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io.cfa @ 4ec028d

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

Last change on this file since 4ec028d was 4ec028d, checked in by Thierry Delisle <tdelisle@…>, 4 years ago
Merge branch 'master' of plg.uwaterloo.ca:software/cfa/cfa-cc
Property mode set to `100644`
File size: 26.1 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 __CFA_DEBUG_PRINT_IO__
17	// #define __CFA_DEBUG_PRINT_IO_CORE__
18
19	#include "kernel.hfa"
20	#include "bitmanip.hfa"
21
22	#if !defined(HAVE_LINUX_IO_URING_H)
23	void __kernel_io_startup( cluster &, unsigned, bool ) {
24	// Nothing to do without io_uring
25	}
26
27	void __kernel_io_finish_start( cluster & ) {
28	// Nothing to do without io_uring
29	}
30
31	void __kernel_io_prepare_stop( cluster & ) {
32	// Nothing to do without io_uring
33	}
34
35	void __kernel_io_shutdown( cluster &, bool ) {
36	// Nothing to do without io_uring
37	}
38
39	#else
40	#define _GNU_SOURCE /* See feature_test_macros(7) */
41	#include <errno.h>
42	#include <stdint.h>
43	#include <string.h>
44	#include <unistd.h>
45	#include <sys/mman.h>
46
47	extern "C" {
48	#include <sys/syscall.h>
49
50	#include <linux/io_uring.h>
51	}
52
53	#include "bits/signal.hfa"
54	#include "kernel_private.hfa"
55	#include "thread.hfa"
56
57	uint32_t entries_per_cluster() {
58	return 256;
59	}
60
61	static void * __io_poller_slow( void * arg );
62
63	// Weirdly, some systems that do support io_uring don't actually define these
64	#ifdef __alpha__
65	/*
66	* alpha is the only exception, all other architectures
67	* have common numbers for new system calls.
68	*/
69	#ifndef __NR_io_uring_setup
70	#define __NR_io_uring_setup 535
71	#endif
72	#ifndef __NR_io_uring_enter
73	#define __NR_io_uring_enter 536
74	#endif
75	#ifndef __NR_io_uring_register
76	#define __NR_io_uring_register 537
77	#endif
78	#else /* !__alpha__ */
79	#ifndef __NR_io_uring_setup
80	#define __NR_io_uring_setup 425
81	#endif
82	#ifndef __NR_io_uring_enter
83	#define __NR_io_uring_enter 426
84	#endif
85	#ifndef __NR_io_uring_register
86	#define __NR_io_uring_register 427
87	#endif
88	#endif
89
90	// Fast poller user-thread
91	// Not using the "thread" keyword because we want to control
92	// more carefully when to start/stop it
93	struct __io_poller_fast {
94	struct __io_data * ring;
95	$thread thrd;
96	};
97
98	void ?{}( __io_poller_fast & this, struct cluster & cltr ) {
99	this.ring = cltr.io;
100	(this.thrd){ "Fast I/O Poller", cltr };
101	}
102	void ^?{}( __io_poller_fast & mutex this );
103	void main( __io_poller_fast & this );
104	static inline $thread * get_thread( __io_poller_fast & this ) { return &this.thrd; }
105	void ^?{}( __io_poller_fast & mutex this ) {}
106
107	struct __submition_data {
108	// Head and tail of the ring (associated with array)
109	volatile uint32_t * head;
110	volatile uint32_t * tail;
111
112	// The actual kernel ring which uses head/tail
113	// indexes into the sqes arrays
114	uint32_t * array;
115
116	// number of entries and mask to go with it
117	const uint32_t * num;
118	const uint32_t * mask;
119
120	// Submission flags (Not sure what for)
121	uint32_t * flags;
122
123	// number of sqes not submitted (whatever that means)
124	uint32_t * dropped;
125
126	// Like head/tail but not seen by the kernel
127	volatile uint32_t * ready;
128	uint32_t ready_cnt;
129
130	__spinlock_t lock;
131
132	// A buffer of sqes (not the actual ring)
133	struct io_uring_sqe * sqes;
134
135	// The location and size of the mmaped area
136	void * ring_ptr;
137	size_t ring_sz;
138	};
139
140	struct __completion_data {
141	// Head and tail of the ring
142	volatile uint32_t * head;
143	volatile uint32_t * tail;
144
145	// number of entries and mask to go with it
146	const uint32_t * mask;
147	const uint32_t * num;
148
149	// number of cqes not submitted (whatever that means)
150	uint32_t * overflow;
151
152	// the kernel ring
153	struct io_uring_cqe * cqes;
154
155	// The location and size of the mmaped area
156	void * ring_ptr;
157	size_t ring_sz;
158	};
159
160	struct __io_data {
161	struct __submition_data submit_q;
162	struct __completion_data completion_q;
163	uint32_t ring_flags;
164	int cltr_flags;
165	int fd;
166	semaphore submit;
167	volatile bool done;
168	struct {
169	struct {
170	__processor_id_t id;
171	void * stack;
172	pthread_t kthrd;
173	volatile bool blocked;
174	} slow;
175	__io_poller_fast fast;
176	__bin_sem_t sem;
177	} poller;
178	};
179
180	//=============================================================================================
181	// I/O Startup / Shutdown logic
182	//=============================================================================================
183	void __kernel_io_startup( cluster & this, unsigned io_flags, bool main_cluster ) {
184	this.io = malloc();
185
186	// Step 1 : call to setup
187	struct io_uring_params params;
188	memset(&params, 0, sizeof(params));
189
190	uint32_t nentries = entries_per_cluster();
191
192	int fd = syscall(__NR_io_uring_setup, nentries, &params );
193	if(fd < 0) {
194	abort("KERNEL ERROR: IO_URING SETUP - %s\n", strerror(errno));
195	}
196
197	// Step 2 : mmap result
198	memset( this.io, 0, sizeof(struct __io_data) );
199	struct __submition_data & sq = this.io->submit_q;
200	struct __completion_data & cq = this.io->completion_q;
201
202	// calculate the right ring size
203	sq.ring_sz = params.sq_off.array + (params.sq_entries * sizeof(unsigned) );
204	cq.ring_sz = params.cq_off.cqes + (params.cq_entries * sizeof(struct io_uring_cqe));
205
206	// Requires features
207	#if defined(IORING_FEAT_SINGLE_MMAP)
208	// adjust the size according to the parameters
209	if ((params.features & IORING_FEAT_SINGLE_MMAP) != 0) {
210	cq->ring_sz = sq->ring_sz = max(cq->ring_sz, sq->ring_sz);
211	}
212	#endif
213
214	// mmap the Submit Queue into existence
215	sq.ring_ptr = mmap(0, sq.ring_sz, PROT_READ \| PROT_WRITE, MAP_SHARED \| MAP_POPULATE, fd, IORING_OFF_SQ_RING);
216	if (sq.ring_ptr == (void*)MAP_FAILED) {
217	abort("KERNEL ERROR: IO_URING MMAP1 - %s\n", strerror(errno));
218	}
219
220	// Requires features
221	#if defined(IORING_FEAT_SINGLE_MMAP)
222	// mmap the Completion Queue into existence (may or may not be needed)
223	if ((params.features & IORING_FEAT_SINGLE_MMAP) != 0) {
224	cq->ring_ptr = sq->ring_ptr;
225	}
226	else
227	#endif
228	{
229	// We need multiple call to MMAP
230	cq.ring_ptr = mmap(0, cq.ring_sz, PROT_READ \| PROT_WRITE, MAP_SHARED \| MAP_POPULATE, fd, IORING_OFF_CQ_RING);
231	if (cq.ring_ptr == (void*)MAP_FAILED) {
232	munmap(sq.ring_ptr, sq.ring_sz);
233	abort("KERNEL ERROR: IO_URING MMAP2 - %s\n", strerror(errno));
234	}
235	}
236
237	// mmap the submit queue entries
238	size_t size = params.sq_entries * sizeof(struct io_uring_sqe);
239	sq.sqes = (struct io_uring_sqe *)mmap(0, size, PROT_READ \| PROT_WRITE, MAP_SHARED \| MAP_POPULATE, fd, IORING_OFF_SQES);
240	if (sq.sqes == (struct io_uring_sqe *)MAP_FAILED) {
241	munmap(sq.ring_ptr, sq.ring_sz);
242	if (cq.ring_ptr != sq.ring_ptr) munmap(cq.ring_ptr, cq.ring_sz);
243	abort("KERNEL ERROR: IO_URING MMAP3 - %s\n", strerror(errno));
244	}
245
246	// Get the pointers from the kernel to fill the structure
247	// submit queue
248	sq.head = (volatile uint32_t *)(((intptr_t)sq.ring_ptr) + params.sq_off.head);
249	sq.tail = (volatile uint32_t *)(((intptr_t)sq.ring_ptr) + params.sq_off.tail);
250	sq.mask = ( const uint32_t *)(((intptr_t)sq.ring_ptr) + params.sq_off.ring_mask);
251	sq.num = ( const uint32_t *)(((intptr_t)sq.ring_ptr) + params.sq_off.ring_entries);
252	sq.flags = ( uint32_t *)(((intptr_t)sq.ring_ptr) + params.sq_off.flags);
253	sq.dropped = ( uint32_t *)(((intptr_t)sq.ring_ptr) + params.sq_off.dropped);
254	sq.array = ( uint32_t *)(((intptr_t)sq.ring_ptr) + params.sq_off.array);
255
256	{
257	const uint32_t num = *sq.num;
258	for( i; num ) {
259	sq.sqes[i].user_data = 0ul64;
260	}
261	}
262
263	if( io_flags & CFA_CLUSTER_IO_POLLER_THREAD_SUBMITS ) {
264	/* paranoid */ verify( is_pow2( io_flags >> CFA_CLUSTER_IO_BUFFLEN_OFFSET ) \|\| ((io_flags >> CFA_CLUSTER_IO_BUFFLEN_OFFSET) < 8) );
265	sq.ready_cnt = max(io_flags >> CFA_CLUSTER_IO_BUFFLEN_OFFSET, 8);
266	sq.ready = alloc_align( 64, sq.ready_cnt );
267	for(i; sq.ready_cnt) {
268	sq.ready[i] = -1ul32;
269	}
270	}
271	else {
272	sq.ready_cnt = 0;
273	sq.ready = 0p;
274	}
275
276	// completion queue
277	cq.head = (volatile uint32_t *)(((intptr_t)cq.ring_ptr) + params.cq_off.head);
278	cq.tail = (volatile uint32_t *)(((intptr_t)cq.ring_ptr) + params.cq_off.tail);
279	cq.mask = ( const uint32_t *)(((intptr_t)cq.ring_ptr) + params.cq_off.ring_mask);
280	cq.num = ( const uint32_t *)(((intptr_t)cq.ring_ptr) + params.cq_off.ring_entries);
281	cq.overflow = ( uint32_t *)(((intptr_t)cq.ring_ptr) + params.cq_off.overflow);
282	cq.cqes = (struct io_uring_cqe *)(((intptr_t)cq.ring_ptr) + params.cq_off.cqes);
283
284	// some paranoid checks
285	/* 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 );
286	/* paranoid / verifyf( (cq.num) >= nentries, "IO_URING Expected %u entries, got %u", nentries, *cq.num );
287	/* paranoid / verifyf( (cq.head) == 0, "IO_URING Expected head to be 0, got %u", *cq.head );
288	/* paranoid / verifyf( (cq.tail) == 0, "IO_URING Expected tail to be 0, got %u", *cq.tail );
289
290	/* 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 );
291	/* paranoid / verifyf( (sq.num) >= nentries, "IO_URING Expected %u entries, got %u", nentries, *sq.num );
292	/* paranoid / verifyf( (sq.head) == 0, "IO_URING Expected head to be 0, got %u", *sq.head );
293	/* paranoid / verifyf( (sq.tail) == 0, "IO_URING Expected tail to be 0, got %u", *sq.tail );
294
295	// Update the global ring info
296	this.io->ring_flags = params.flags;
297	this.io->cltr_flags = io_flags;
298	this.io->fd = fd;
299	this.io->done = false;
300	(this.io->submit){ min(sq.num, cq.num) };
301
302	if(!main_cluster) {
303	__kernel_io_finish_start( this );
304	}
305	}
306
307	void __kernel_io_finish_start( cluster & this ) {
308	if( this.io->cltr_flags & CFA_CLUSTER_IO_POLLER_USER_THREAD ) {
309	__cfadbg_print_safe(io_core, "Kernel I/O : Creating fast poller for cluter %p\n", &this);
310	(this.io->poller.fast){ this };
311	__thrd_start( this.io->poller.fast, main );
312	}
313
314	// Create the poller thread
315	__cfadbg_print_safe(io_core, "Kernel I/O : Creating slow poller for cluter %p\n", &this);
316	this.io->poller.slow.blocked = false;
317	this.io->poller.slow.stack = __create_pthread( &this.io->poller.slow.kthrd, __io_poller_slow, &this );
318	}
319
320	void __kernel_io_prepare_stop( cluster & this ) {
321	__cfadbg_print_safe(io_core, "Kernel I/O : Stopping pollers for cluster\n", &this);
322	// Notify the poller thread of the shutdown
323	__atomic_store_n(&this.io->done, true, __ATOMIC_SEQ_CST);
324
325	// Stop the IO Poller
326	sigval val = { 1 };
327	pthread_sigqueue( this.io->poller.slow.kthrd, SIGUSR1, val );
328	post( this.io->poller.sem );
329
330	// Wait for the poller thread to finish
331	pthread_join( this.io->poller.slow.kthrd, 0p );
332	free( this.io->poller.slow.stack );
333
334	__cfadbg_print_safe(io_core, "Kernel I/O : Slow poller stopped for cluster\n", &this);
335
336	if( this.io->cltr_flags & CFA_CLUSTER_IO_POLLER_USER_THREAD ) {
337	with( this.io->poller.fast ) {
338	/* paranoid */ verify( this.nprocessors == 0 \|\| &this == mainCluster );
339	/* paranoid */ verify( !ready_mutate_islocked() );
340
341	// We need to adjust the clean-up based on where the thread is
342	if( thrd.state == Ready \|\| thrd.preempted != __NO_PREEMPTION ) {
343
344	ready_schedule_lock( (struct __processor_id_t *)active_processor() );
345
346	// This is the tricky case
347	// The thread was preempted and now it is on the ready queue
348	// The thread should be the last on the list
349	/* paranoid */ verify( thrd.link.next != 0p );
350
351	// Remove the thread from the ready queue of this cluster
352	__attribute__((unused)) bool removed = remove_head( &this, &thrd );
353	/* paranoid */ verify( removed );
354	thrd.link.next = 0p;
355	thrd.link.prev = 0p;
356	__cfaabi_dbg_debug_do( thrd.unpark_stale = true );
357
358	// Fixup the thread state
359	thrd.state = Blocked;
360	thrd.ticket = 0;
361	thrd.preempted = __NO_PREEMPTION;
362
363	ready_schedule_unlock( (struct __processor_id_t *)active_processor() );
364
365	// Pretend like the thread was blocked all along
366	}
367	// !!! This is not an else if !!!
368	if( thrd.state == Blocked ) {
369
370	// This is the "easy case"
371	// The thread is parked and can easily be moved to active cluster
372	verify( thrd.curr_cluster != active_cluster() \|\| thrd.curr_cluster == mainCluster );
373	thrd.curr_cluster = active_cluster();
374
375	// unpark the fast io_poller
376	unpark( &thrd __cfaabi_dbg_ctx2 );
377	}
378	else {
379
380	// The thread is in a weird state
381	// I don't know what to do here
382	abort("Fast poller thread is in unexpected state, cannot clean-up correctly\n");
383	}
384
385	}
386
387	^(this.io->poller.fast){};
388
389	__cfadbg_print_safe(io_core, "Kernel I/O : Fast poller stopped for cluster\n", &this);
390	}
391	}
392
393	void __kernel_io_shutdown( cluster & this, bool main_cluster ) {
394	if(!main_cluster) {
395	__kernel_io_prepare_stop( this );
396	}
397
398	// Shutdown the io rings
399	struct __submition_data & sq = this.io->submit_q;
400	struct __completion_data & cq = this.io->completion_q;
401
402	// unmap the submit queue entries
403	munmap(sq.sqes, (sq.num) sizeof(struct io_uring_sqe));
404
405	// unmap the Submit Queue ring
406	munmap(sq.ring_ptr, sq.ring_sz);
407
408	// unmap the Completion Queue ring, if it is different
409	if (cq.ring_ptr != sq.ring_ptr) {
410	munmap(cq.ring_ptr, cq.ring_sz);
411	}
412
413	// close the file descriptor
414	close(this.io->fd);
415
416	free( this.io->submit_q.ready ); // Maybe null, doesn't matter
417	free( this.io );
418	}
419
420	//=============================================================================================
421	// I/O Polling
422	//=============================================================================================
423	// Process a single completion message from the io_uring
424	// This is NOT thread-safe
425	static [int, bool] __drain_io( & struct __io_data ring, * sigset_t mask, int waitcnt, bool in_kernel ) {
426	unsigned to_submit = 0;
427	if( ring.cltr_flags & CFA_CLUSTER_IO_POLLER_THREAD_SUBMITS ) {
428
429	// If the poller thread also submits, then we need to aggregate the submissions which are ready
430	uint32_t tail = *ring.submit_q.tail;
431	const uint32_t mask = *ring.submit_q.mask;
432
433	// Go through the list of ready submissions
434	for( i; ring.submit_q.ready_cnt ) {
435	// replace any submission with the sentinel, to consume it.
436	uint32_t idx = __atomic_exchange_n( &ring.submit_q.ready[i], -1ul32, __ATOMIC_RELAXED);
437
438	// If it was already the sentinel, then we are done
439	if( idx == -1ul32 ) continue;
440
441	// If we got a real submission, append it to the list
442	ring.submit_q.array[ (tail + to_submit) & mask ] = idx & mask;
443	to_submit++;
444	}
445
446	// Increment the tail based on how many we are ready to submit
447	__atomic_fetch_add(ring.submit_q.tail, to_submit, __ATOMIC_SEQ_CST);
448	}
449
450	const uint32_t smask = *ring.submit_q.mask;
451	uint32_t shead = *ring.submit_q.head;
452	int ret = syscall( __NR_io_uring_enter, ring.fd, to_submit, waitcnt, IORING_ENTER_GETEVENTS, mask, _NSIG / 8);
453	if( ret < 0 ) {
454	switch((int)errno) {
455	case EAGAIN:
456	case EINTR:
457	return -EAGAIN;
458	default:
459	abort( "KERNEL ERROR: IO_URING WAIT - %s\n", strerror(errno) );
460	}
461	}
462
463	// Release the consumed SQEs
464	for( i; ret ) {
465	uint32_t idx = ring.submit_q.array[ (i + shead) & smask ];
466	ring.submit_q.sqes[ idx ].user_data = 0;
467	}
468
469	uint32_t avail = 0;
470	uint32_t sqe_num = *ring.submit_q.num;
471	for(i; sqe_num) {
472	if( ring.submit_q.sqes[ i ].user_data == 0 ) avail++;
473	}
474
475	// update statistics
476	#if !defined(__CFA_NO_STATISTICS__)
477	__tls_stats()->io.submit_q.submit_avg.rdy += to_submit;
478	__tls_stats()->io.submit_q.submit_avg.csm += ret;
479	__tls_stats()->io.submit_q.submit_avg.avl += avail;
480	__tls_stats()->io.submit_q.submit_avg.cnt += 1;
481	#endif
482
483	// Drain the queue
484	unsigned head = *ring.completion_q.head;
485	unsigned tail = *ring.completion_q.tail;
486	const uint32_t mask = *ring.completion_q.mask;
487
488	// Memory barrier
489	__atomic_thread_fence( __ATOMIC_SEQ_CST );
490
491	// Nothing was new return 0
492	if (head == tail) {
493	return 0;
494	}
495
496	uint32_t count = tail - head;
497	for(i; count) {
498	unsigned idx = (head + i) & mask;
499	struct io_uring_cqe & cqe = ring.completion_q.cqes[idx];
500
501	/* paranoid */ verify(&cqe);
502
503	struct __io_user_data_t * data = (struct __io_user_data_t *)(uintptr_t)cqe.user_data;
504	__cfadbg_print_safe( io, "Kernel I/O : Performed reading io cqe %p, result %d for %p\n", data, cqe.res, data->thrd );
505
506	data->result = cqe.res;
507	if(!in_kernel) { unpark( data->thrd __cfaabi_dbg_ctx2 ); }
508	else { __unpark( &ring.poller.slow.id, data->thrd __cfaabi_dbg_ctx2 ); }
509	}
510
511	// Allow new submissions to happen
512	// V(ring.submit, count);
513
514	// Mark to the kernel that the cqe has been seen
515	// Ensure that the kernel only sees the new value of the head index after the CQEs have been read.
516	__atomic_thread_fence( __ATOMIC_SEQ_CST );
517	__atomic_fetch_add( ring.completion_q.head, count, __ATOMIC_RELAXED );
518
519	return [count, count > 0 \|\| to_submit > 0];
520	}
521
522	static void * __io_poller_slow( void * arg ) {
523	#if !defined( __CFA_NO_STATISTICS__ )
524	__stats_t local_stats;
525	__init_stats( &local_stats );
526	kernelTLS.this_stats = &local_stats;
527	#endif
528
529	cluster * cltr = (cluster *)arg;
530	struct __io_data & ring = *cltr->io;
531
532	ring.poller.slow.id.id = doregister( &ring.poller.slow.id );
533
534	sigset_t mask;
535	sigfillset(&mask);
536	if ( pthread_sigmask( SIG_BLOCK, &mask, 0p ) == -1 ) {
537	abort( "KERNEL ERROR: IO_URING - pthread_sigmask" );
538	}
539
540	sigdelset( &mask, SIGUSR1 );
541
542	verify( (ring.submit_q.head) == (ring.submit_q.tail) );
543	verify( (ring.completion_q.head) == (ring.completion_q.tail) );
544
545	__cfadbg_print_safe(io_core, "Kernel I/O : Slow poller for ring %p ready\n", &ring);
546
547	if( ring.cltr_flags & CFA_CLUSTER_IO_POLLER_USER_THREAD ) {
548	while(!__atomic_load_n(&ring.done, __ATOMIC_SEQ_CST)) {
549
550	__atomic_store_n( &ring.poller.slow.blocked, true, __ATOMIC_SEQ_CST );
551
552	// In the user-thread approach drain and if anything was drained,
553	// batton pass to the user-thread
554	int count;
555	bool again;
556	[count, again] = __drain_io( ring, &mask, 1, true );
557
558	__atomic_store_n( &ring.poller.slow.blocked, false, __ATOMIC_SEQ_CST );
559
560	// Update statistics
561	#if !defined(__CFA_NO_STATISTICS__)
562	__tls_stats()->io.complete_q.completed_avg.val += count;
563	__tls_stats()->io.complete_q.completed_avg.slow_cnt += 1;
564	#endif
565
566	if(again) {
567	__cfadbg_print_safe(io_core, "Kernel I/O : Moving to ring %p to fast poller\n", &ring);
568	__unpark( &ring.poller.slow.id, &ring.poller.fast.thrd __cfaabi_dbg_ctx2 );
569	wait( ring.poller.sem );
570	}
571	}
572	}
573	else {
574	while(!__atomic_load_n(&ring.done, __ATOMIC_SEQ_CST)) {
575	//In the naive approach, just poll the io completion queue directly
576	int count;
577	bool again;
578	[count, again] = __drain_io( ring, &mask, 0, true );
579
580	// Update statistics
581	#if !defined(__CFA_NO_STATISTICS__)
582	__tls_stats()->io.complete_q.completed_avg.val += count;
583	__tls_stats()->io.complete_q.completed_avg.slow_cnt += 1;
584	#endif
585	}
586	}
587
588	__cfadbg_print_safe(io_core, "Kernel I/O : Slow poller for ring %p stopping\n", &ring);
589
590	unregister( &ring.poller.slow.id );
591
592	#if !defined(__CFA_NO_STATISTICS__)
593	__tally_stats(cltr->stats, &local_stats);
594	#endif
595
596	return 0p;
597	}
598
599	void main( __io_poller_fast & this ) {
600	verify( this.ring->cltr_flags & CFA_CLUSTER_IO_POLLER_USER_THREAD );
601
602	// Start parked
603	park( __cfaabi_dbg_ctx );
604
605	__cfadbg_print_safe(io_core, "Kernel I/O : Fast poller for ring %p ready\n", &this.ring);
606
607	int reset = 0;
608
609	// Then loop until we need to start
610	while(!__atomic_load_n(&this.ring->done, __ATOMIC_SEQ_CST)) {
611
612	// Drain the io
613	int count;
614	bool again;
615	disable_interrupts();
616	[count, again] = __drain_io( *this.ring, 0p, 0, false );
617
618	if(!again) reset++;
619
620	// Update statistics
621	#if !defined(__CFA_NO_STATISTICS__)
622	__tls_stats()->io.complete_q.completed_avg.val += count;
623	__tls_stats()->io.complete_q.completed_avg.fast_cnt += 1;
624	#endif
625	enable_interrupts( __cfaabi_dbg_ctx );
626
627	// If we got something, just yield and check again
628	if(reset < 5) {
629	yield();
630	}
631	// We didn't get anything baton pass to the slow poller
632	else {
633	__cfadbg_print_safe(io_core, "Kernel I/O : Moving to ring %p to slow poller\n", &this.ring);
634	reset = 0;
635
636	// wake up the slow poller
637	post( this.ring->poller.sem );
638
639	// park this thread
640	park( __cfaabi_dbg_ctx );
641	}
642	}
643
644	__cfadbg_print_safe(io_core, "Kernel I/O : Fast poller for ring %p stopping\n", &this.ring);
645	}
646
647	static inline void __wake_poller( struct __io_data & ring ) __attribute__((artificial));
648	static inline void __wake_poller( struct __io_data & ring ) {
649	if(!__atomic_load_n( &ring.poller.slow.blocked, __ATOMIC_SEQ_CST)) return;
650
651	sigval val = { 1 };
652	pthread_sigqueue( ring.poller.slow.kthrd, SIGUSR1, val );
653	}
654
655	//=============================================================================================
656	// I/O Submissions
657	//=============================================================================================
658
659	// Submition steps :
660	// 1 - We need to make sure we don't overflow any of the buffer, P(ring.submit) to make sure
661	// entries are available. The semaphore make sure that there is no more operations in
662	// progress then the number of entries in the buffer. This probably limits concurrency
663	// more than necessary since submitted but not completed operations don't need any
664	// entries in user space. However, I don't know what happens if we overflow the buffers
665	// because too many requests completed at once. This is a safe approach in all cases.
666	// Furthermore, with hundreds of entries, this may be okay.
667	//
668	// 2 - Allocate a queue entry. The ring already has memory for all entries but only the ones
669	// listed in sq.array are visible by the kernel. For those not listed, the kernel does not
670	// offer any assurance that an entry is not being filled by multiple flags. Therefore, we
671	// need to write an allocator that allows allocating concurrently.
672	//
673	// 3 - Actually fill the submit entry, this is the only simple and straightforward step.
674	//
675	// 4 - Append the entry index to the array and adjust the tail accordingly. This operation
676	// needs to arrive to two concensus at the same time:
677	// A - The order in which entries are listed in the array: no two threads must pick the
678	// same index for their entries
679	// B - When can the tail be update for the kernel. EVERY entries in the array between
680	// head and tail must be fully filled and shouldn't ever be touched again.
681	//
682
683	[* struct io_uring_sqe, uint32_t] __submit_alloc( struct __io_data & ring, uint64_t data ) {
684	verify( data != 0 );
685
686
687	// Prepare the data we need
688	__attribute((unused)) int len = 0;
689	__attribute((unused)) int block = 0;
690	uint32_t cnt = *ring.submit_q.num;
691	uint32_t mask = *ring.submit_q.mask;
692
693	disable_interrupts();
694	uint32_t off = __tls_rand();
695	enable_interrupts( __cfaabi_dbg_ctx );
696
697	// Loop around looking for an available spot
698	for() {
699	// Look through the list starting at some offset
700	for(i; cnt) {
701	uint64_t expected = 0;
702	uint32_t idx = (i + off) & mask;
703	struct io_uring_sqe * sqe = &ring.submit_q.sqes[idx];
704	volatile uint64_t * udata = &sqe->user_data;
705
706	if( *udata == expected &&
707	__atomic_compare_exchange_n( udata, &expected, data, true, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED ) )
708	{
709	// update statistics
710	#if !defined(__CFA_NO_STATISTICS__)
711	disable_interrupts();
712	__tls_stats()->io.submit_q.alloc_avg.val += len;
713	__tls_stats()->io.submit_q.alloc_avg.block += block;
714	__tls_stats()->io.submit_q.alloc_avg.cnt += 1;
715	enable_interrupts( __cfaabi_dbg_ctx );
716	#endif
717
718
719	// Success return the data
720	return [sqe, idx];
721	}
722	verify(expected != data);
723
724	len ++;
725	}
726
727	block++;
728	yield();
729	}
730	}
731
732	static inline uint32_t __submit_to_ready_array( struct __io_data & ring, uint32_t idx, const uint32_t mask ) {
733	/* paranoid */ verify( idx <= mask );
734	/* paranoid */ verify( idx != -1ul32 );
735
736	// We need to find a spot in the ready array
737	__attribute((unused)) int len = 0;
738	__attribute((unused)) int block = 0;
739	uint32_t ready_mask = ring.submit_q.ready_cnt - 1;
740
741	disable_interrupts();
742	uint32_t off = __tls_rand();
743	enable_interrupts( __cfaabi_dbg_ctx );
744
745	uint32_t picked;
746	LOOKING: for() {
747	for(i; ring.submit_q.ready_cnt) {
748	picked = (i + off) & ready_mask;
749	uint32_t expected = -1ul32;
750	if( __atomic_compare_exchange_n( &ring.submit_q.ready[picked], &expected, idx, true, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED ) ) {
751	break LOOKING;
752	}
753	verify(expected != idx);
754
755	len ++;
756	}
757
758	block++;
759	yield();
760	}
761
762	// update statistics
763	#if !defined(__CFA_NO_STATISTICS__)
764	disable_interrupts();
765	__tls_stats()->io.submit_q.look_avg.val += len;
766	__tls_stats()->io.submit_q.look_avg.block += block;
767	__tls_stats()->io.submit_q.look_avg.cnt += 1;
768	enable_interrupts( __cfaabi_dbg_ctx );
769	#endif
770
771	return picked;
772	}
773
774	void __submit( struct __io_data & ring, uint32_t idx ) {
775	// Get now the data we definetely need
776	uint32_t * const tail = ring.submit_q.tail;
777	const uint32_t mask = *ring.submit_q.mask;
778
779	// There are 2 submission schemes, check which one we are using
780	if( ring.cltr_flags & CFA_CLUSTER_IO_POLLER_THREAD_SUBMITS ) {
781	// If the poller thread submits, then we just need to add this to the ready array
782
783	__submit_to_ready_array( ring, idx, mask );
784
785	__wake_poller( ring );
786
787	__cfadbg_print_safe( io, "Kernel I/O : Added %u to ready for %p\n", idx, active_thread() );
788	}
789	else {
790	// get mutual exclusion
791	lock(ring.submit_q.lock __cfaabi_dbg_ctx2);
792
793	// Append to the list of ready entries
794
795	/* paranoid */ verify( idx <= mask );
796
797	ring.submit_q.array[ (*tail) & mask ] = idx & mask;
798	__atomic_fetch_add(tail, 1ul32, __ATOMIC_SEQ_CST);
799
800	// Submit however, many entries need to be submitted
801	int ret = syscall( __NR_io_uring_enter, ring.fd, 1, 0, 0, 0p, 0);
802	if( ret < 0 ) {
803	switch((int)errno) {
804	default:
805	abort( "KERNEL ERROR: IO_URING SUBMIT - %s\n", strerror(errno) );
806	}
807	}
808
809	// update statistics
810	#if !defined(__CFA_NO_STATISTICS__)
811	__tls_stats()->io.submit_q.submit_avg.csm += 1;
812	__tls_stats()->io.submit_q.submit_avg.cnt += 1;
813	#endif
814
815	ring.submit_q.sqes[ idx & mask ].user_data = 0;
816
817	unlock(ring.submit_q.lock);
818
819	__cfadbg_print_safe( io, "Kernel I/O : Performed io_submit for %p, returned %d\n", active_thread(), ret );
820	}
821	}
822	#endif

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