svn commit: r200086 - head/sys/geom/mirror
Alexander Motin
mav at FreeBSD.org
Thu Dec 3 21:47:51 UTC 2009
Author: mav
Date: Thu Dec 3 21:47:51 2009
New Revision: 200086
URL: http://svn.freebsd.org/changeset/base/200086
Log:
Change 'load' balancing mode algorithm:
- Instead of measuring last request execution time for each drive and
choosing one with smallest time, use averaged number of requests, running
on each drive. This information is more accurate and timely. It allows to
distribute load between drives in more even and predictable way.
- For each drive track offset of the last submitted request. If new request
offset matches previous one or close for some drive, prefer that drive.
It allows to significantly speedup simultaneous sequential reads.
PR: kern/113885
Reviewed by: sobomax
Modified:
head/sys/geom/mirror/g_mirror.c
head/sys/geom/mirror/g_mirror.h
Modified: head/sys/geom/mirror/g_mirror.c
==============================================================================
--- head/sys/geom/mirror/g_mirror.c Thu Dec 3 21:44:41 2009 (r200085)
+++ head/sys/geom/mirror/g_mirror.c Thu Dec 3 21:47:51 2009 (r200086)
@@ -451,9 +451,6 @@ g_mirror_init_disk(struct g_mirror_softc
disk->d_id = md->md_did;
disk->d_state = G_MIRROR_DISK_STATE_NONE;
disk->d_priority = md->md_priority;
- disk->d_delay.sec = 0;
- disk->d_delay.frac = 0;
- binuptime(&disk->d_last_used);
disk->d_flags = md->md_dflags;
if (md->md_provider[0] != '\0')
disk->d_flags |= G_MIRROR_DISK_FLAG_HARDCODED;
@@ -863,16 +860,6 @@ bintime_cmp(struct bintime *bt1, struct
}
static void
-g_mirror_update_delay(struct g_mirror_disk *disk, struct bio *bp)
-{
-
- if (disk->d_softc->sc_balance != G_MIRROR_BALANCE_LOAD)
- return;
- binuptime(&disk->d_delay);
- bintime_sub(&disk->d_delay, &bp->bio_t0);
-}
-
-static void
g_mirror_done(struct bio *bp)
{
struct g_mirror_softc *sc;
@@ -904,8 +891,6 @@ g_mirror_regular_request(struct bio *bp)
g_topology_lock();
g_mirror_kill_consumer(sc, bp->bio_from);
g_topology_unlock();
- } else {
- g_mirror_update_delay(disk, bp);
}
pbp->bio_inbed++;
@@ -1465,30 +1450,35 @@ g_mirror_request_round_robin(struct g_mi
g_io_request(cbp, cp);
}
+#define TRACK_SIZE (1 * 1024 * 1024)
+#define LOAD_SCALE 256
+#define ABS(x) (((x) >= 0) ? (x) : (-(x)))
+
static void
g_mirror_request_load(struct g_mirror_softc *sc, struct bio *bp)
{
struct g_mirror_disk *disk, *dp;
struct g_consumer *cp;
struct bio *cbp;
- struct bintime curtime;
+ int prio, best;
- binuptime(&curtime);
- /*
- * Find a disk which the smallest load.
- */
+ /* Find a disk with the smallest load. */
disk = NULL;
+ best = INT_MAX;
LIST_FOREACH(dp, &sc->sc_disks, d_next) {
if (dp->d_state != G_MIRROR_DISK_STATE_ACTIVE)
continue;
- /* If disk wasn't used for more than 2 sec, use it. */
- if (curtime.sec - dp->d_last_used.sec >= 2) {
- disk = dp;
- break;
- }
- if (disk == NULL ||
- bintime_cmp(&dp->d_delay, &disk->d_delay) < 0) {
+ prio = dp->load;
+ /* If disk head is precisely in position - highly prefer it. */
+ if (dp->d_last_offset == bp->bio_offset)
+ prio -= 2 * LOAD_SCALE;
+ else
+ /* If disk head is close to position - prefer it. */
+ if (ABS(dp->d_last_offset - bp->bio_offset) < TRACK_SIZE)
+ prio -= 1 * LOAD_SCALE;
+ if (prio <= best) {
disk = dp;
+ best = prio;
}
}
KASSERT(disk != NULL, ("NULL disk for %s.", sc->sc_name));
@@ -1505,12 +1495,18 @@ g_mirror_request_load(struct g_mirror_so
cp = disk->d_consumer;
cbp->bio_done = g_mirror_done;
cbp->bio_to = cp->provider;
- binuptime(&disk->d_last_used);
G_MIRROR_LOGREQ(3, cbp, "Sending request.");
KASSERT(cp->acr >= 1 && cp->acw >= 1 && cp->ace >= 1,
("Consumer %s not opened (r%dw%de%d).", cp->provider->name, cp->acr,
cp->acw, cp->ace));
cp->index++;
+ /* Remember last head position */
+ disk->d_last_offset = bp->bio_offset + bp->bio_length;
+ /* Update loads. */
+ LIST_FOREACH(dp, &sc->sc_disks, d_next) {
+ dp->load = (dp->d_consumer->index * LOAD_SCALE +
+ dp->load * 7) / 8;
+ }
g_io_request(cbp, cp);
}
Modified: head/sys/geom/mirror/g_mirror.h
==============================================================================
--- head/sys/geom/mirror/g_mirror.h Thu Dec 3 21:44:41 2009 (r200085)
+++ head/sys/geom/mirror/g_mirror.h Thu Dec 3 21:47:51 2009 (r200086)
@@ -133,8 +133,8 @@ struct g_mirror_disk {
struct g_mirror_softc *d_softc; /* Back-pointer to softc. */
int d_state; /* Disk state. */
u_int d_priority; /* Disk priority. */
- struct bintime d_delay; /* Disk delay. */
- struct bintime d_last_used; /* When disk was last used. */
+ u_int load; /* Averaged queue length */
+ off_t d_last_offset; /* Last read offset */
uint64_t d_flags; /* Additional flags. */
u_int d_genid; /* Disk's generation ID. */
struct g_mirror_disk_sync d_sync;/* Sync information. */
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