Date: Wed, 14 Jul 2010 09:16:09 +0200 From: Martin Matuska <mm@FreeBSD.org> To: Peter Jeremy <peterjeremy@acm.org> Cc: freebsd-current@FreeBSD.org Subject: Re: [CFT] ZFS v15 patch (version 3) Message-ID: <4C3D6439.3010702@FreeBSD.org> In-Reply-To: <20100714001423.GA92530@server.vk2pj.dyndns.org> References: <4C31C71C.2010606@FreeBSD.org> <20100708200446.GA33822@server.vk2pj.dyndns.org> <4C364379.6020608@FreeBSD.org> <20100714001423.GA92530@server.vk2pj.dyndns.org>
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Without head-12636.patch you are unable to reproduce the deadlock? Dňa 14. 7. 2010 2:14, Peter Jeremy wrote / napísal(a): > On 2010-Jul-08 23:30:33 +0200, Martin Matuska <mm@FreeBSD.org> wrote: >> On 8. 7. 2010 22:04, Peter Jeremy wrote / napísal(a): >>> Without patching arc_memory_throttle(), a system behaves especially >>> poorly if it uses ZFS with any of mmap(2), UFS or NFS client - in my >>> case, ports/mail/mairix was almost guaranteed to wedge the system. >>> This is the problem that the following hack is intended to work around: >>> perl -e '$x = "x" x 1000000;' >>> >>> >> Regarding ARC, you might want to try the revision 209227 from head that >> is scheduled for MFC on 18.7.2010: >> http://people.freebsd.org/~mm/patches/zfs/head-12636.patch > I have done some testing with 8-STABLE with head-12636.patch and have > managed to successfully reproduce a deadlock. The system is amd64 > with 2GB RAM running a mixed UFS+ZFS environment. On a freshly booted > system, I unmount/remount my ZFS /home and a UFS scratch filesystem > that contains a 1.5GB file [ensuring there is no cached data from > either FS]. I then dd(1) the 1.5GB UFS file to /dev/null and, once > that is finished, start mairix on my ~6GB mail directory (on ZFS > /home). After some time, I get the following 'systat -v' output: > > 4 users Load 9.30 8.97 8.33 Jul 14 09:49 > > Mem:KB REAL VIRTUAL VN PAGER SWAP PAGER > Tot Share Tot Share Free in out in out > Act 122308 4436 721892 7876 59824 count > All 418376 7020 1074594k 38920 pages > Proc: Interrupts > r p d s w Csw Trp Sys Int Sof Flt cow 4031 total > 4 76 133k 3 194 30 135 zfod ata0 irq14 > ozfod 30 bge0 irq16 > 99.8%Sys 0.2%Intr 0.0%User 0.0%Nice 0.0%Idle %ozfod atapci1 20 > | | | | | | | | | | | daefr uhci0 ehci > ================================================== prcfr uhci1 22 > dtbuf totfr 2000 cpu0: time > Namei Name-cache Dir-cache 100000 desvn react 2001 cpu1: time > Calls hits % hits % 918 numvn pdwak > 273 frevn pdpgs > intrn > Disks ad0 ad1 540404 wire > KB/t 0.00 0.00 297512 act > tps 0 0 1122808 inact > MB/s 0.00 0.00 57876 cache > %busy 0 0 1948 free > 218192 buf > > Apart from normal daemons, the only processes running are vmstat, > systat and mairix (via SSH sessions). Note that the system is running > at virtually 100%sys with extremely low free memory and extremely high > context switches but no obviously useful activity. At this stage, the > system is basically unusable (I can't even kill the mairix process). > > My understanding of the problem is that the VM system sees "available" > RAM as the sum of "cache" and "free" - which is reasonably high so > there is no pressure to free up "inact" RAM. OTOH, ZFS ARC only > counts "free" RAM - which is critically low so it throttles itself > but has no way to get the VM system to move RAM onto the "free" list. >
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