n", ret, ctx.fd);
154	__STATS__( true, io.calls.submitted += ret; )
155	/* paranoid / verify( ctx.sq.to_submit <= ctx.sq.num );
156	/* paranoid */ verify( ctx.sq.to_submit >= ret );
157
158	ctx.sq.to_submit -= ret;
159
160	/* paranoid / verify( ctx.sq.to_submit <= ctx.sq.num );
161
162	// Release the consumed SQEs
163	__release_sqes( ctx );
164
165	/* paranoid */ verify( ! __preemption_enabled() );
166
167	ctx.proc->io.pending = false;
168	}
169
170	//=============================================================================================
171	// I/O Submissions
172	//=============================================================================================
173
174	// Submition steps :
175	// 1 - Allocate a queue entry. The ring already has memory for all entries but only the ones
176	// listed in sq.array are visible by the kernel. For those not listed, the kernel does not
177	// offer any assurance that an entry is not being filled by multiple flags. Therefore, we
178	// need to write an allocator that allows allocating concurrently.
179	//
180	// 2 - Actually fill the submit entry, this is the only simple and straightforward step.
181	//
182	// 3 - Append the entry index to the array and adjust the tail accordingly. This operation
183	// needs to arrive to two concensus at the same time:
184	// A - The order in which entries are listed in the array: no two threads must pick the
185	// same index for their entries
186	// B - When can the tail be update for the kernel. EVERY entries in the array between
187	// head and tail must be fully filled and shouldn't ever be touched again.
188	//
189	//=============================================================================================
190	// Allocation
191	// for user's convenience fill the sqes from the indexes
192	static inline void __fill(struct io_uring_sqe * out_sqes[], __u32 want, __u32 idxs[], struct $io_context * ctx) {
193	struct io_uring_sqe * sqes = ctx->sq.sqes;
194	for(i; want) {
195	__cfadbg_print_safe(io, "Kernel I/O : filling loop\n");
196	out_sqes[i] = &sqes[idxs[i]];
197	}
198	}
199
200	// Try to directly allocate from the a given context
201	// Not thread-safe
202	static inline bool __alloc(struct $io_context * ctx, __u32 idxs[], __u32 want) {
203	__sub_ring_t & sq = ctx->sq;
204	const __u32 mask = *sq.mask;
205	__u32 fhead = sq.free_ring.head; // get the current head of the queue
206	__u32 ftail = sq.free_ring.tail; // get the current tail of the queue
207
208	// If we don't have enough sqes, fail
209	if((ftail - fhead) < want) { return false; }
210
211	// copy all the indexes we want from the available list
212	for(i; want) {
213	__cfadbg_print_safe(io, "Kernel I/O : allocating loop\n");
214	idxs[i] = sq.free_ring.array[(fhead + i) & mask];
215	}
216
217	// Advance the head to mark the indexes as consumed
218	__atomic_store_n(&sq.free_ring.head, fhead + want, __ATOMIC_RELEASE);
219
220	// return success
221	return true;
222	}
223
224	// Allocate an submit queue entry.
225	// The kernel cannot see these entries until they are submitted, but other threads must be
226	// able to see which entries can be used and which are already un used by an other thread
227	// for convenience, return both the index and the pointer to the sqe
228	// sqe == &sqes[idx]
229	struct $io_context * cfa_io_allocate(struct io_uring_sqe * sqes[], __u32 idxs[], __u32 want) {
230	__cfadbg_print_safe(io, "Kernel I/O : attempting to allocate %u\n", want);
231
232	disable_interrupts();
233	processor * proc = __cfaabi_tls.this_processor;
234	$io_context * ctx = proc->io.ctx;
235	/* paranoid */ verify( __cfaabi_tls.this_processor );
236	/* paranoid */ verify( ctx );
237
238	__cfadbg_print_safe(io, "Kernel I/O : attempting to fast allocation\n");
239
240	// We can proceed to the fast path
241	if( __alloc(ctx, idxs, want) ) {
242	// Allocation was successful
243	__STATS__( true, io.alloc.fast += 1; )
244	enable_interrupts( __cfaabi_dbg_ctx );
245
246	__cfadbg_print_safe(io, "Kernel I/O : fast allocation successful from ring %d\n", ctx->fd);
247
248	__fill( sqes, want, idxs, ctx );
249	return ctx;
250	}
251	// The fast path failed, fallback
252	__STATS__( true, io.alloc.fail += 1; )
253
254	// Fast path failed, fallback on arbitration
255	__STATS__( true, io.alloc.slow += 1; )
256	enable_interrupts( __cfaabi_dbg_ctx );
257
258	$io_arbiter * ioarb = proc->cltr->io.arbiter;
259	/* paranoid */ verify( ioarb );
260
261	__cfadbg_print_safe(io, "Kernel I/O : falling back on arbiter for allocation\n");
262
263	struct $io_context * ret = __ioarbiter_allocate(*ioarb, idxs, want);
264
265	__cfadbg_print_safe(io, "Kernel I/O : slow allocation completed from ring %d\n", ret->fd);
266
267	__fill( sqes, want, idxs,ret );
268	return ret;
269	}
270
271
272	//=============================================================================================
273	// submission
274	static inline void __submit( struct $io_context * ctx, __u32 idxs[], __u32 have, bool lazy) {
275	// We can proceed to the fast path
276	// Get the right objects
277	__sub_ring_t & sq = ctx->sq;
278	const __u32 mask = *sq.mask;
279	__u32 tail = *sq.kring.tail;
280
281	// Add the sqes to the array
282	for( i; have ) {
283	__cfadbg_print_safe(io, "Kernel I/O : __submit loop\n");
284	sq.kring.array[ (tail + i) & mask ] = idxs[i];
285	}
286
287	// Make the sqes visible to the submitter
288	__atomic_store_n(sq.kring.tail, tail + have, __ATOMIC_RELEASE);
289	sq.to_submit++;
290
291	ctx->proc->io.pending = true;
292	ctx->proc->io.dirty = true;
293	if(sq.to_submit > 30 \|\| !lazy) {
294	__cfa_io_flush( ctx->proc );
295	}
296	}
297
298	void cfa_io_submit( struct $io_context * inctx, __u32 idxs[], __u32 have, bool lazy ) __attribute__((nonnull (1))) {
299	__cfadbg_print_safe(io, "Kernel I/O : attempting to submit %u (%s)\n", have, lazy ? "lazy" : "eager");
300
301	disable_interrupts();
302	processor * proc = __cfaabi_tls.this_processor;
303	$io_context * ctx = proc->io.ctx;
304	/* paranoid */ verify( __cfaabi_tls.this_processor );
305	/* paranoid */ verify( ctx );
306
307	// Can we proceed to the fast path
308	if( ctx == inctx ) // We have the right instance?
309	{
310	__submit(ctx, idxs, have, lazy);
311
312	// Mark the instance as no longer in-use, re-enable interrupts and return
313	__STATS__( true, io.submit.fast += 1; )
314	enable_interrupts( __cfaabi_dbg_ctx );
315
316	__cfadbg_print_safe(io, "Kernel I/O : submitted on fast path\n");
317	return;
318	}
319
320	// Fast path failed, fallback on arbitration
321	__STATS__( true, io.submit.slow += 1; )
322	enable_interrupts( __cfaabi_dbg_ctx );
323
324	__cfadbg_print_safe(io, "Kernel I/O : falling back on arbiter for submission\n");
325
326	__ioarbiter_submit(inctx, idxs, have, lazy);
327	}
328
329	//=============================================================================================
330	// Flushing
331	// Go through the ring's submit queue and release everything that has already been consumed
332	// by io_uring
333	// This cannot be done by multiple threads
334	static __u32 __release_sqes( struct $io_context & ctx ) {
335	const __u32 mask = *ctx.sq.mask;
336
337	__attribute__((unused))
338	__u32 ctail = *ctx.sq.kring.tail; // get the current tail of the queue
339	__u32 chead = *ctx.sq.kring.head; // get the current head of the queue
340	__u32 phead = ctx.sq.kring.released; // get the head the last time we were here
341
342	__u32 ftail = ctx.sq.free_ring.tail; // get the current tail of the queue
343
344	// the 3 fields are organized like this diagram
345	// except it's are ring
346	// ---+--------+--------+----
347	// ---+--------+--------+----
348	// ^ ^ ^
349	// phead chead ctail
350
351	// make sure ctail doesn't wrap around and reach phead
352	/* paranoid */ verify(
353	(ctail >= chead && chead >= phead)
354	\|\| (chead >= phead && phead >= ctail)
355	\|\| (phead >= ctail && ctail >= chead)
356	);
357
358	// find the range we need to clear
359	__u32 count = chead - phead;
360
361	if(count == 0) {
362	return 0;
363	}
364
365	// We acquired an previous-head/current-head range
366	// go through the range and release the sqes
367	for( i; count ) {
368	__cfadbg_print_safe(io, "Kernel I/O : release loop\n");
369	__u32 idx = ctx.sq.kring.array[ (phead + i) & mask ];
370	ctx.sq.free_ring.array[ (ftail + i) & mask ] = idx;
371	}
372
373	ctx.sq.kring.released = chead; // note up to were we processed
374	__atomic_store_n(&ctx.sq.free_ring.tail, ftail + count, __ATOMIC_SEQ_CST);
375
376	__ioarbiter_notify(ctx);
377
378	return count;
379	}
380
381	//=============================================================================================
382	// I/O Arbiter
383	//=============================================================================================
384	static inline void block(__outstanding_io_queue & queue, __outstanding_io & item) {
385	// Lock the list, it's not thread safe
386	lock( queue.lock __cfaabi_dbg_ctx2 );
387	{
388	// Add our request to the list
389	add( queue.queue, item );
390
391	// Mark as pending
392	__atomic_store_n( &queue.empty, false, __ATOMIC_SEQ_CST );
393	}
394	unlock( queue.lock );
395
396	wait( item.sem );
397	}
398
399	static inline bool empty(__outstanding_io_queue & queue ) {
400	return __atomic_load_n( &queue.empty, __ATOMIC_SEQ_CST);
401	}
402
403	static $io_context * __ioarbiter_allocate( $io_arbiter & this, __u32 idxs[], __u32 want ) {
404	__cfadbg_print_safe(io, "Kernel I/O : arbiter allocating\n");
405
406	__STATS__( false, io.alloc.block += 1; )
407
408	// No one has any resources left, wait for something to finish
409	// We need to add ourself to a list of pending allocs and wait for an answer
410	__pending_alloc pa;
411	pa.idxs = idxs;
412	pa.want = want;
413
414	block(this.pending, (__outstanding_io&)pa);
415
416	return pa.ctx;
417
418	}
419
420	static void __ioarbiter_notify( $io_arbiter & this, $io_context * ctx ) {
421	/* paranoid */ verify( !empty(this.pending.queue) );
422
423	lock( this.pending.lock __cfaabi_dbg_ctx2 );
424	{
425	while( !empty(this.pending.queue) ) {
426	__cfadbg_print_safe(io, "Kernel I/O : notifying\n");
427	__u32 have = ctx->sq.free_ring.tail - ctx->sq.free_ring.head;
428	__pending_alloc & pa = (__pending_alloc&)head( this.pending.queue );
429
430	if( have > pa.want ) goto DONE;
431	drop( this.pending.queue );
432
433	/* paranoid */__attribute__((unused)) bool ret =
434
435	__alloc(ctx, pa.idxs, pa.want);
436
437	/* paranoid */ verify( ret );
438
439	pa.ctx = ctx;
440
441	post( pa.sem );
442	}
443
444	this.pending.empty = true;
445	DONE:;
446	}
447	unlock( this.pending.lock );
448	}
449
450	static void __ioarbiter_notify( $io_context & ctx ) {
451	if(!empty( ctx.arbiter->pending )) {
452	__ioarbiter_notify( *ctx.arbiter, &ctx );
453	}
454	}
455
456	// Simply append to the pending
457	static void __ioarbiter_submit( $io_context * ctx, __u32 idxs[], __u32 have, bool lazy ) {
458	__cfadbg_print_safe(io, "Kernel I/O : submitting %u from the arbiter to context %u\n", have, ctx->fd);
459
460	__cfadbg_print_safe(io, "Kernel I/O : waiting to submit %u\n", have);
461
462	__external_io ei;
463	ei.idxs = idxs;
464	ei.have = have;
465	ei.lazy = lazy;
466
467	block(ctx->ext_sq, (__outstanding_io&)ei);
468
469	__cfadbg_print_safe(io, "Kernel I/O : %u submitted from arbiter\n", have);
470	}
471
472	static void __ioarbiter_flush( $io_context & ctx ) {
473	if(!empty( ctx.ext_sq )) {
474	__STATS__( false, io.flush.external += 1; )
475
476	__cfadbg_print_safe(io, "Kernel I/O : arbiter flushing\n");
477
478	lock( ctx.ext_sq.lock __cfaabi_dbg_ctx2 );
479	{
480	while( !empty(ctx.ext_sq.queue) ) {
481	__external_io & ei = (__external_io&)drop( ctx.ext_sq.queue );
482
483	__submit(&ctx, ei.idxs, ei.have, ei.lazy);
484
485	post( ei.sem );
486	}
487
488	ctx.ext_sq.empty = true;
489	}
490	unlock(ctx.ext_sq.lock );
491	}
492	}
493	#endif

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