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io.cfa @ 20ab637

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

Last change on this file since 20ab637 was 20ab637, checked in by Thierry Delisle <tdelisle@…>, 5 years ago
Added quick and dirty support for fixed files reads. Added support for kernel side polling.
Property mode set to `100644`
File size: 29.8 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	#if defined(__CFA_DEBUG__)
17	// #define __CFA_DEBUG_PRINT_IO__
18	#define __CFA_DEBUG_PRINT_IO_CORE__
19	#endif
20
21	#include "kernel.hfa"
22	#include "bitmanip.hfa"
23
24	#if !defined(HAVE_LINUX_IO_URING_H)
25	void __kernel_io_startup( cluster &, unsigned, bool ) {
26	// Nothing to do without io_uring
27	}
28
29	void __kernel_io_finish_start( cluster & ) {
30	// Nothing to do without io_uring
31	}
32
33	void __kernel_io_prepare_stop( cluster & ) {
34	// Nothing to do without io_uring
35	}
36
37	void __kernel_io_shutdown( cluster &, bool ) {
38	// Nothing to do without io_uring
39	}
40
41	#else
42	#define _GNU_SOURCE /* See feature_test_macros(7) */
43	#include <errno.h>
44	#include <stdint.h>
45	#include <string.h>
46	#include <unistd.h>
47	#include <sys/mman.h>
48
49	extern "C" {
50	#include <sys/syscall.h>
51
52	#include <linux/io_uring.h>
53	}
54
55	#include "bits/signal.hfa"
56	#include "kernel_private.hfa"
57	#include "thread.hfa"
58
59	uint32_t entries_per_cluster() {
60	return 256;
61	}
62
63	static void * __io_poller_slow( void * arg );
64
65	// Weirdly, some systems that do support io_uring don't actually define these
66	#ifdef __alpha__
67	/*
68	* alpha is the only exception, all other architectures
69	* have common numbers for new system calls.
70	*/
71	#ifndef __NR_io_uring_setup
72	#define __NR_io_uring_setup 535
73	#endif
74	#ifndef __NR_io_uring_enter
75	#define __NR_io_uring_enter 536
76	#endif
77	#ifndef __NR_io_uring_register
78	#define __NR_io_uring_register 537
79	#endif
80	#else /* !__alpha__ */
81	#ifndef __NR_io_uring_setup
82	#define __NR_io_uring_setup 425
83	#endif
84	#ifndef __NR_io_uring_enter
85	#define __NR_io_uring_enter 426
86	#endif
87	#ifndef __NR_io_uring_register
88	#define __NR_io_uring_register 427
89	#endif
90	#endif
91
92	// Fast poller user-thread
93	// Not using the "thread" keyword because we want to control
94	// more carefully when to start/stop it
95	struct __io_poller_fast {
96	struct __io_data * ring;
97	$thread thrd;
98	};
99
100	void ?{}( __io_poller_fast & this, struct cluster & cltr ) {
101	this.ring = cltr.io;
102	(this.thrd){ "Fast I/O Poller", cltr };
103	}
104	void ^?{}( __io_poller_fast & mutex this );
105	void main( __io_poller_fast & this );
106	static inline $thread * get_thread( __io_poller_fast & this ) { return &this.thrd; }
107	void ^?{}( __io_poller_fast & mutex this ) {}
108
109	struct __submition_data {
110	// Head and tail of the ring (associated with array)
111	volatile uint32_t * head;
112	volatile uint32_t * tail;
113	volatile uint32_t prev_head;
114
115	// The actual kernel ring which uses head/tail
116	// indexes into the sqes arrays
117	uint32_t * array;
118
119	// number of entries and mask to go with it
120	const uint32_t * num;
121	const uint32_t * mask;
122
123	// Submission flags (Not sure what for)
124	uint32_t * flags;
125
126	// number of sqes not submitted (whatever that means)
127	uint32_t * dropped;
128
129	// Like head/tail but not seen by the kernel
130	volatile uint32_t * ready;
131	uint32_t ready_cnt;
132
133	__spinlock_t lock;
134	__spinlock_t release_lock;
135
136	// A buffer of sqes (not the actual ring)
137	struct io_uring_sqe * sqes;
138
139	// The location and size of the mmaped area
140	void * ring_ptr;
141	size_t ring_sz;
142	};
143
144	struct __completion_data {
145	// Head and tail of the ring
146	volatile uint32_t * head;
147	volatile uint32_t * tail;
148
149	// number of entries and mask to go with it
150	const uint32_t * mask;
151	const uint32_t * num;
152
153	// number of cqes not submitted (whatever that means)
154	uint32_t * overflow;
155
156	// the kernel ring
157	struct io_uring_cqe * cqes;
158
159	// The location and size of the mmaped area
160	void * ring_ptr;
161	size_t ring_sz;
162	};
163
164	struct __io_data {
165	struct __submition_data submit_q;
166	struct __completion_data completion_q;
167	uint32_t ring_flags;
168	int cltr_flags;
169	int fd;
170	semaphore submit;
171	volatile bool done;
172	struct {
173	struct {
174	__processor_id_t id;
175	void * stack;
176	pthread_t kthrd;
177	volatile bool blocked;
178	} slow;
179	__io_poller_fast fast;
180	__bin_sem_t sem;
181	} poller;
182	};
183
184	//=============================================================================================
185	// I/O Startup / Shutdown logic
186	//=============================================================================================
187	void __kernel_io_startup( cluster & this, unsigned io_flags, bool main_cluster ) {
188	if( (io_flags & CFA_CLUSTER_IO_POLLER_THREAD_SUBMITS) && (io_flags & CFA_CLUSTER_IO_EAGER_SUBMITS) ) {
189	abort("CFA_CLUSTER_IO_POLLER_THREAD_SUBMITS and CFA_CLUSTER_IO_EAGER_SUBMITS cannot be mixed\n");
190	}
191
192	this.io = malloc();
193
194	// Step 1 : call to setup
195	struct io_uring_params params;
196	memset(&params, 0, sizeof(params));
197	if( io_flags & CFA_CLUSTER_IO_KERNEL_POLL_SUBMITS ) params.flags \|= IORING_SETUP_SQPOLL;
198	if( io_flags & CFA_CLUSTER_IO_KERNEL_POLL_COMPLETES ) params.flags \|= IORING_SETUP_IOPOLL;
199
200	uint32_t nentries = entries_per_cluster();
201
202	int fd = syscall(__NR_io_uring_setup, nentries, &params );
203	if(fd < 0) {
204	abort("KERNEL ERROR: IO_URING SETUP - %s\n", strerror(errno));
205	}
206
207	// Step 2 : mmap result
208	memset( this.io, 0, sizeof(struct __io_data) );
209	struct __submition_data & sq = this.io->submit_q;
210	struct __completion_data & cq = this.io->completion_q;
211
212	// calculate the right ring size
213	sq.ring_sz = params.sq_off.array + (params.sq_entries * sizeof(unsigned) );
214	cq.ring_sz = params.cq_off.cqes + (params.cq_entries * sizeof(struct io_uring_cqe));
215
216	// Requires features
217	#if defined(IORING_FEAT_SINGLE_MMAP)
218	// adjust the size according to the parameters
219	if ((params.features & IORING_FEAT_SINGLE_MMAP) != 0) {
220	cq->ring_sz = sq->ring_sz = max(cq->ring_sz, sq->ring_sz);
221	}
222	#endif
223
224	// mmap the Submit Queue into existence
225	sq.ring_ptr = mmap(0, sq.ring_sz, PROT_READ \| PROT_WRITE, MAP_SHARED \| MAP_POPULATE, fd, IORING_OFF_SQ_RING);
226	if (sq.ring_ptr == (void*)MAP_FAILED) {
227	abort("KERNEL ERROR: IO_URING MMAP1 - %s\n", strerror(errno));
228	}
229
230	// Requires features
231	#if defined(IORING_FEAT_SINGLE_MMAP)
232	// mmap the Completion Queue into existence (may or may not be needed)
233	if ((params.features & IORING_FEAT_SINGLE_MMAP) != 0) {
234	cq->ring_ptr = sq->ring_ptr;
235	}
236	else
237	#endif
238	{
239	// We need multiple call to MMAP
240	cq.ring_ptr = mmap(0, cq.ring_sz, PROT_READ \| PROT_WRITE, MAP_SHARED \| MAP_POPULATE, fd, IORING_OFF_CQ_RING);
241	if (cq.ring_ptr == (void*)MAP_FAILED) {
242	munmap(sq.ring_ptr, sq.ring_sz);
243	abort("KERNEL ERROR: IO_URING MMAP2 - %s\n", strerror(errno));
244	}
245	}
246
247	// mmap the submit queue entries
248	size_t size = params.sq_entries * sizeof(struct io_uring_sqe);
249	sq.sqes = (struct io_uring_sqe *)mmap(0, size, PROT_READ \| PROT_WRITE, MAP_SHARED \| MAP_POPULATE, fd, IORING_OFF_SQES);
250	if (sq.sqes == (struct io_uring_sqe *)MAP_FAILED) {
251	munmap(sq.ring_ptr, sq.ring_sz);
252	if (cq.ring_ptr != sq.ring_ptr) munmap(cq.ring_ptr, cq.ring_sz);
253	abort("KERNEL ERROR: IO_URING MMAP3 - %s\n", strerror(errno));
254	}
255
256	// Get the pointers from the kernel to fill the structure
257	// submit queue
258	sq.head = (volatile uint32_t *)(((intptr_t)sq.ring_ptr) + params.sq_off.head);
259	sq.tail = (volatile uint32_t *)(((intptr_t)sq.ring_ptr) + params.sq_off.tail);
260	sq.mask = ( const uint32_t *)(((intptr_t)sq.ring_ptr) + params.sq_off.ring_mask);
261	sq.num = ( const uint32_t *)(((intptr_t)sq.ring_ptr) + params.sq_off.ring_entries);
262	sq.flags = ( uint32_t *)(((intptr_t)sq.ring_ptr) + params.sq_off.flags);
263	sq.dropped = ( uint32_t *)(((intptr_t)sq.ring_ptr) + params.sq_off.dropped);
264	sq.array = ( uint32_t *)(((intptr_t)sq.ring_ptr) + params.sq_off.array);
265	sq.prev_head = *sq.head;
266
267	{
268	const uint32_t num = *sq.num;
269	for( i; num ) {
270	sq.sqes[i].user_data = 0ul64;
271	}
272	}
273
274	(sq.lock){};
275	(sq.release_lock){};
276
277	if( io_flags & ( CFA_CLUSTER_IO_POLLER_THREAD_SUBMITS \| CFA_CLUSTER_IO_EAGER_SUBMITS ) ) {
278	/* paranoid */ verify( is_pow2( io_flags >> CFA_CLUSTER_IO_BUFFLEN_OFFSET ) \|\| ((io_flags >> CFA_CLUSTER_IO_BUFFLEN_OFFSET) < 8) );
279	sq.ready_cnt = max(io_flags >> CFA_CLUSTER_IO_BUFFLEN_OFFSET, 8);
280	sq.ready = alloc_align( 64, sq.ready_cnt );
281	for(i; sq.ready_cnt) {
282	sq.ready[i] = -1ul32;
283	}
284	}
285	else {
286	sq.ready_cnt = 0;
287	sq.ready = 0p;
288	}
289
290	// completion queue
291	cq.head = (volatile uint32_t *)(((intptr_t)cq.ring_ptr) + params.cq_off.head);
292	cq.tail = (volatile uint32_t *)(((intptr_t)cq.ring_ptr) + params.cq_off.tail);
293	cq.mask = ( const uint32_t *)(((intptr_t)cq.ring_ptr) + params.cq_off.ring_mask);
294	cq.num = ( const uint32_t *)(((intptr_t)cq.ring_ptr) + params.cq_off.ring_entries);
295	cq.overflow = ( uint32_t *)(((intptr_t)cq.ring_ptr) + params.cq_off.overflow);
296	cq.cqes = (struct io_uring_cqe *)(((intptr_t)cq.ring_ptr) + params.cq_off.cqes);
297
298	// some paranoid checks
299	/* paranoid / verifyf( (cq.mask) == ((cq.num) - 1ul32), "IO_URING Expected mask to be %u (%u entries), was %u", (cq.num) - 1ul32, cq.num, cq.mask );
300	/* paranoid / verifyf( (cq.num) >= nentries, "IO_URING Expected %u entries, got %u", nentries, *cq.num );
301	/* paranoid / verifyf( (cq.head) == 0, "IO_URING Expected head to be 0, got %u", *cq.head );
302	/* paranoid / verifyf( (cq.tail) == 0, "IO_URING Expected tail to be 0, got %u", *cq.tail );
303
304	/* paranoid / verifyf( (sq.mask) == ((sq.num) - 1ul32), "IO_URING Expected mask to be %u (%u entries), was %u", (sq.num) - 1ul32, sq.num, sq.mask );
305	/* paranoid / verifyf( (sq.num) >= nentries, "IO_URING Expected %u entries, got %u", nentries, *sq.num );
306	/* paranoid / verifyf( (sq.head) == 0, "IO_URING Expected head to be 0, got %u", *sq.head );
307	/* paranoid / verifyf( (sq.tail) == 0, "IO_URING Expected tail to be 0, got %u", *sq.tail );
308
309	// Update the global ring info
310	this.io->ring_flags = params.flags;
311	this.io->cltr_flags = io_flags;
312	this.io->fd = fd;
313	this.io->done = false;
314	(this.io->submit){ min(sq.num, cq.num) };
315
316	if(!main_cluster) {
317	__kernel_io_finish_start( this );
318	}
319	}
320
321	void __kernel_io_finish_start( cluster & this ) {
322	if( this.io->cltr_flags & CFA_CLUSTER_IO_POLLER_USER_THREAD ) {
323	__cfadbg_print_safe(io_core, "Kernel I/O : Creating fast poller for cluter %p\n", &this);
324	(this.io->poller.fast){ this };
325	__thrd_start( this.io->poller.fast, main );
326	}
327
328	// Create the poller thread
329	__cfadbg_print_safe(io_core, "Kernel I/O : Creating slow poller for cluster %p\n", &this);
330	this.io->poller.slow.blocked = false;
331	this.io->poller.slow.stack = __create_pthread( &this.io->poller.slow.kthrd, __io_poller_slow, &this );
332	}
333
334	void __kernel_io_prepare_stop( cluster & this ) {
335	__cfadbg_print_safe(io_core, "Kernel I/O : Stopping pollers for cluster\n", &this);
336	// Notify the poller thread of the shutdown
337	__atomic_store_n(&this.io->done, true, __ATOMIC_SEQ_CST);
338
339	// Stop the IO Poller
340	sigval val = { 1 };
341	pthread_sigqueue( this.io->poller.slow.kthrd, SIGUSR1, val );
342	post( this.io->poller.sem );
343
344	// Wait for the poller thread to finish
345	pthread_join( this.io->poller.slow.kthrd, 0p );
346	free( this.io->poller.slow.stack );
347
348	__cfadbg_print_safe(io_core, "Kernel I/O : Slow poller stopped for cluster\n", &this);
349
350	if( this.io->cltr_flags & CFA_CLUSTER_IO_POLLER_USER_THREAD ) {
351	with( this.io->poller.fast ) {
352	/* paranoid */ verify( this.nprocessors == 0 \|\| &this == mainCluster );
353	/* paranoid */ verify( !ready_mutate_islocked() );
354
355	// We need to adjust the clean-up based on where the thread is
356	if( thrd.state == Ready \|\| thrd.preempted != __NO_PREEMPTION ) {
357
358	ready_schedule_lock( (struct __processor_id_t *)active_processor() );
359
360	// This is the tricky case
361	// The thread was preempted and now it is on the ready queue
362	// The thread should be the last on the list
363	/* paranoid */ verify( thrd.link.next != 0p );
364
365	// Remove the thread from the ready queue of this cluster
366	__attribute__((unused)) bool removed = remove_head( &this, &thrd );
367	/* paranoid */ verify( removed );
368	thrd.link.next = 0p;
369	thrd.link.prev = 0p;
370	__cfaabi_dbg_debug_do( thrd.unpark_stale = true );
371
372	// Fixup the thread state
373	thrd.state = Blocked;
374	thrd.ticket = 0;
375	thrd.preempted = __NO_PREEMPTION;
376
377	ready_schedule_unlock( (struct __processor_id_t *)active_processor() );
378
379	// Pretend like the thread was blocked all along
380	}
381	// !!! This is not an else if !!!
382	if( thrd.state == Blocked ) {
383
384	// This is the "easy case"
385	// The thread is parked and can easily be moved to active cluster
386	verify( thrd.curr_cluster != active_cluster() \|\| thrd.curr_cluster == mainCluster );
387	thrd.curr_cluster = active_cluster();
388
389	// unpark the fast io_poller
390	unpark( &thrd __cfaabi_dbg_ctx2 );
391	}
392	else {
393
394	// The thread is in a weird state
395	// I don't know what to do here
396	abort("Fast poller thread is in unexpected state, cannot clean-up correctly\n");
397	}
398
399	}
400
401	^(this.io->poller.fast){};
402
403	__cfadbg_print_safe(io_core, "Kernel I/O : Fast poller stopped for cluster\n", &this);
404	}
405	}
406
407	void __kernel_io_shutdown( cluster & this, bool main_cluster ) {
408	if(!main_cluster) {
409	__kernel_io_prepare_stop( this );
410	}
411
412	// Shutdown the io rings
413	struct __submition_data & sq = this.io->submit_q;
414	struct __completion_data & cq = this.io->completion_q;
415
416	// unmap the submit queue entries
417	munmap(sq.sqes, (sq.num) sizeof(struct io_uring_sqe));
418
419	// unmap the Submit Queue ring
420	munmap(sq.ring_ptr, sq.ring_sz);
421
422	// unmap the Completion Queue ring, if it is different
423	if (cq.ring_ptr != sq.ring_ptr) {
424	munmap(cq.ring_ptr, cq.ring_sz);
425	}
426
427	// close the file descriptor
428	close(this.io->fd);
429
430	free( this.io->submit_q.ready ); // Maybe null, doesn't matter
431	free( this.io );
432	}
433
434	int __io_uring_enter( struct __io_data & ring, unsigned to_submit, bool get, sigset_t * mask ) {
435	bool need_sys_to_submit = false;
436	bool need_sys_to_complete = false;
437	unsigned min_complete = 0;
438	unsigned flags = 0;
439
440
441	TO_SUBMIT:
442	if( to_submit > 0 ) {
443	if( !(ring.ring_flags & IORING_SETUP_SQPOLL) ) {
444	need_sys_to_submit = true;
445	break TO_SUBMIT;
446	}
447	if( (*ring.submit_q.flags) & IORING_SQ_NEED_WAKEUP ) {
448	need_sys_to_submit = true;
449	flags \|= IORING_ENTER_SQ_WAKEUP;
450	}
451	}
452
453	TO_COMPLETE:
454	if( get && !(ring.ring_flags & IORING_SETUP_SQPOLL) ) {
455	flags \|= IORING_ENTER_GETEVENTS;
456	if( mask ) {
457	need_sys_to_complete = true;
458	min_complete = 1;
459	break TO_COMPLETE;
460	}
461	if( (ring.ring_flags & IORING_SETUP_IOPOLL) ) {
462	need_sys_to_complete = true;
463	}
464	}
465
466	int ret = 0;
467	if( need_sys_to_submit \|\| need_sys_to_complete ) {
468	ret = syscall( __NR_io_uring_enter, ring.fd, to_submit, min_complete, flags, mask, _NSIG / 8);
469	if( ret < 0 ) {
470	switch((int)errno) {
471	case EAGAIN:
472	case EINTR:
473	ret = -1;
474	break;
475	default:
476	abort( "KERNEL ERROR: IO_URING SYSCALL - (%d) %s\n", (int)errno, strerror(errno) );
477	}
478	}
479	}
480
481	// Memory barrier
482	__atomic_thread_fence( __ATOMIC_SEQ_CST );
483	return ret;
484	}
485
486	//=============================================================================================
487	// I/O Polling
488	//=============================================================================================
489	static unsigned __collect_submitions( struct __io_data & ring );
490	static uint32_t __release_consumed_submission( struct __io_data & ring );
491
492	// Process a single completion message from the io_uring
493	// This is NOT thread-safe
494	static [int, bool] __drain_io( & struct __io_data ring, * sigset_t mask ) {
495	/* paranoid */ verify( !kernelTLS.preemption_state.enabled );
496	const uint32_t smask = *ring.submit_q.mask;
497
498	unsigned to_submit = 0;
499	if( ring.cltr_flags & CFA_CLUSTER_IO_POLLER_THREAD_SUBMITS ) {
500	// If the poller thread also submits, then we need to aggregate the submissions which are ready
501	to_submit = __collect_submitions( ring );
502	}
503
504	int ret = __io_uring_enter(ring, to_submit, true, mask);
505	if( ret < 0 ) {
506	return [0, true];
507	}
508
509	// update statistics
510	if (to_submit > 0) {
511	__STATS__( true,
512	if( to_submit > 0 ) {
513	io.submit_q.submit_avg.rdy += to_submit;
514	io.submit_q.submit_avg.csm += ret;
515	io.submit_q.submit_avg.cnt += 1;
516	}
517	)
518	}
519
520	// Release the consumed SQEs
521	__release_consumed_submission( ring );
522
523	// Drain the queue
524	unsigned head = *ring.completion_q.head;
525	unsigned tail = *ring.completion_q.tail;
526	const uint32_t mask = *ring.completion_q.mask;
527
528	// Nothing was new return 0
529	if (head == tail) {
530	return [0, to_submit > 0];
531	}
532
533	uint32_t count = tail - head;
534	/* paranoid */ verify( count != 0 );
535	for(i; count) {
536	unsigned idx = (head + i) & mask;
537	struct io_uring_cqe & cqe = ring.completion_q.cqes[idx];
538
539	/* paranoid */ verify(&cqe);
540
541	struct __io_user_data_t * data = (struct __io_user_data_t *)(uintptr_t)cqe.user_data;
542	__cfadbg_print_safe( io, "Kernel I/O : Performed reading io cqe %p, result %d for %p\n", data, cqe.res, data->thrd );
543
544	data->result = cqe.res;
545	if(!mask) { unpark( data->thrd __cfaabi_dbg_ctx2 ); }
546	else { __unpark( &ring.poller.slow.id, data->thrd __cfaabi_dbg_ctx2 ); }
547	}
548
549	// Allow new submissions to happen
550	// V(ring.submit, count);
551
552	// Mark to the kernel that the cqe has been seen
553	// Ensure that the kernel only sees the new value of the head index after the CQEs have been read.
554	__atomic_thread_fence( __ATOMIC_SEQ_CST );
555	__atomic_fetch_add( ring.completion_q.head, count, __ATOMIC_RELAXED );
556
557	return [count, count > 0 \|\| to_submit > 0];
558	}
559
560	static void * __io_poller_slow( void * arg ) {
561	#if !defined( __CFA_NO_STATISTICS__ )
562	__stats_t local_stats;
563	__init_stats( &local_stats );
564	kernelTLS.this_stats = &local_stats;
565	#endif
566
567	cluster * cltr = (cluster *)arg;
568	struct __io_data & ring = *cltr->io;
569
570	ring.poller.slow.id.id = doregister( &ring.poller.slow.id );
571
572	sigset_t mask;
573	sigfillset(&mask);
574	if ( pthread_sigmask( SIG_BLOCK, &mask, 0p ) == -1 ) {
575	abort( "KERNEL ERROR: IO_URING - pthread_sigmask" );
576	}
577
578	sigdelset( &mask, SIGUSR1 );
579
580	verify( (ring.submit_q.head) == (ring.submit_q.tail) );
581	verify( (ring.completion_q.head) == (ring.completion_q.tail) );
582
583	__cfadbg_print_safe(io_core, "Kernel I/O : Slow poller for ring %p ready\n", &ring);
584
585	if( ring.cltr_flags & CFA_CLUSTER_IO_POLLER_USER_THREAD ) {
586	while(!__atomic_load_n(&ring.done, __ATOMIC_SEQ_CST)) {
587
588	__atomic_store_n( &ring.poller.slow.blocked, true, __ATOMIC_SEQ_CST );
589
590	// In the user-thread approach drain and if anything was drained,
591	// batton pass to the user-thread
592	int count;
593	bool again;
594	[count, again] = __drain_io( ring, &mask );
595
596	__atomic_store_n( &ring.poller.slow.blocked, false, __ATOMIC_SEQ_CST );
597
598	// Update statistics
599	__STATS__( true,
600	io.complete_q.completed_avg.val += count;
601	io.complete_q.completed_avg.slow_cnt += 1;
602	)
603
604	if(again) {
605	__cfadbg_print_safe(io_core, "Kernel I/O : Moving to ring %p to fast poller\n", &ring);
606	__unpark( &ring.poller.slow.id, &ring.poller.fast.thrd __cfaabi_dbg_ctx2 );
607	wait( ring.poller.sem );
608	}
609	}
610	}
611	else {
612	while(!__atomic_load_n(&ring.done, __ATOMIC_SEQ_CST)) {
613	//In the naive approach, just poll the io completion queue directly
614	int count;
615	bool again;
616	[count, again] = __drain_io( ring, &mask );
617
618	// Update statistics
619	__STATS__( true,
620	io.complete_q.completed_avg.val += count;
621	io.complete_q.completed_avg.slow_cnt += 1;
622	)
623	}
624	}
625
626	__cfadbg_print_safe(io_core, "Kernel I/O : Slow poller for ring %p stopping\n", &ring);
627
628	unregister( &ring.poller.slow.id );
629
630	#if !defined(__CFA_NO_STATISTICS__)
631	__tally_stats(cltr->stats, &local_stats);
632	#endif
633
634	return 0p;
635	}
636
637	void main( __io_poller_fast & this ) {
638	verify( this.ring->cltr_flags & CFA_CLUSTER_IO_POLLER_USER_THREAD );
639
640	// Start parked
641	park( __cfaabi_dbg_ctx );
642
643	__cfadbg_print_safe(io_core, "Kernel I/O : Fast poller for ring %p ready\n", &this.ring);
644
645	int reset = 0;
646
647	// Then loop until we need to start
648	while(!__atomic_load_n(&this.ring->done, __ATOMIC_SEQ_CST)) {
649
650	// Drain the io
651	int count;
652	bool again;
653	disable_interrupts();
654	[count, again] = __drain_io( *this.ring, 0p );
655
656	if(!again) reset++;
657
658	// Update statistics
659	__STATS__( true,
660	io.complete_q.completed_avg.val += count;
661	io.complete_q.completed_avg.fast_cnt += 1;
662	)
663	enable_interrupts( __cfaabi_dbg_ctx );
664
665	// If we got something, just yield and check again
666	if(reset < 5) {
667	yield();
668	}
669	// We didn't get anything baton pass to the slow poller
670	else {
671	__cfadbg_print_safe(io_core, "Kernel I/O : Moving to ring %p to slow poller\n", &this.ring);
672	reset = 0;
673
674	// wake up the slow poller
675	post( this.ring->poller.sem );
676
677	// park this thread
678	park( __cfaabi_dbg_ctx );
679	}
680	}
681
682	__cfadbg_print_safe(io_core, "Kernel I/O : Fast poller for ring %p stopping\n", &this.ring);
683	}
684
685	static inline void __wake_poller( struct __io_data & ring ) __attribute__((artificial));
686	static inline void __wake_poller( struct __io_data & ring ) {
687	if(!__atomic_load_n( &ring.poller.slow.blocked, __ATOMIC_SEQ_CST)) return;
688
689	sigval val = { 1 };
690	pthread_sigqueue( ring.poller.slow.kthrd, SIGUSR1, val );
691	}
692
693	//=============================================================================================
694	// I/O Submissions
695	//=============================================================================================
696
697	// Submition steps :
698	// 1 - Allocate a queue entry. The ring already has memory for all entries but only the ones
699	// listed in sq.array are visible by the kernel. For those not listed, the kernel does not
700	// offer any assurance that an entry is not being filled by multiple flags. Therefore, we
701	// need to write an allocator that allows allocating concurrently.
702	//
703	// 2 - Actually fill the submit entry, this is the only simple and straightforward step.
704	//
705	// 3 - Append the entry index to the array and adjust the tail accordingly. This operation
706	// needs to arrive to two concensus at the same time:
707	// A - The order in which entries are listed in the array: no two threads must pick the
708	// same index for their entries
709	// B - When can the tail be update for the kernel. EVERY entries in the array between
710	// head and tail must be fully filled and shouldn't ever be touched again.
711	//
712
713	[* struct io_uring_sqe, uint32_t] __submit_alloc( struct __io_data & ring, uint64_t data ) {
714	/* paranoid */ verify( data != 0 );
715
716	// Prepare the data we need
717	__attribute((unused)) int len = 0;
718	__attribute((unused)) int block = 0;
719	uint32_t cnt = *ring.submit_q.num;
720	uint32_t mask = *ring.submit_q.mask;
721
722	disable_interrupts();
723	uint32_t off = __tls_rand();
724	enable_interrupts( __cfaabi_dbg_ctx );
725
726	// Loop around looking for an available spot
727	for() {
728	// Look through the list starting at some offset
729	for(i; cnt) {
730	uint64_t expected = 0;
731	uint32_t idx = (i + off) & mask;
732	struct io_uring_sqe * sqe = &ring.submit_q.sqes[idx];
733	volatile uint64_t * udata = &sqe->user_data;
734
735	if( *udata == expected &&
736	__atomic_compare_exchange_n( udata, &expected, data, true, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED ) )
737	{
738	// update statistics
739	__STATS__( false,
740	io.submit_q.alloc_avg.val += len;
741	io.submit_q.alloc_avg.block += block;
742	io.submit_q.alloc_avg.cnt += 1;
743	)
744
745
746	// Success return the data
747	return [sqe, idx];
748	}
749	verify(expected != data);
750
751	len ++;
752	}
753
754	block++;
755	yield();
756	}
757	}
758
759	static inline uint32_t __submit_to_ready_array( struct __io_data & ring, uint32_t idx, const uint32_t mask ) {
760	/* paranoid */ verify( idx <= mask );
761	/* paranoid */ verify( idx != -1ul32 );
762
763	// We need to find a spot in the ready array
764	__attribute((unused)) int len = 0;
765	__attribute((unused)) int block = 0;
766	uint32_t ready_mask = ring.submit_q.ready_cnt - 1;
767
768	disable_interrupts();
769	uint32_t off = __tls_rand();
770	enable_interrupts( __cfaabi_dbg_ctx );
771
772	uint32_t picked;
773	LOOKING: for() {
774	for(i; ring.submit_q.ready_cnt) {
775	picked = (i + off) & ready_mask;
776	uint32_t expected = -1ul32;
777	if( __atomic_compare_exchange_n( &ring.submit_q.ready[picked], &expected, idx, true, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED ) ) {
778	break LOOKING;
779	}
780	verify(expected != idx);
781
782	len ++;
783	}
784
785	block++;
786	if( try_lock(ring.submit_q.lock __cfaabi_dbg_ctx2) ) {
787	__release_consumed_submission( ring );
788	unlock( ring.submit_q.lock );
789	}
790	else {
791	yield();
792	}
793	}
794
795	// update statistics
796	__STATS__( false,
797	io.submit_q.look_avg.val += len;
798	io.submit_q.look_avg.block += block;
799	io.submit_q.look_avg.cnt += 1;
800	)
801
802	return picked;
803	}
804
805	void __submit( struct __io_data & ring, uint32_t idx ) {
806	// Get now the data we definetely need
807	uint32_t * const tail = ring.submit_q.tail;
808	const uint32_t mask = *ring.submit_q.mask;
809
810	// There are 2 submission schemes, check which one we are using
811	if( ring.cltr_flags & CFA_CLUSTER_IO_POLLER_THREAD_SUBMITS ) {
812	// If the poller thread submits, then we just need to add this to the ready array
813	__submit_to_ready_array( ring, idx, mask );
814
815	__wake_poller( ring );
816
817	__cfadbg_print_safe( io, "Kernel I/O : Added %u to ready for %p\n", idx, active_thread() );
818	}
819	else if( ring.cltr_flags & CFA_CLUSTER_IO_EAGER_SUBMITS ) {
820	uint32_t picked = __submit_to_ready_array( ring, idx, mask );
821
822	for() {
823	yield();
824
825	// If some one else collected our index, we are done
826	#warning ABA problem
827	if( ring.submit_q.ready[picked] != idx ) {
828	__STATS__( false,
829	io.submit_q.helped += 1;
830	)
831	return;
832	}
833
834	if( try_lock(ring.submit_q.lock __cfaabi_dbg_ctx2) ) {
835	__STATS__( false,
836	io.submit_q.leader += 1;
837	)
838	break;
839	}
840
841	__STATS__( false,
842	io.submit_q.busy += 1;
843	)
844	}
845
846	// We got the lock
847	unsigned to_submit = __collect_submitions( ring );
848	int ret = __io_uring_enter( ring, to_submit, false, 0p );
849	if( ret < 0 ) {
850	unlock(ring.submit_q.lock);
851	return;
852	}
853
854	/* paranoid */ verify( ret > 0 \|\| (ring.ring_flags & IORING_SETUP_SQPOLL) );
855
856	// Release the consumed SQEs
857	__release_consumed_submission( ring );
858
859	// update statistics
860	__STATS__( true,
861	io.submit_q.submit_avg.rdy += to_submit;
862	io.submit_q.submit_avg.csm += ret;
863	io.submit_q.submit_avg.cnt += 1;
864	)
865
866	unlock(ring.submit_q.lock);
867	}
868	else {
869	// get mutual exclusion
870	lock(ring.submit_q.lock __cfaabi_dbg_ctx2);
871
872	/* paranoid */ verifyf( ring.submit_q.sqes[ idx ].user_data != 0,
873	/* paranoid */ "index %u already reclaimed\n"
874	/* paranoid */ "head %u, prev %u, tail %u\n"
875	/* paranoid */ "[-0: %u,-1: %u,-2: %u,-3: %u]\n",
876	/* paranoid */ idx,
877	/* paranoid / ring.submit_q.head, ring.submit_q.prev_head, *tail
878	/* paranoid / ,ring.submit_q.array[ ((ring.submit_q.head) - 0) & (*ring.submit_q.mask) ]
879	/* paranoid / ,ring.submit_q.array[ ((ring.submit_q.head) - 1) & (*ring.submit_q.mask) ]
880	/* paranoid / ,ring.submit_q.array[ ((ring.submit_q.head) - 2) & (*ring.submit_q.mask) ]
881	/* paranoid / ,ring.submit_q.array[ ((ring.submit_q.head) - 3) & (*ring.submit_q.mask) ]
882	/* paranoid */ );
883
884	// Append to the list of ready entries
885
886	/* paranoid */ verify( idx <= mask );
887	ring.submit_q.array[ (*tail) & mask ] = idx;
888	__atomic_fetch_add(tail, 1ul32, __ATOMIC_SEQ_CST);
889
890	// Submit however, many entries need to be submitted
891	int ret = __io_uring_enter( ring, 1, false, 0p );
892	if( ret < 0 ) {
893	switch((int)errno) {
894	default:
895	abort( "KERNEL ERROR: IO_URING SUBMIT - %s\n", strerror(errno) );
896	}
897	}
898
899	// update statistics
900	__STATS__( false,
901	io.submit_q.submit_avg.csm += 1;
902	io.submit_q.submit_avg.cnt += 1;
903	)
904
905	// Release the consumed SQEs
906	__release_consumed_submission( ring );
907
908	unlock(ring.submit_q.lock);
909
910	__cfadbg_print_safe( io, "Kernel I/O : Performed io_submit for %p, returned %d\n", active_thread(), ret );
911	}
912	}
913
914	static unsigned __collect_submitions( struct __io_data & ring ) {
915	/* paranoid */ verify( ring.submit_q.ready != 0p );
916	/* paranoid */ verify( ring.submit_q.ready_cnt > 0 );
917
918	unsigned to_submit = 0;
919	uint32_t tail = *ring.submit_q.tail;
920	const uint32_t mask = *ring.submit_q.mask;
921
922	// Go through the list of ready submissions
923	for( i; ring.submit_q.ready_cnt ) {
924	// replace any submission with the sentinel, to consume it.
925	uint32_t idx = __atomic_exchange_n( &ring.submit_q.ready[i], -1ul32, __ATOMIC_RELAXED);
926
927	// If it was already the sentinel, then we are done
928	if( idx == -1ul32 ) continue;
929
930	// If we got a real submission, append it to the list
931	ring.submit_q.array[ (tail + to_submit) & mask ] = idx & mask;
932	to_submit++;
933	}
934
935	// Increment the tail based on how many we are ready to submit
936	__atomic_fetch_add(ring.submit_q.tail, to_submit, __ATOMIC_SEQ_CST);
937
938	return to_submit;
939	}
940
941	static uint32_t __release_consumed_submission( struct __io_data & ring ) {
942	const uint32_t smask = *ring.submit_q.mask;
943
944	if( !try_lock(ring.submit_q.release_lock __cfaabi_dbg_ctx2) ) return 0;
945	uint32_t chead = *ring.submit_q.head;
946	uint32_t phead = ring.submit_q.prev_head;
947	ring.submit_q.prev_head = chead;
948	unlock(ring.submit_q.release_lock);
949
950	uint32_t count = chead - phead;
951	for( i; count ) {
952	uint32_t idx = ring.submit_q.array[ (phead + i) & smask ];
953	ring.submit_q.sqes[ idx ].user_data = 0;
954	}
955	return count;
956	}
957
958	//=============================================================================================
959	// I/O Submissions
960	//=============================================================================================
961
962	void register_fixed_files( cluster & cl, int * files, unsigned count ) {
963	int ret = syscall( __NR_io_uring_register, cl.io->fd, IORING_REGISTER_FILES, files, count );
964	if( ret < 0 ) {
965	abort( "KERNEL ERROR: IO_URING SYSCALL - (%d) %s\n", (int)errno, strerror(errno) );
966	}
967
968	__cfadbg_print_safe( io_core, "Kernel I/O : Performed io_register for %p, returned %d\n", active_thread(), ret );
969	}
970	#endif

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