xref: /freebsd/sys/kern/subr_devstat.c (revision 4c9e27bd0a5f7fda85b0c0bf750575aee300a172)
1 /*-
2  * Copyright (c) 1997, 1998, 1999 Kenneth D. Merry.
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. The name of the author may not be used to endorse or promote products
14  *    derived from this software without specific prior written permission.
15  *
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26  * SUCH DAMAGE.
27  */
28 
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD$");
31 
32 #include "opt_kdtrace.h"
33 
34 #include <sys/param.h>
35 #include <sys/kernel.h>
36 #include <sys/systm.h>
37 #include <sys/bio.h>
38 #include <sys/devicestat.h>
39 #include <sys/sdt.h>
40 #include <sys/sysctl.h>
41 #include <sys/malloc.h>
42 #include <sys/lock.h>
43 #include <sys/mutex.h>
44 #include <sys/conf.h>
45 #include <vm/vm.h>
46 #include <vm/pmap.h>
47 
48 #include <machine/atomic.h>
49 
50 SDT_PROVIDER_DEFINE(io);
51 
52 SDT_PROBE_DEFINE2(io, , , start, start, "struct bio *", "struct devstat *");
53 SDT_PROBE_DEFINE2(io, , , done, done, "struct bio *", "struct devstat *");
54 SDT_PROBE_DEFINE2(io, , , wait_start, wait-start, "struct bio *",
55     "struct devstat *");
56 SDT_PROBE_DEFINE2(io, , , wait_done, wait-done, "struct bio *",
57     "struct devstat *");
58 
59 #define	DTRACE_DEVSTAT_START()		SDT_PROBE2(io, , , start, NULL, ds)
60 #define	DTRACE_DEVSTAT_BIO_START()	SDT_PROBE2(io, , , start, bp, ds)
61 #define	DTRACE_DEVSTAT_DONE()		SDT_PROBE2(io, , , done, NULL, ds)
62 #define	DTRACE_DEVSTAT_BIO_DONE()	SDT_PROBE2(io, , , done, bp, ds)
63 #define	DTRACE_DEVSTAT_WAIT_START()	SDT_PROBE2(io, , , wait_start, NULL, ds)
64 #define	DTRACE_DEVSTAT_WAIT_DONE()	SDT_PROBE2(io, , , wait_done, NULL, ds)
65 
66 static int devstat_num_devs;
67 static long devstat_generation = 1;
68 static int devstat_version = DEVSTAT_VERSION;
69 static int devstat_current_devnumber;
70 static struct mtx devstat_mutex;
71 MTX_SYSINIT(devstat_mutex, &devstat_mutex, "devstat", MTX_DEF);
72 
73 static struct devstatlist device_statq = STAILQ_HEAD_INITIALIZER(device_statq);
74 static struct devstat *devstat_alloc(void);
75 static void devstat_free(struct devstat *);
76 static void devstat_add_entry(struct devstat *ds, const void *dev_name,
77 		       int unit_number, uint32_t block_size,
78 		       devstat_support_flags flags,
79 		       devstat_type_flags device_type,
80 		       devstat_priority priority);
81 
82 /*
83  * Allocate a devstat and initialize it
84  */
85 struct devstat *
86 devstat_new_entry(const void *dev_name,
87 		  int unit_number, uint32_t block_size,
88 		  devstat_support_flags flags,
89 		  devstat_type_flags device_type,
90 		  devstat_priority priority)
91 {
92 	struct devstat *ds;
93 
94 	mtx_assert(&devstat_mutex, MA_NOTOWNED);
95 
96 	ds = devstat_alloc();
97 	mtx_lock(&devstat_mutex);
98 	if (unit_number == -1) {
99 		ds->unit_number = unit_number;
100 		ds->id = dev_name;
101 		binuptime(&ds->creation_time);
102 		devstat_generation++;
103 	} else {
104 		devstat_add_entry(ds, dev_name, unit_number, block_size,
105 				  flags, device_type, priority);
106 	}
107 	mtx_unlock(&devstat_mutex);
108 	return (ds);
109 }
110 
111 /*
112  * Take a malloced and zeroed devstat structure given to us, fill it in
113  * and add it to the queue of devices.
114  */
115 static void
116 devstat_add_entry(struct devstat *ds, const void *dev_name,
117 		  int unit_number, uint32_t block_size,
118 		  devstat_support_flags flags,
119 		  devstat_type_flags device_type,
120 		  devstat_priority priority)
121 {
122 	struct devstatlist *devstat_head;
123 	struct devstat *ds_tmp;
124 
125 	mtx_assert(&devstat_mutex, MA_OWNED);
126 	devstat_num_devs++;
127 
128 	devstat_head = &device_statq;
129 
130 	/*
131 	 * Priority sort.  Each driver passes in its priority when it adds
132 	 * its devstat entry.  Drivers are sorted first by priority, and
133 	 * then by probe order.
134 	 *
135 	 * For the first device, we just insert it, since the priority
136 	 * doesn't really matter yet.  Subsequent devices are inserted into
137 	 * the list using the order outlined above.
138 	 */
139 	if (devstat_num_devs == 1)
140 		STAILQ_INSERT_TAIL(devstat_head, ds, dev_links);
141 	else {
142 		STAILQ_FOREACH(ds_tmp, devstat_head, dev_links) {
143 			struct devstat *ds_next;
144 
145 			ds_next = STAILQ_NEXT(ds_tmp, dev_links);
146 
147 			/*
148 			 * If we find a break between higher and lower
149 			 * priority items, and if this item fits in the
150 			 * break, insert it.  This also applies if the
151 			 * "lower priority item" is the end of the list.
152 			 */
153 			if ((priority <= ds_tmp->priority)
154 			 && ((ds_next == NULL)
155 			   || (priority > ds_next->priority))) {
156 				STAILQ_INSERT_AFTER(devstat_head, ds_tmp, ds,
157 						    dev_links);
158 				break;
159 			} else if (priority > ds_tmp->priority) {
160 				/*
161 				 * If this is the case, we should be able
162 				 * to insert ourselves at the head of the
163 				 * list.  If we can't, something is wrong.
164 				 */
165 				if (ds_tmp == STAILQ_FIRST(devstat_head)) {
166 					STAILQ_INSERT_HEAD(devstat_head,
167 							   ds, dev_links);
168 					break;
169 				} else {
170 					STAILQ_INSERT_TAIL(devstat_head,
171 							   ds, dev_links);
172 					printf("devstat_add_entry: HELP! "
173 					       "sorting problem detected "
174 					       "for name %p unit %d\n",
175 					       dev_name, unit_number);
176 					break;
177 				}
178 			}
179 		}
180 	}
181 
182 	ds->device_number = devstat_current_devnumber++;
183 	ds->unit_number = unit_number;
184 	strlcpy(ds->device_name, dev_name, DEVSTAT_NAME_LEN);
185 	ds->block_size = block_size;
186 	ds->flags = flags;
187 	ds->device_type = device_type;
188 	ds->priority = priority;
189 	binuptime(&ds->creation_time);
190 	devstat_generation++;
191 }
192 
193 /*
194  * Remove a devstat structure from the list of devices.
195  */
196 void
197 devstat_remove_entry(struct devstat *ds)
198 {
199 	struct devstatlist *devstat_head;
200 
201 	mtx_assert(&devstat_mutex, MA_NOTOWNED);
202 	if (ds == NULL)
203 		return;
204 
205 	mtx_lock(&devstat_mutex);
206 
207 	devstat_head = &device_statq;
208 
209 	/* Remove this entry from the devstat queue */
210 	atomic_add_acq_int(&ds->sequence1, 1);
211 	if (ds->unit_number != -1) {
212 		devstat_num_devs--;
213 		STAILQ_REMOVE(devstat_head, ds, devstat, dev_links);
214 	}
215 	devstat_free(ds);
216 	devstat_generation++;
217 	mtx_unlock(&devstat_mutex);
218 }
219 
220 /*
221  * Record a transaction start.
222  *
223  * See comments for devstat_end_transaction().  Ordering is very important
224  * here.
225  */
226 void
227 devstat_start_transaction(struct devstat *ds, struct bintime *now)
228 {
229 
230 	mtx_assert(&devstat_mutex, MA_NOTOWNED);
231 
232 	/* sanity check */
233 	if (ds == NULL)
234 		return;
235 
236 	atomic_add_acq_int(&ds->sequence1, 1);
237 	/*
238 	 * We only want to set the start time when we are going from idle
239 	 * to busy.  The start time is really the start of the latest busy
240 	 * period.
241 	 */
242 	if (ds->start_count == ds->end_count) {
243 		if (now != NULL)
244 			ds->busy_from = *now;
245 		else
246 			binuptime(&ds->busy_from);
247 	}
248 	ds->start_count++;
249 	atomic_add_rel_int(&ds->sequence0, 1);
250 	DTRACE_DEVSTAT_START();
251 }
252 
253 void
254 devstat_start_transaction_bio(struct devstat *ds, struct bio *bp)
255 {
256 
257 	mtx_assert(&devstat_mutex, MA_NOTOWNED);
258 
259 	/* sanity check */
260 	if (ds == NULL)
261 		return;
262 
263 	binuptime(&bp->bio_t0);
264 	devstat_start_transaction(ds, &bp->bio_t0);
265 	DTRACE_DEVSTAT_BIO_START();
266 }
267 
268 /*
269  * Record the ending of a transaction, and incrment the various counters.
270  *
271  * Ordering in this function, and in devstat_start_transaction() is VERY
272  * important.  The idea here is to run without locks, so we are very
273  * careful to only modify some fields on the way "down" (i.e. at
274  * transaction start) and some fields on the way "up" (i.e. at transaction
275  * completion).  One exception is busy_from, which we only modify in
276  * devstat_start_transaction() when there are no outstanding transactions,
277  * and thus it can't be modified in devstat_end_transaction()
278  * simultaneously.
279  *
280  * The sequence0 and sequence1 fields are provided to enable an application
281  * spying on the structures with mmap(2) to tell when a structure is in a
282  * consistent state or not.
283  *
284  * For this to work 100% reliably, it is important that the two fields
285  * are at opposite ends of the structure and that they are incremented
286  * in the opposite order of how a memcpy(3) in userland would copy them.
287  * We assume that the copying happens front to back, but there is actually
288  * no way short of writing your own memcpy(3) replacement to guarantee
289  * this will be the case.
290  *
291  * In addition to this, being a kind of locks, they must be updated with
292  * atomic instructions using appropriate memory barriers.
293  */
294 void
295 devstat_end_transaction(struct devstat *ds, uint32_t bytes,
296 			devstat_tag_type tag_type, devstat_trans_flags flags,
297 			struct bintime *now, struct bintime *then)
298 {
299 	struct bintime dt, lnow;
300 
301 	/* sanity check */
302 	if (ds == NULL)
303 		return;
304 
305 	if (now == NULL) {
306 		now = &lnow;
307 		binuptime(now);
308 	}
309 
310 	atomic_add_acq_int(&ds->sequence1, 1);
311 	/* Update byte and operations counts */
312 	ds->bytes[flags] += bytes;
313 	ds->operations[flags]++;
314 
315 	/*
316 	 * Keep a count of the various tag types sent.
317 	 */
318 	if ((ds->flags & DEVSTAT_NO_ORDERED_TAGS) == 0 &&
319 	    tag_type != DEVSTAT_TAG_NONE)
320 		ds->tag_types[tag_type]++;
321 
322 	if (then != NULL) {
323 		/* Update duration of operations */
324 		dt = *now;
325 		bintime_sub(&dt, then);
326 		bintime_add(&ds->duration[flags], &dt);
327 	}
328 
329 	/* Accumulate busy time */
330 	dt = *now;
331 	bintime_sub(&dt, &ds->busy_from);
332 	bintime_add(&ds->busy_time, &dt);
333 	ds->busy_from = *now;
334 
335 	ds->end_count++;
336 	atomic_add_rel_int(&ds->sequence0, 1);
337 	DTRACE_DEVSTAT_DONE();
338 }
339 
340 void
341 devstat_end_transaction_bio(struct devstat *ds, struct bio *bp)
342 {
343 
344 	devstat_end_transaction_bio_bt(ds, bp, NULL);
345 }
346 
347 void
348 devstat_end_transaction_bio_bt(struct devstat *ds, struct bio *bp,
349     struct bintime *now)
350 {
351 	devstat_trans_flags flg;
352 
353 	/* sanity check */
354 	if (ds == NULL)
355 		return;
356 
357 	if (bp->bio_cmd == BIO_DELETE)
358 		flg = DEVSTAT_FREE;
359 	else if (bp->bio_cmd == BIO_READ)
360 		flg = DEVSTAT_READ;
361 	else if (bp->bio_cmd == BIO_WRITE)
362 		flg = DEVSTAT_WRITE;
363 	else
364 		flg = DEVSTAT_NO_DATA;
365 
366 	devstat_end_transaction(ds, bp->bio_bcount - bp->bio_resid,
367 				DEVSTAT_TAG_SIMPLE, flg, now, &bp->bio_t0);
368 	DTRACE_DEVSTAT_BIO_DONE();
369 }
370 
371 /*
372  * This is the sysctl handler for the devstat package.  The data pushed out
373  * on the kern.devstat.all sysctl variable consists of the current devstat
374  * generation number, and then an array of devstat structures, one for each
375  * device in the system.
376  *
377  * This is more cryptic that obvious, but basically we neither can nor
378  * want to hold the devstat_mutex for any amount of time, so we grab it
379  * only when we need to and keep an eye on devstat_generation all the time.
380  */
381 static int
382 sysctl_devstat(SYSCTL_HANDLER_ARGS)
383 {
384 	int error;
385 	long mygen;
386 	struct devstat *nds;
387 
388 	mtx_assert(&devstat_mutex, MA_NOTOWNED);
389 
390 	/*
391 	 * XXX devstat_generation should really be "volatile" but that
392 	 * XXX freaks out the sysctl macro below.  The places where we
393 	 * XXX change it and inspect it are bracketed in the mutex which
394 	 * XXX guarantees us proper write barriers.  I don't belive the
395 	 * XXX compiler is allowed to optimize mygen away across calls
396 	 * XXX to other functions, so the following is belived to be safe.
397 	 */
398 	mygen = devstat_generation;
399 
400 	error = SYSCTL_OUT(req, &mygen, sizeof(mygen));
401 
402 	if (devstat_num_devs == 0)
403 		return(0);
404 
405 	if (error != 0)
406 		return (error);
407 
408 	mtx_lock(&devstat_mutex);
409 	nds = STAILQ_FIRST(&device_statq);
410 	if (mygen != devstat_generation)
411 		error = EBUSY;
412 	mtx_unlock(&devstat_mutex);
413 
414 	if (error != 0)
415 		return (error);
416 
417 	for (;nds != NULL;) {
418 		error = SYSCTL_OUT(req, nds, sizeof(struct devstat));
419 		if (error != 0)
420 			return (error);
421 		mtx_lock(&devstat_mutex);
422 		if (mygen != devstat_generation)
423 			error = EBUSY;
424 		else
425 			nds = STAILQ_NEXT(nds, dev_links);
426 		mtx_unlock(&devstat_mutex);
427 		if (error != 0)
428 			return (error);
429 	}
430 	return(error);
431 }
432 
433 /*
434  * Sysctl entries for devstat.  The first one is a node that all the rest
435  * hang off of.
436  */
437 static SYSCTL_NODE(_kern, OID_AUTO, devstat, CTLFLAG_RD, NULL,
438     "Device Statistics");
439 
440 SYSCTL_PROC(_kern_devstat, OID_AUTO, all, CTLFLAG_RD|CTLTYPE_OPAQUE,
441     NULL, 0, sysctl_devstat, "S,devstat", "All devices in the devstat list");
442 /*
443  * Export the number of devices in the system so that userland utilities
444  * can determine how much memory to allocate to hold all the devices.
445  */
446 SYSCTL_INT(_kern_devstat, OID_AUTO, numdevs, CTLFLAG_RD,
447     &devstat_num_devs, 0, "Number of devices in the devstat list");
448 SYSCTL_LONG(_kern_devstat, OID_AUTO, generation, CTLFLAG_RD,
449     &devstat_generation, 0, "Devstat list generation");
450 SYSCTL_INT(_kern_devstat, OID_AUTO, version, CTLFLAG_RD,
451     &devstat_version, 0, "Devstat list version number");
452 
453 /*
454  * Allocator for struct devstat structures.  We sub-allocate these from pages
455  * which we get from malloc.  These pages are exported for mmap(2)'ing through
456  * a miniature device driver
457  */
458 
459 #define statsperpage (PAGE_SIZE / sizeof(struct devstat))
460 
461 static d_mmap_t devstat_mmap;
462 
463 static struct cdevsw devstat_cdevsw = {
464 	.d_version =	D_VERSION,
465 	.d_flags =	D_NEEDGIANT,
466 	.d_mmap =	devstat_mmap,
467 	.d_name =	"devstat",
468 };
469 
470 struct statspage {
471 	TAILQ_ENTRY(statspage)	list;
472 	struct devstat		*stat;
473 	u_int			nfree;
474 };
475 
476 static TAILQ_HEAD(, statspage)	pagelist = TAILQ_HEAD_INITIALIZER(pagelist);
477 static MALLOC_DEFINE(M_DEVSTAT, "devstat", "Device statistics");
478 
479 static int
480 devstat_mmap(struct cdev *dev, vm_ooffset_t offset, vm_paddr_t *paddr,
481     int nprot, vm_memattr_t *memattr)
482 {
483 	struct statspage *spp;
484 
485 	if (nprot != VM_PROT_READ)
486 		return (-1);
487 	TAILQ_FOREACH(spp, &pagelist, list) {
488 		if (offset == 0) {
489 			*paddr = vtophys(spp->stat);
490 			return (0);
491 		}
492 		offset -= PAGE_SIZE;
493 	}
494 	return (-1);
495 }
496 
497 static struct devstat *
498 devstat_alloc(void)
499 {
500 	struct devstat *dsp;
501 	struct statspage *spp, *spp2;
502 	u_int u;
503 	static int once;
504 
505 	mtx_assert(&devstat_mutex, MA_NOTOWNED);
506 	if (!once) {
507 		make_dev_credf(MAKEDEV_ETERNAL | MAKEDEV_CHECKNAME,
508 		    &devstat_cdevsw, 0, NULL, UID_ROOT, GID_WHEEL, 0400,
509 		    DEVSTAT_DEVICE_NAME);
510 		once = 1;
511 	}
512 	spp2 = NULL;
513 	mtx_lock(&devstat_mutex);
514 	for (;;) {
515 		TAILQ_FOREACH(spp, &pagelist, list) {
516 			if (spp->nfree > 0)
517 				break;
518 		}
519 		if (spp != NULL)
520 			break;
521 		mtx_unlock(&devstat_mutex);
522 		spp2 = malloc(sizeof *spp, M_DEVSTAT, M_ZERO | M_WAITOK);
523 		spp2->stat = malloc(PAGE_SIZE, M_DEVSTAT, M_ZERO | M_WAITOK);
524 		spp2->nfree = statsperpage;
525 
526 		/*
527 		 * If free statspages were added while the lock was released
528 		 * just reuse them.
529 		 */
530 		mtx_lock(&devstat_mutex);
531 		TAILQ_FOREACH(spp, &pagelist, list)
532 			if (spp->nfree > 0)
533 				break;
534 		if (spp == NULL) {
535 			spp = spp2;
536 
537 			/*
538 			 * It would make more sense to add the new page at the
539 			 * head but the order on the list determine the
540 			 * sequence of the mapping so we can't do that.
541 			 */
542 			TAILQ_INSERT_TAIL(&pagelist, spp, list);
543 		} else
544 			break;
545 	}
546 	dsp = spp->stat;
547 	for (u = 0; u < statsperpage; u++) {
548 		if (dsp->allocated == 0)
549 			break;
550 		dsp++;
551 	}
552 	spp->nfree--;
553 	dsp->allocated = 1;
554 	mtx_unlock(&devstat_mutex);
555 	if (spp2 != NULL && spp2 != spp) {
556 		free(spp2->stat, M_DEVSTAT);
557 		free(spp2, M_DEVSTAT);
558 	}
559 	return (dsp);
560 }
561 
562 static void
563 devstat_free(struct devstat *dsp)
564 {
565 	struct statspage *spp;
566 
567 	mtx_assert(&devstat_mutex, MA_OWNED);
568 	bzero(dsp, sizeof *dsp);
569 	TAILQ_FOREACH(spp, &pagelist, list) {
570 		if (dsp >= spp->stat && dsp < (spp->stat + statsperpage)) {
571 			spp->nfree++;
572 			return;
573 		}
574 	}
575 }
576 
577 SYSCTL_INT(_debug_sizeof, OID_AUTO, devstat, CTLFLAG_RD,
578     NULL, sizeof(struct devstat), "sizeof(struct devstat)");
579