The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_devstat.c

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    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: releng/9.0/sys/kern/subr_devstat.c 223062 2011-06-13 22:08:24Z ken $");
   31 
   32 #include <sys/param.h>
   33 #include <sys/kernel.h>
   34 #include <sys/systm.h>
   35 #include <sys/bio.h>
   36 #include <sys/devicestat.h>
   37 #include <sys/sysctl.h>
   38 #include <sys/malloc.h>
   39 #include <sys/lock.h>
   40 #include <sys/mutex.h>
   41 #include <sys/conf.h>
   42 #include <vm/vm.h>
   43 #include <vm/pmap.h>
   44 
   45 #include <machine/atomic.h>
   46 
   47 static int devstat_num_devs;
   48 static long devstat_generation = 1;
   49 static int devstat_version = DEVSTAT_VERSION;
   50 static int devstat_current_devnumber;
   51 static struct mtx devstat_mutex;
   52 MTX_SYSINIT(devstat_mutex, &devstat_mutex, "devstat", MTX_DEF);
   53 
   54 static struct devstatlist device_statq = STAILQ_HEAD_INITIALIZER(device_statq);
   55 static struct devstat *devstat_alloc(void);
   56 static void devstat_free(struct devstat *);
   57 static void devstat_add_entry(struct devstat *ds, const void *dev_name, 
   58                        int unit_number, uint32_t block_size,
   59                        devstat_support_flags flags,
   60                        devstat_type_flags device_type,
   61                        devstat_priority priority);
   62 
   63 /*
   64  * Allocate a devstat and initialize it
   65  */
   66 struct devstat *
   67 devstat_new_entry(const void *dev_name,
   68                   int unit_number, uint32_t block_size,
   69                   devstat_support_flags flags,
   70                   devstat_type_flags device_type,
   71                   devstat_priority priority)
   72 {
   73         struct devstat *ds;
   74 
   75         mtx_assert(&devstat_mutex, MA_NOTOWNED);
   76 
   77         ds = devstat_alloc();
   78         mtx_lock(&devstat_mutex);
   79         if (unit_number == -1) {
   80                 ds->id = dev_name;
   81                 binuptime(&ds->creation_time);
   82                 devstat_generation++;
   83         } else {
   84                 devstat_add_entry(ds, dev_name, unit_number, block_size,
   85                                   flags, device_type, priority);
   86         }
   87         mtx_unlock(&devstat_mutex);
   88         return (ds);
   89 }
   90 
   91 /*
   92  * Take a malloced and zeroed devstat structure given to us, fill it in 
   93  * and add it to the queue of devices.  
   94  */
   95 static void
   96 devstat_add_entry(struct devstat *ds, const void *dev_name, 
   97                   int unit_number, uint32_t block_size,
   98                   devstat_support_flags flags,
   99                   devstat_type_flags device_type,
  100                   devstat_priority priority)
  101 {
  102         struct devstatlist *devstat_head;
  103         struct devstat *ds_tmp;
  104 
  105         mtx_assert(&devstat_mutex, MA_OWNED);
  106         devstat_num_devs++;
  107 
  108         devstat_head = &device_statq;
  109 
  110         /*
  111          * Priority sort.  Each driver passes in its priority when it adds
  112          * its devstat entry.  Drivers are sorted first by priority, and
  113          * then by probe order.
  114          * 
  115          * For the first device, we just insert it, since the priority
  116          * doesn't really matter yet.  Subsequent devices are inserted into
  117          * the list using the order outlined above.
  118          */
  119         if (devstat_num_devs == 1)
  120                 STAILQ_INSERT_TAIL(devstat_head, ds, dev_links);
  121         else {
  122                 STAILQ_FOREACH(ds_tmp, devstat_head, dev_links) {
  123                         struct devstat *ds_next;
  124 
  125                         ds_next = STAILQ_NEXT(ds_tmp, dev_links);
  126 
  127                         /*
  128                          * If we find a break between higher and lower
  129                          * priority items, and if this item fits in the
  130                          * break, insert it.  This also applies if the
  131                          * "lower priority item" is the end of the list.
  132                          */
  133                         if ((priority <= ds_tmp->priority)
  134                          && ((ds_next == NULL)
  135                            || (priority > ds_next->priority))) {
  136                                 STAILQ_INSERT_AFTER(devstat_head, ds_tmp, ds,
  137                                                     dev_links);
  138                                 break;
  139                         } else if (priority > ds_tmp->priority) {
  140                                 /*
  141                                  * If this is the case, we should be able
  142                                  * to insert ourselves at the head of the
  143                                  * list.  If we can't, something is wrong.
  144                                  */
  145                                 if (ds_tmp == STAILQ_FIRST(devstat_head)) {
  146                                         STAILQ_INSERT_HEAD(devstat_head,
  147                                                            ds, dev_links);
  148                                         break;
  149                                 } else {
  150                                         STAILQ_INSERT_TAIL(devstat_head,
  151                                                            ds, dev_links);
  152                                         printf("devstat_add_entry: HELP! "
  153                                                "sorting problem detected "
  154                                                "for name %p unit %d\n",
  155                                                dev_name, unit_number);
  156                                         break;
  157                                 }
  158                         }
  159                 }
  160         }
  161 
  162         ds->device_number = devstat_current_devnumber++;
  163         ds->unit_number = unit_number;
  164         strlcpy(ds->device_name, dev_name, DEVSTAT_NAME_LEN);
  165         ds->block_size = block_size;
  166         ds->flags = flags;
  167         ds->device_type = device_type;
  168         ds->priority = priority;
  169         binuptime(&ds->creation_time);
  170         devstat_generation++;
  171 }
  172 
  173 /*
  174  * Remove a devstat structure from the list of devices.
  175  */
  176 void
  177 devstat_remove_entry(struct devstat *ds)
  178 {
  179         struct devstatlist *devstat_head;
  180 
  181         mtx_assert(&devstat_mutex, MA_NOTOWNED);
  182         if (ds == NULL)
  183                 return;
  184 
  185         mtx_lock(&devstat_mutex);
  186 
  187         devstat_head = &device_statq;
  188 
  189         /* Remove this entry from the devstat queue */
  190         atomic_add_acq_int(&ds->sequence1, 1);
  191         if (ds->id == NULL) {
  192                 devstat_num_devs--;
  193                 STAILQ_REMOVE(devstat_head, ds, devstat, dev_links);
  194         }
  195         devstat_free(ds);
  196         devstat_generation++;
  197         mtx_unlock(&devstat_mutex);
  198 }
  199 
  200 /*
  201  * Record a transaction start.
  202  *
  203  * See comments for devstat_end_transaction().  Ordering is very important
  204  * here.
  205  */
  206 void
  207 devstat_start_transaction(struct devstat *ds, struct bintime *now)
  208 {
  209 
  210         mtx_assert(&devstat_mutex, MA_NOTOWNED);
  211 
  212         /* sanity check */
  213         if (ds == NULL)
  214                 return;
  215 
  216         atomic_add_acq_int(&ds->sequence1, 1);
  217         /*
  218          * We only want to set the start time when we are going from idle
  219          * to busy.  The start time is really the start of the latest busy
  220          * period.
  221          */
  222         if (ds->start_count == ds->end_count) {
  223                 if (now != NULL)
  224                         ds->busy_from = *now;
  225                 else
  226                         binuptime(&ds->busy_from);
  227         }
  228         ds->start_count++;
  229         atomic_add_rel_int(&ds->sequence0, 1);
  230 }
  231 
  232 void
  233 devstat_start_transaction_bio(struct devstat *ds, struct bio *bp)
  234 {
  235 
  236         mtx_assert(&devstat_mutex, MA_NOTOWNED);
  237 
  238         /* sanity check */
  239         if (ds == NULL)
  240                 return;
  241 
  242         binuptime(&bp->bio_t0);
  243         devstat_start_transaction(ds, &bp->bio_t0);
  244 }
  245 
  246 /*
  247  * Record the ending of a transaction, and incrment the various counters.
  248  *
  249  * Ordering in this function, and in devstat_start_transaction() is VERY
  250  * important.  The idea here is to run without locks, so we are very
  251  * careful to only modify some fields on the way "down" (i.e. at
  252  * transaction start) and some fields on the way "up" (i.e. at transaction
  253  * completion).  One exception is busy_from, which we only modify in
  254  * devstat_start_transaction() when there are no outstanding transactions,
  255  * and thus it can't be modified in devstat_end_transaction()
  256  * simultaneously.
  257  *
  258  * The sequence0 and sequence1 fields are provided to enable an application
  259  * spying on the structures with mmap(2) to tell when a structure is in a
  260  * consistent state or not.
  261  *
  262  * For this to work 100% reliably, it is important that the two fields
  263  * are at opposite ends of the structure and that they are incremented
  264  * in the opposite order of how a memcpy(3) in userland would copy them.
  265  * We assume that the copying happens front to back, but there is actually
  266  * no way short of writing your own memcpy(3) replacement to guarantee
  267  * this will be the case.
  268  *
  269  * In addition to this, being a kind of locks, they must be updated with
  270  * atomic instructions using appropriate memory barriers.
  271  */
  272 void
  273 devstat_end_transaction(struct devstat *ds, uint32_t bytes, 
  274                         devstat_tag_type tag_type, devstat_trans_flags flags,
  275                         struct bintime *now, struct bintime *then)
  276 {
  277         struct bintime dt, lnow;
  278 
  279         /* sanity check */
  280         if (ds == NULL)
  281                 return;
  282 
  283         if (now == NULL) {
  284                 now = &lnow;
  285                 binuptime(now);
  286         }
  287 
  288         atomic_add_acq_int(&ds->sequence1, 1);
  289         /* Update byte and operations counts */
  290         ds->bytes[flags] += bytes;
  291         ds->operations[flags]++;
  292 
  293         /*
  294          * Keep a count of the various tag types sent.
  295          */
  296         if ((ds->flags & DEVSTAT_NO_ORDERED_TAGS) == 0 &&
  297             tag_type != DEVSTAT_TAG_NONE)
  298                 ds->tag_types[tag_type]++;
  299 
  300         if (then != NULL) {
  301                 /* Update duration of operations */
  302                 dt = *now;
  303                 bintime_sub(&dt, then);
  304                 bintime_add(&ds->duration[flags], &dt);
  305         }
  306 
  307         /* Accumulate busy time */
  308         dt = *now;
  309         bintime_sub(&dt, &ds->busy_from);
  310         bintime_add(&ds->busy_time, &dt);
  311         ds->busy_from = *now;
  312 
  313         ds->end_count++;
  314         atomic_add_rel_int(&ds->sequence0, 1);
  315 }
  316 
  317 void
  318 devstat_end_transaction_bio(struct devstat *ds, struct bio *bp)
  319 {
  320         devstat_trans_flags flg;
  321 
  322         /* sanity check */
  323         if (ds == NULL)
  324                 return;
  325 
  326         if (bp->bio_cmd == BIO_DELETE)
  327                 flg = DEVSTAT_FREE;
  328         else if (bp->bio_cmd == BIO_READ)
  329                 flg = DEVSTAT_READ;
  330         else if (bp->bio_cmd == BIO_WRITE)
  331                 flg = DEVSTAT_WRITE;
  332         else 
  333                 flg = DEVSTAT_NO_DATA;
  334 
  335         devstat_end_transaction(ds, bp->bio_bcount - bp->bio_resid,
  336                                 DEVSTAT_TAG_SIMPLE, flg, NULL, &bp->bio_t0);
  337 }
  338 
  339 /*
  340  * This is the sysctl handler for the devstat package.  The data pushed out
  341  * on the kern.devstat.all sysctl variable consists of the current devstat
  342  * generation number, and then an array of devstat structures, one for each
  343  * device in the system.
  344  *
  345  * This is more cryptic that obvious, but basically we neither can nor
  346  * want to hold the devstat_mutex for any amount of time, so we grab it
  347  * only when we need to and keep an eye on devstat_generation all the time.
  348  */
  349 static int
  350 sysctl_devstat(SYSCTL_HANDLER_ARGS)
  351 {
  352         int error;
  353         long mygen;
  354         struct devstat *nds;
  355 
  356         mtx_assert(&devstat_mutex, MA_NOTOWNED);
  357 
  358         /*
  359          * XXX devstat_generation should really be "volatile" but that
  360          * XXX freaks out the sysctl macro below.  The places where we
  361          * XXX change it and inspect it are bracketed in the mutex which
  362          * XXX guarantees us proper write barriers.  I don't belive the
  363          * XXX compiler is allowed to optimize mygen away across calls
  364          * XXX to other functions, so the following is belived to be safe.
  365          */
  366         mygen = devstat_generation;
  367 
  368         error = SYSCTL_OUT(req, &mygen, sizeof(mygen));
  369 
  370         if (devstat_num_devs == 0)
  371                 return(0);
  372 
  373         if (error != 0)
  374                 return (error);
  375 
  376         mtx_lock(&devstat_mutex);
  377         nds = STAILQ_FIRST(&device_statq); 
  378         if (mygen != devstat_generation)
  379                 error = EBUSY;
  380         mtx_unlock(&devstat_mutex);
  381 
  382         if (error != 0)
  383                 return (error);
  384 
  385         for (;nds != NULL;) {
  386                 error = SYSCTL_OUT(req, nds, sizeof(struct devstat));
  387                 if (error != 0)
  388                         return (error);
  389                 mtx_lock(&devstat_mutex);
  390                 if (mygen != devstat_generation)
  391                         error = EBUSY;
  392                 else
  393                         nds = STAILQ_NEXT(nds, dev_links);
  394                 mtx_unlock(&devstat_mutex);
  395                 if (error != 0)
  396                         return (error);
  397         }
  398         return(error);
  399 }
  400 
  401 /*
  402  * Sysctl entries for devstat.  The first one is a node that all the rest
  403  * hang off of. 
  404  */
  405 SYSCTL_NODE(_kern, OID_AUTO, devstat, CTLFLAG_RD, NULL, "Device Statistics");
  406 
  407 SYSCTL_PROC(_kern_devstat, OID_AUTO, all, CTLFLAG_RD|CTLTYPE_OPAQUE,
  408     NULL, 0, sysctl_devstat, "S,devstat", "All devices in the devstat list");
  409 /*
  410  * Export the number of devices in the system so that userland utilities
  411  * can determine how much memory to allocate to hold all the devices.
  412  */
  413 SYSCTL_INT(_kern_devstat, OID_AUTO, numdevs, CTLFLAG_RD, 
  414     &devstat_num_devs, 0, "Number of devices in the devstat list");
  415 SYSCTL_LONG(_kern_devstat, OID_AUTO, generation, CTLFLAG_RD,
  416     &devstat_generation, 0, "Devstat list generation");
  417 SYSCTL_INT(_kern_devstat, OID_AUTO, version, CTLFLAG_RD, 
  418     &devstat_version, 0, "Devstat list version number");
  419 
  420 /*
  421  * Allocator for struct devstat structures.  We sub-allocate these from pages
  422  * which we get from malloc.  These pages are exported for mmap(2)'ing through
  423  * a miniature device driver
  424  */
  425 
  426 #define statsperpage (PAGE_SIZE / sizeof(struct devstat))
  427 
  428 static d_mmap_t devstat_mmap;
  429 
  430 static struct cdevsw devstat_cdevsw = {
  431         .d_version =    D_VERSION,
  432         .d_flags =      D_NEEDGIANT,
  433         .d_mmap =       devstat_mmap,
  434         .d_name =       "devstat",
  435 };
  436 
  437 struct statspage {
  438         TAILQ_ENTRY(statspage)  list;
  439         struct devstat          *stat;
  440         u_int                   nfree;
  441 };
  442 
  443 static TAILQ_HEAD(, statspage)  pagelist = TAILQ_HEAD_INITIALIZER(pagelist);
  444 static MALLOC_DEFINE(M_DEVSTAT, "devstat", "Device statistics");
  445 
  446 static int
  447 devstat_mmap(struct cdev *dev, vm_ooffset_t offset, vm_paddr_t *paddr,
  448     int nprot, vm_memattr_t *memattr)
  449 {
  450         struct statspage *spp;
  451 
  452         if (nprot != VM_PROT_READ)
  453                 return (-1);
  454         TAILQ_FOREACH(spp, &pagelist, list) {
  455                 if (offset == 0) {
  456                         *paddr = vtophys(spp->stat);
  457                         return (0);
  458                 }
  459                 offset -= PAGE_SIZE;
  460         }
  461         return (-1);
  462 }
  463 
  464 static struct devstat *
  465 devstat_alloc(void)
  466 {
  467         struct devstat *dsp;
  468         struct statspage *spp, *spp2;
  469         u_int u;
  470         static int once;
  471 
  472         mtx_assert(&devstat_mutex, MA_NOTOWNED);
  473         if (!once) {
  474                 make_dev_credf(MAKEDEV_ETERNAL | MAKEDEV_CHECKNAME,
  475                     &devstat_cdevsw, 0, NULL, UID_ROOT, GID_WHEEL, 0400,
  476                     DEVSTAT_DEVICE_NAME);
  477                 once = 1;
  478         }
  479         spp2 = NULL;
  480         mtx_lock(&devstat_mutex);
  481         for (;;) {
  482                 TAILQ_FOREACH(spp, &pagelist, list) {
  483                         if (spp->nfree > 0)
  484                                 break;
  485                 }
  486                 if (spp != NULL)
  487                         break;
  488                 mtx_unlock(&devstat_mutex);
  489                 spp2 = malloc(sizeof *spp, M_DEVSTAT, M_ZERO | M_WAITOK);
  490                 spp2->stat = malloc(PAGE_SIZE, M_DEVSTAT, M_ZERO | M_WAITOK);
  491                 spp2->nfree = statsperpage;
  492 
  493                 /*
  494                  * If free statspages were added while the lock was released
  495                  * just reuse them.
  496                  */
  497                 mtx_lock(&devstat_mutex);
  498                 TAILQ_FOREACH(spp, &pagelist, list)
  499                         if (spp->nfree > 0)
  500                                 break;
  501                 if (spp == NULL) {
  502                         spp = spp2;
  503 
  504                         /*
  505                          * It would make more sense to add the new page at the
  506                          * head but the order on the list determine the
  507                          * sequence of the mapping so we can't do that.
  508                          */
  509                         TAILQ_INSERT_TAIL(&pagelist, spp, list);
  510                 } else
  511                         break;
  512         }
  513         dsp = spp->stat;
  514         for (u = 0; u < statsperpage; u++) {
  515                 if (dsp->allocated == 0)
  516                         break;
  517                 dsp++;
  518         }
  519         spp->nfree--;
  520         dsp->allocated = 1;
  521         mtx_unlock(&devstat_mutex);
  522         if (spp2 != NULL && spp2 != spp) {
  523                 free(spp2->stat, M_DEVSTAT);
  524                 free(spp2, M_DEVSTAT);
  525         }
  526         return (dsp);
  527 }
  528 
  529 static void
  530 devstat_free(struct devstat *dsp)
  531 {
  532         struct statspage *spp;
  533 
  534         mtx_assert(&devstat_mutex, MA_OWNED);
  535         bzero(dsp, sizeof *dsp);
  536         TAILQ_FOREACH(spp, &pagelist, list) {
  537                 if (dsp >= spp->stat && dsp < (spp->stat + statsperpage)) {
  538                         spp->nfree++;
  539                         return;
  540                 }
  541         }
  542 }
  543 
  544 SYSCTL_INT(_debug_sizeof, OID_AUTO, devstat, CTLFLAG_RD,
  545     NULL, sizeof(struct devstat), "sizeof(struct devstat)");

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