Re: [CFT] ZFS v15 patch (version 3)
- From: Martin Matuska <mm@xxxxxxxxxxx>
- Date: Wed, 14 Jul 2010 09:16:09 +0200
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@xxxxxxxxxxx> wrote:_______________________________________________
On 8. 7. 2010 22:04, Peter Jeremy wrote / napísal(a):I have done some testing with 8-STABLE with head-12636.patch and have
Without patching arc_memory_throttle(), a system behaves especiallyRegarding ARC, you might want to try the revision 209227 from head that
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;'
is scheduled for MFC on 18.7.2010:
http://people.freebsd.org/~mm/patches/zfs/head-12636.patch
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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