2009/12/15 Wiktor Niesiobedzki <b...@w.evip.pl>: > 2009/12/15 Ivan Voras <ivo...@freebsd.org>: >> The context of this post is file servers running FreeBSD 8 and ZFS with >> compressed file systems on low-end hardware, or actually high-end hardware >> on VMWare ESX 3.5 and 4, which kind of makes it low-end as far as storage is >> concerned. The servers are standby backup mirrors of production servers - >> thus many writes, few reads. >> >> Running this setup I notice two things: >> >> 1) load averages get very high, though the only usage these systems get is >> file system usage: >> 2) long pauses, in what looks like vfs.zfs.txg.timeout second intervals, >> which seemengly block everything, or at least the entire userland. These >> pauses are sometimes so long that file transfers fail, which must be >> avoided. >> >> Looking at the list of processes it looks like a large number of kernel and >> userland processes are woken up at once. From the kernel side there are >> regularily all g_* threads, but also unrelated threads like bufdaemon, >> softdepflush, etc. and from the userland - top, syslog, cron, etc. It is >> like ZFS livelocks everything else. >> >> Any ideas on the "pauses" issue? >> > > Hi, > > I've a bit striped your post. It's kind of "me too" message (more > details here: > http://lists.freebsd.org/pipermail/freebsd-geom/2009-December/003810.html). > What I've figured out so far is, that lowering the kernel thread > priority (as pjd@ suggested) gives quite promising results (no > livelocks at all). Though my bottleneck were caused by GELI thread. > > The pattern there is like this: > > sched_prio(curthread, PRIBIO); > [...] > msleep(sc, &sc->sc_queue_mtx, PDROP | PRIBIO, "geli:w", 0);
I have tried before reducing priority of ZFS taskqueues but only to PRIBIO, not below it - not much effect wrt "pauses". _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
