FreeBSD-5.3/sys/kern/subr_devstat.c
/*
* 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: src/sys/kern/subr_devstat.c,v 1.49 2004/06/16 09:47:12 phk Exp $");
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/bio.h>
#include <sys/devicestat.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>
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;
static struct devstatlist 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, u_int32_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, u_int32_t block_size,
devstat_support_flags flags,
devstat_type_flags device_type,
devstat_priority priority)
{
struct devstat *ds;
static int once;
if (!once) {
STAILQ_INIT(&device_statq);
mtx_init(&devstat_mutex, "devstat", NULL, MTX_DEF);
once = 1;
}
mtx_assert(&devstat_mutex, MA_NOTOWNED);
ds = devstat_alloc();
mtx_lock(&devstat_mutex);
if (unit_number == -1) {
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, u_int32_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->id == NULL) {
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, struct bintime *now)
{
mtx_assert(&devstat_mutex, MA_NOTOWNED);
/* 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 (ds->start_count == ds->end_count) {
if (now != NULL)
ds->busy_from = *now;
else
binuptime(&ds->busy_from);
}
ds->start_count++;
atomic_add_rel_int(&ds->sequence0, 1);
}
void
devstat_start_transaction_bio(struct devstat *ds, struct bio *bp)
{
mtx_assert(&devstat_mutex, MA_NOTOWNED);
/* sanity check */
if (ds == NULL)
return;
binuptime(&bp->bio_t0);
devstat_start_transaction(ds, &bp->bio_t0);
}
/*
* 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, u_int32_t bytes,
devstat_tag_type tag_type, devstat_trans_flags flags,
struct bintime *now, struct bintime *then)
{
struct bintime dt, lnow;
mtx_assert(&devstat_mutex, MA_NOTOWNED);
/* sanity check */
if (ds == NULL)
return;
if (now == NULL) {
now = &lnow;
binuptime(now);
}
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);
}
void
devstat_end_transaction_bio(struct devstat *ds, struct bio *bp)
{
devstat_trans_flags flg;
mtx_assert(&devstat_mutex, MA_NOTOWNED);
/* sanity check */
if (ds == NULL)
return;
if (bp->bio_cmd == BIO_DELETE)
flg = DEVSTAT_FREE;
else if (bp->bio_cmd == BIO_READ)
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,
DEVSTAT_TAG_SIMPLE, flg, NULL, &bp->bio_t0);
}
/*
* 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 belive 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.
*/
SYSCTL_NODE(_kern, OID_AUTO, devstat, CTLFLAG_RD, 0, "Device Statistics");
SYSCTL_PROC(_kern_devstat, OID_AUTO, all, CTLFLAG_RD|CTLTYPE_OPAQUE,
0, 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_mmap_t devstat_mmap;
static struct cdevsw devstat_cdevsw = {
.d_version = D_VERSION,
.d_flags = D_NEEDGIANT,
.d_mmap = devstat_mmap,
.d_name = "devstat",
};
struct statspage {
TAILQ_ENTRY(statspage) list;
struct devstat *stat;
u_int nfree;
};
static TAILQ_HEAD(, statspage) pagelist = TAILQ_HEAD_INITIALIZER(pagelist);
static MALLOC_DEFINE(M_DEVSTAT, "devstat", "Device statistics");
static int
devstat_mmap(struct cdev *dev, vm_offset_t offset, vm_paddr_t *paddr, int nprot)
{
struct statspage *spp;
if (nprot != VM_PROT_READ)
return (-1);
TAILQ_FOREACH(spp, &pagelist, list) {
if (offset == 0) {
*paddr = vtophys(spp->stat);
return (0);
}
offset -= PAGE_SIZE;
}
return (-1);
}
static struct devstat *
devstat_alloc(void)
{
struct devstat *dsp;
struct statspage *spp;
u_int u;
static int once;
mtx_assert(&devstat_mutex, MA_NOTOWNED);
if (!once) {
make_dev(&devstat_cdevsw, 0,
UID_ROOT, GID_WHEEL, 0400, DEVSTAT_DEVICE_NAME);
once = 1;
}
mtx_lock(&devstat_mutex);
for (;;) {
TAILQ_FOREACH(spp, &pagelist, list) {
if (spp->nfree > 0)
break;
}
if (spp != NULL)
break;
/*
* We had no free slot in any of our pages, drop the mutex
* and get another page. In theory we could have more than
* one process doing this at the same time and consequently
* we may allocate more pages than we will need. That is
* Just Too Bad[tm], we can live with that.
*/
mtx_unlock(&devstat_mutex);
spp = malloc(sizeof *spp, M_DEVSTAT, M_ZERO | M_WAITOK);
spp->stat = malloc(PAGE_SIZE, M_DEVSTAT, M_ZERO | M_WAITOK);
spp->nfree = statsperpage;
mtx_lock(&devstat_mutex);
/*
* 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.
*/
TAILQ_INSERT_TAIL(&pagelist, spp, list);
}
dsp = spp->stat;
for (u = 0; u < statsperpage; u++) {
if (dsp->allocated == 0)
break;
dsp++;
}
spp->nfree--;
dsp->allocated = 1;
mtx_unlock(&devstat_mutex);
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,
0, sizeof(struct devstat), "sizeof(struct devstat)");