subr_devstat.c

Go to the documentation of this file.

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1997, 1998, 1999 Kenneth D. Merry.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
 
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
 
#include <sys/param.h>
#include <sys/disk.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/bio.h>
#include <sys/devicestat.h>
#include <sys/sdt.h>
#include <sys/sysctl.h>
#include <sys/malloc.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/conf.h>
#include <vm/vm.h>
#include <vm/pmap.h>
 
#include <machine/atomic.h>
 
SDT_PROVIDER_DEFINE(io);
 
SDT_PROBE_DEFINE2(io, , , start, "struct bio *", "struct devstat *");
SDT_PROBE_DEFINE2(io, , , done, "struct bio *", "struct devstat *");
SDT_PROBE_DEFINE2(io, , , wait__start, "struct bio *",
    "struct devstat *");
SDT_PROBE_DEFINE2(io, , , wait__done, "struct bio *",
    "struct devstat *");
 
#define DTRACE_DEVSTAT_START()          SDT_PROBE2(io, , , start, NULL, ds)
#define DTRACE_DEVSTAT_BIO_START()      SDT_PROBE2(io, , , start, bp, ds)
#define DTRACE_DEVSTAT_DONE()           SDT_PROBE2(io, , , done, NULL, ds)
#define DTRACE_DEVSTAT_BIO_DONE()       SDT_PROBE2(io, , , done, bp, ds)
#define DTRACE_DEVSTAT_WAIT_START()     SDT_PROBE2(io, , , wait__start, NULL, ds)
#define DTRACE_DEVSTAT_WAIT_DONE()      SDT_PROBE2(io, , , wait__done, NULL, ds)
 
static int devstat_num_devs;
static long devstat_generation = 1;
static int devstat_version = DEVSTAT_VERSION;
static int devstat_current_devnumber;
static struct mtx devstat_mutex;
MTX_SYSINIT(devstat_mutex, &devstat_mutex, "devstat", MTX_DEF);
 
static struct devstatlist device_statq = STAILQ_HEAD_INITIALIZER(device_statq);
static struct devstat *devstat_alloc(void);
static void devstat_free(struct devstat *);
static void devstat_add_entry(struct devstat *ds, const void *dev_name, 
                       int unit_number, uint32_t block_size,
                       devstat_support_flags flags,
                       devstat_type_flags device_type,
                       devstat_priority priority);
 
/*
 * Allocate a devstat and initialize it
 */
struct devstat *
devstat_new_entry(const void *dev_name,
                  int unit_number, uint32_t block_size,
                  devstat_support_flags flags,
                  devstat_type_flags device_type,
                  devstat_priority priority)
{
        struct devstat *ds;
 
        mtx_assert(&devstat_mutex, MA_NOTOWNED);
 
        ds = devstat_alloc();
        mtx_lock(&devstat_mutex);
        if (unit_number == -1) {
                ds->unit_number = unit_number;
                ds->id = dev_name;
                binuptime(&ds->creation_time);
                devstat_generation++;
        } else {
                devstat_add_entry(ds, dev_name, unit_number, block_size,
                                  flags, device_type, priority);
        }
        mtx_unlock(&devstat_mutex);
        return (ds);
}
 
/*
 * Take a malloced and zeroed devstat structure given to us, fill it in 
 * and add it to the queue of devices.  
 */
static void
devstat_add_entry(struct devstat *ds, const void *dev_name, 
                  int unit_number, uint32_t block_size,
                  devstat_support_flags flags,
                  devstat_type_flags device_type,
                  devstat_priority priority)
{
        struct devstatlist *devstat_head;
        struct devstat *ds_tmp;
 
        mtx_assert(&devstat_mutex, MA_OWNED);
        devstat_num_devs++;
 
        devstat_head = &device_statq;
 
        /*
         * Priority sort.  Each driver passes in its priority when it adds
         * its devstat entry.  Drivers are sorted first by priority, and
         * then by probe order.
         * 
         * For the first device, we just insert it, since the priority
         * doesn't really matter yet.  Subsequent devices are inserted into
         * the list using the order outlined above.
         */
        if (devstat_num_devs == 1)
                STAILQ_INSERT_TAIL(devstat_head, ds, dev_links);
        else {
                STAILQ_FOREACH(ds_tmp, devstat_head, dev_links) {
                        struct devstat *ds_next;
 
                        ds_next = STAILQ_NEXT(ds_tmp, dev_links);
 
                        /*
                         * If we find a break between higher and lower
                         * priority items, and if this item fits in the
                         * break, insert it.  This also applies if the
                         * "lower priority item" is the end of the list.
                         */
                        if ((priority <= ds_tmp->priority)
                         && ((ds_next == NULL)
                           || (priority > ds_next->priority))) {
                                STAILQ_INSERT_AFTER(devstat_head, ds_tmp, ds,
                                                    dev_links);
                                break;
                        } else if (priority > ds_tmp->priority) {
                                /*
                                 * If this is the case, we should be able
                                 * to insert ourselves at the head of the
                                 * list.  If we can't, something is wrong.
                                 */
                                if (ds_tmp == STAILQ_FIRST(devstat_head)) {
                                        STAILQ_INSERT_HEAD(devstat_head,
                                                           ds, dev_links);
                                        break;
                                } else {
                                        STAILQ_INSERT_TAIL(devstat_head,
                                                           ds, dev_links);
                                        printf("devstat_add_entry: HELP! "
                                               "sorting problem detected "
                                               "for name %p unit %d\n",
                                               dev_name, unit_number);
                                        break;
                                }
                        }
                }
        }
 
        ds->device_number = devstat_current_devnumber++;
        ds->unit_number = unit_number;
        strlcpy(ds->device_name, dev_name, DEVSTAT_NAME_LEN);
        ds->block_size = block_size;
        ds->flags = flags;
        ds->device_type = device_type;
        ds->priority = priority;
        binuptime(&ds->creation_time);
        devstat_generation++;
}
 
/*
 * Remove a devstat structure from the list of devices.
 */
void
devstat_remove_entry(struct devstat *ds)
{
        struct devstatlist *devstat_head;
 
        mtx_assert(&devstat_mutex, MA_NOTOWNED);
        if (ds == NULL)
                return;
 
        mtx_lock(&devstat_mutex);
 
        devstat_head = &device_statq;
 
        /* Remove this entry from the devstat queue */
        atomic_add_acq_int(&ds->sequence1, 1);
        if (ds->unit_number != -1) {
                devstat_num_devs--;
                STAILQ_REMOVE(devstat_head, ds, devstat, dev_links);
        }
        devstat_free(ds);
        devstat_generation++;
        mtx_unlock(&devstat_mutex);
}
 
/*
 * Record a transaction start.
 *
 * See comments for devstat_end_transaction().  Ordering is very important
 * here.
 */
void
devstat_start_transaction(struct devstat *ds, const struct bintime *now)
{
 
        /* sanity check */
        if (ds == NULL)
                return;
 
        atomic_add_acq_int(&ds->sequence1, 1);
        /*
         * We only want to set the start time when we are going from idle
         * to busy.  The start time is really the start of the latest busy
         * period.
         */
        if (atomic_fetchadd_int(&ds->start_count, 1) == ds->end_count) {
                if (now != NULL)
                        ds->busy_from = *now;
                else
                        binuptime(&ds->busy_from);
        }
        atomic_add_rel_int(&ds->sequence0, 1);
        DTRACE_DEVSTAT_START();
}
 
void
devstat_start_transaction_bio(struct devstat *ds, struct bio *bp)
{
 
        /* sanity check */
        if (ds == NULL)
                return;
 
        binuptime(&bp->bio_t0);
        devstat_start_transaction_bio_t0(ds, bp);
}
 
void
devstat_start_transaction_bio_t0(struct devstat *ds, struct bio *bp)
{
 
        /* sanity check */
        if (ds == NULL)
                return;
 
        devstat_start_transaction(ds, &bp->bio_t0);
        DTRACE_DEVSTAT_BIO_START();
}
 
/*
 * Record the ending of a transaction, and incrment the various counters.
 *
 * Ordering in this function, and in devstat_start_transaction() is VERY
 * important.  The idea here is to run without locks, so we are very
 * careful to only modify some fields on the way "down" (i.e. at
 * transaction start) and some fields on the way "up" (i.e. at transaction
 * completion).  One exception is busy_from, which we only modify in
 * devstat_start_transaction() when there are no outstanding transactions,
 * and thus it can't be modified in devstat_end_transaction()
 * simultaneously.
 *
 * The sequence0 and sequence1 fields are provided to enable an application
 * spying on the structures with mmap(2) to tell when a structure is in a
 * consistent state or not.
 *
 * For this to work 100% reliably, it is important that the two fields
 * are at opposite ends of the structure and that they are incremented
 * in the opposite order of how a memcpy(3) in userland would copy them.
 * We assume that the copying happens front to back, but there is actually
 * no way short of writing your own memcpy(3) replacement to guarantee
 * this will be the case.
 *
 * In addition to this, being a kind of locks, they must be updated with
 * atomic instructions using appropriate memory barriers.
 */
void
devstat_end_transaction(struct devstat *ds, uint32_t bytes, 
                        devstat_tag_type tag_type, devstat_trans_flags flags,
                        const struct bintime *now, const struct bintime *then)
{
        struct bintime dt, lnow;
 
        /* sanity check */
        if (ds == NULL)
                return;
 
        if (now == NULL) {
                binuptime(&lnow);
                now = &lnow;
        }
 
        atomic_add_acq_int(&ds->sequence1, 1);
        /* Update byte and operations counts */
        ds->bytes[flags] += bytes;
        ds->operations[flags]++;
 
        /*
         * Keep a count of the various tag types sent.
         */
        if ((ds->flags & DEVSTAT_NO_ORDERED_TAGS) == 0 &&
            tag_type != DEVSTAT_TAG_NONE)
                ds->tag_types[tag_type]++;
 
        if (then != NULL) {
                /* Update duration of operations */
                dt = *now;
                bintime_sub(&dt, then);
                bintime_add(&ds->duration[flags], &dt);
        }
 
        /* Accumulate busy time */
        dt = *now;
        bintime_sub(&dt, &ds->busy_from);
        bintime_add(&ds->busy_time, &dt);
        ds->busy_from = *now;
 
        ds->end_count++;
        atomic_add_rel_int(&ds->sequence0, 1);
        DTRACE_DEVSTAT_DONE();
}
 
void
devstat_end_transaction_bio(struct devstat *ds, const struct bio *bp)
{
 
        devstat_end_transaction_bio_bt(ds, bp, NULL);
}
 
void
devstat_end_transaction_bio_bt(struct devstat *ds, const struct bio *bp,
    const struct bintime *now)
{
        devstat_trans_flags flg;
        devstat_tag_type tag;
 
        /* sanity check */
        if (ds == NULL)
                return;
 
        if (bp->bio_flags & BIO_ORDERED)
                tag = DEVSTAT_TAG_ORDERED;
        else
                tag = DEVSTAT_TAG_SIMPLE;
        if (bp->bio_cmd == BIO_DELETE)
                flg = DEVSTAT_FREE;
        else if ((bp->bio_cmd == BIO_READ)
              || ((bp->bio_cmd == BIO_ZONE)
               && (bp->bio_zone.zone_cmd == DISK_ZONE_REPORT_ZONES)))
                flg = DEVSTAT_READ;
        else if (bp->bio_cmd == BIO_WRITE)
                flg = DEVSTAT_WRITE;
        else 
                flg = DEVSTAT_NO_DATA;
 
        devstat_end_transaction(ds, bp->bio_bcount - bp->bio_resid,
                                tag, flg, now, &bp->bio_t0);
        DTRACE_DEVSTAT_BIO_DONE();
}
 
/*
 * This is the sysctl handler for the devstat package.  The data pushed out
 * on the kern.devstat.all sysctl variable consists of the current devstat
 * generation number, and then an array of devstat structures, one for each
 * device in the system.
 *
 * This is more cryptic that obvious, but basically we neither can nor
 * want to hold the devstat_mutex for any amount of time, so we grab it
 * only when we need to and keep an eye on devstat_generation all the time.
 */
static int
sysctl_devstat(SYSCTL_HANDLER_ARGS)
{
        int error;
        long mygen;
        struct devstat *nds;
 
        mtx_assert(&devstat_mutex, MA_NOTOWNED);
 
        /*
         * XXX devstat_generation should really be "volatile" but that
         * XXX freaks out the sysctl macro below.  The places where we
         * XXX change it and inspect it are bracketed in the mutex which
         * XXX guarantees us proper write barriers.  I don't believe the
         * XXX compiler is allowed to optimize mygen away across calls
         * XXX to other functions, so the following is belived to be safe.
         */
        mygen = devstat_generation;
 
        error = SYSCTL_OUT(req, &mygen, sizeof(mygen));
 
        if (devstat_num_devs == 0)
                return(0);
 
        if (error != 0)
                return (error);
 
        mtx_lock(&devstat_mutex);
        nds = STAILQ_FIRST(&device_statq); 
        if (mygen != devstat_generation)
                error = EBUSY;
        mtx_unlock(&devstat_mutex);
 
        if (error != 0)
                return (error);
 
        for (;nds != NULL;) {
                error = SYSCTL_OUT(req, nds, sizeof(struct devstat));
                if (error != 0)
                        return (error);
                mtx_lock(&devstat_mutex);
                if (mygen != devstat_generation)
                        error = EBUSY;
                else
                        nds = STAILQ_NEXT(nds, dev_links);
                mtx_unlock(&devstat_mutex);
                if (error != 0)
                        return (error);
        }
        return(error);
}
 
/*
 * Sysctl entries for devstat.  The first one is a node that all the rest
 * hang off of. 
 */
static SYSCTL_NODE(_kern, OID_AUTO, devstat, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL,
    "Device Statistics");
 
SYSCTL_PROC(_kern_devstat, OID_AUTO, all,
    CTLFLAG_RD | CTLTYPE_OPAQUE | CTLFLAG_MPSAFE, NULL, 0,
    sysctl_devstat, "S,devstat",
    "All devices in the devstat list");
/*
 * Export the number of devices in the system so that userland utilities
 * can determine how much memory to allocate to hold all the devices.
 */
SYSCTL_INT(_kern_devstat, OID_AUTO, numdevs, CTLFLAG_RD, 
    &devstat_num_devs, 0, "Number of devices in the devstat list");
SYSCTL_LONG(_kern_devstat, OID_AUTO, generation, CTLFLAG_RD,
    &devstat_generation, 0, "Devstat list generation");
SYSCTL_INT(_kern_devstat, OID_AUTO, version, CTLFLAG_RD, 
    &devstat_version, 0, "Devstat list version number");
 
/*
 * Allocator for struct devstat structures.  We sub-allocate these from pages
 * which we get from malloc.  These pages are exported for mmap(2)'ing through
 * a miniature device driver
 */
 
#define statsperpage (PAGE_SIZE / sizeof(struct devstat))
 
static d_ioctl_t devstat_ioctl;
static d_mmap_t devstat_mmap;
 
static struct cdevsw devstat_cdevsw = {
        .d_version =    D_VERSION,
        .d_ioctl =      devstat_ioctl,
        .d_mmap =       devstat_mmap,
        .d_name =       "devstat",
};
 
struct statspage {
        TAILQ_ENTRY(statspage)  list;
        struct devstat          *stat;
        u_int                   nfree;
};
 
static size_t pagelist_pages = 0;
static TAILQ_HEAD(, statspage)  pagelist = TAILQ_HEAD_INITIALIZER(pagelist);
static MALLOC_DEFINE(M_DEVSTAT, "devstat", "Device statistics");
 
static int
devstat_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int fflag,
    struct thread *td)
{
        int error = ENOTTY;
 
        switch (cmd) {
        case DIOCGMEDIASIZE:
                error = 0;
                *(off_t *)data = pagelist_pages * PAGE_SIZE;
                break;
        }
 
        return (error);
}
 
static int
devstat_mmap(struct cdev *dev, vm_ooffset_t offset, vm_paddr_t *paddr,
    int nprot, vm_memattr_t *memattr)
{
        struct statspage *spp;
 
        if (nprot != VM_PROT_READ)
                return (-1);
        mtx_lock(&devstat_mutex);
        TAILQ_FOREACH(spp, &pagelist, list) {
                if (offset == 0) {
                        *paddr = vtophys(spp->stat);
                        mtx_unlock(&devstat_mutex);
                        return (0);
                }
                offset -= PAGE_SIZE;
        }
        mtx_unlock(&devstat_mutex);
        return (-1);
}
 
static struct devstat *
devstat_alloc(void)
{
        struct devstat *dsp;
        struct statspage *spp, *spp2;
        u_int u;
        static int once;
 
        mtx_assert(&devstat_mutex, MA_NOTOWNED);
        if (!once) {
                make_dev_credf(MAKEDEV_ETERNAL | MAKEDEV_CHECKNAME,
                    &devstat_cdevsw, 0, NULL, UID_ROOT, GID_WHEEL, 0444,
                    DEVSTAT_DEVICE_NAME);
                once = 1;
        }
        spp2 = NULL;
        mtx_lock(&devstat_mutex);
        for (;;) {
                TAILQ_FOREACH(spp, &pagelist, list) {
                        if (spp->nfree > 0)
                                break;
                }
                if (spp != NULL)
                        break;
                mtx_unlock(&devstat_mutex);
                spp2 = malloc(sizeof *spp, M_DEVSTAT, M_ZERO | M_WAITOK);
                spp2->stat = malloc(PAGE_SIZE, M_DEVSTAT, M_ZERO | M_WAITOK);
                spp2->nfree = statsperpage;
 
                /*
                 * If free statspages were added while the lock was released
                 * just reuse them.
                 */
                mtx_lock(&devstat_mutex);
                TAILQ_FOREACH(spp, &pagelist, list)
                        if (spp->nfree > 0)
                                break;
                if (spp == NULL) {
                        spp = spp2;
 
                        /*
                         * It would make more sense to add the new page at the
                         * head but the order on the list determine the
                         * sequence of the mapping so we can't do that.
                         */
                        pagelist_pages++;
                        TAILQ_INSERT_TAIL(&pagelist, spp, list);
                } else
                        break;
        }
        dsp = spp->stat;
        for (u = 0; u < statsperpage; u++) {
                if (dsp->allocated == 0)
                        break;
                dsp++;
        }
        spp->nfree--;
        dsp->allocated = 1;
        mtx_unlock(&devstat_mutex);
        if (spp2 != NULL && spp2 != spp) {
                free(spp2->stat, M_DEVSTAT);
                free(spp2, M_DEVSTAT);
        }
        return (dsp);
}
 
static void
devstat_free(struct devstat *dsp)
{
        struct statspage *spp;
 
        mtx_assert(&devstat_mutex, MA_OWNED);
        bzero(dsp, sizeof *dsp);
        TAILQ_FOREACH(spp, &pagelist, list) {
                if (dsp >= spp->stat && dsp < (spp->stat + statsperpage)) {
                        spp->nfree++;
                        return;
                }
        }
}
 
SYSCTL_INT(_debug_sizeof, OID_AUTO, devstat, CTLFLAG_RD,
    SYSCTL_NULL_INT_PTR, sizeof(struct devstat), "sizeof(struct devstat)");