Date: Tue, 07 Feb 2012 12:46:45 +0200 From: Andriy Gapon <avg@FreeBSD.org> To: "Eugene M. Zheganin" <emz@norma.perm.ru> Cc: freebsd-stable <freebsd-stable@FreeBSD.org> Subject: Re: zfs arc and amount of wired memory Message-ID: <4F310115.3070507@FreeBSD.org> In-Reply-To: <4F30E284.8080905@norma.perm.ru> References: <4F30E284.8080905@norma.perm.ru>
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on 07/02/2012 10:36 Eugene M. Zheganin said the following: > Hi. > > I have a server with 9.0/amd64 and 4 Gigs of RAM. > Today's questions are about the amount of memory in 'wired' state and the ARC size. > > If I use the script from http://wiki.freebsd.org/ZFSTuningGuide , it says: > > ===Cut=== > ARC Size: 12.50% 363.14 MiB > Target Size: (Adaptive) 12.50% 363.18 MiB > Min Size (Hard Limit): 12.50% 363.18 MiB > Max Size (High Water): 8:1 2.84 GiB > ===Cut=== > > At the same time I have 3500 megs in wired state: > > ===Cut=== > Mem: 237M Active, 36M Inact, 3502M Wired, 78M Cache, 432K Buf, 37M Free > ===Cut=== > > First question - what is the actual size of ARC, and how can it be determined ? > Solaris version of the script is more comprehensive (ran on Solaris): > > ===Cut=== > ARC Size: > Current Size: 6457 MB (arcsize) > Target Size (Adaptive): 6457 MB (c) > Min Size (Hard Limit): 2941 MB (zfs_arc_min) > Max Size (Hard Limit): 23534 MB (zfs_arc_max) > ===Cut=== Please try sysutils/zfs-stats; zfs-stats -a output should provide a good overview of the state and configuration of the system. > The arcstat script makes me think that the ARC size is about 380 megs indeed: > > ===Cut=== > Time read miss miss% dmis dm% pmis pm% mmis mm% size tsize > 14:33:35 170M 7466K 4 7466K 4 192 78 793K 3 380M 380M > ===Cut=== > > Second question: if the size is 363 Megs, why do I have 3500 Megs in wired > state? From my experience this is directly related to the zfs, but 380 megs its > like about ten times smaller than 3600 megs. At the same time I have like 700 > Megs in swap, so my guess - zfs isn't freeing memory for current needs that easily. > > Yeah, I can tune it down, but I just would like to know what is happening on an > untuned machine. -- Andriy Gapon
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