Date: Thu, 3 Dec 2009 21:50:03 GMT From: dfilter@FreeBSD.ORG (dfilter service) To: freebsd-geom@FreeBSD.org Subject: Re: kern/113885: commit references a PR Message-ID: <200912032150.nB3Lo3lG013858@freefall.freebsd.org>
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The following reply was made to PR kern/113885; it has been noted by GNATS. From: dfilter@FreeBSD.ORG (dfilter service) To: bug-followup@FreeBSD.org Cc: Subject: Re: kern/113885: commit references a PR Date: Thu, 3 Dec 2009 21:48:01 +0000 (UTC) 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. */ _______________________________________________ svn-src-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscribe@freebsd.org"
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