Date: Mon, 29 Mar 2010 12:27:23 -0400 From: Ben Kelly <ben@wanderview.com> To: Barry Pederson <bp@barryp.org> Cc: jhell <jhell@DataIX.net>, FreeBSD Stable <freebsd-stable@freebsd.org> Subject: Re: ZFS Tuning - arc_summary.pl Message-ID: <6823460E-4878-4936-A827-75BBA97F2304@wanderview.com> In-Reply-To: <4BB0BC7C.3000801@barryp.org> References: <cf9b1ee01002150049o43fced71ucb5776a0a1eaf4cf@mail.gmail.com> <20100215090756.GA54764@icarus.home.lan> <20100215105000.101326yj01j0f64g@webmail.leidinger.net> <20100215122744.GA57382@icarus.home.lan> <20100215161105.14071eiflhc9le68@webmail.leidinger.net> <4B79BA9C.3020402@quip.cz> <alpine.BSF.2.00.1002152024040.74553@pragry.qngnvk.ybpny> <4B7AD0A3.9080701@barryp.org> <alpine.BSF.2.00.1002170321200.14189@pragry.qngnvk.ybpny> <4BB0BC7C.3000801@barryp.org>
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On Mar 29, 2010, at 10:43 AM, Barry Pederson wrote: > I've been using the arc_summary.pl script from here: >=20 > = http://jhell.googlecode.com/svn/base/head/scripts/zfs/arc_summary/arc_summ= ary.pl >=20 > and noticed some odd numbers, with the ARC Current Size being larger = than the Max Size, and the breakdown adding up to less than the current = size as shown below I believe the current size can be larger than the max if your working = data set is large enough. The ARC can't evict data that is still being = referenced. When I last looked (over a year ago) there was no mechanism = to provide back pressure from the ARC to the VM layer to request that = more nodes be released to help deal with this situation. I don't know if that really helps at all, but I just thought I would add = the data point from my previous debugging sessions with zfs. - Ben=
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