Date: Mon, 18 May 2009 18:26:51 -0700 From: Kip Macy <kmacy@freebsd.org> To: Adam McDougall <mcdouga9@egr.msu.edu> Cc: current@freebsd.org, Larry Rosenman <ler@lerctr.org> Subject: Re: Fatal trap 12: page fault panic with recent kernel with ZFS Message-ID: <3c1674c90905181826p787a346cie90429324444a9c4@mail.gmail.com> In-Reply-To: <20090519012202.GR82547@egr.msu.edu> References: <20090518145614.GF82547@egr.msu.edu> <alpine.BSF.2.00.0905181031240.35767@thebighonker.lerctr.org> <alpine.BSF.2.00.0905181830490.1756@borg> <3c1674c90905181659g1d20f0f1w3f623966ae4440ec@mail.gmail.com> <alpine.BSF.2.00.0905181906001.2008@borg> <20090519012202.GR82547@egr.msu.edu>
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On Mon, May 18, 2009 at 6:22 PM, Adam McDougall <mcdouga9@egr.msu.edu> wrot= e: > On Mon, May 18, 2009 at 07:06:57PM -0500, Larry Rosenman wrote: > > =A0On Mon, 18 May 2009, Kip Macy wrote: > > =A0> The ARC cache allocates wired memory. The ARC will grow until there = is > =A0> vm pressure. > =A0My crash this AM was with 4G real, and the ARC seemed to grow and grow= , then > =A0we started paging, and then crashed. > > =A0Even with the VM pressure it seemed to grow out of control. > > =A0Ideas? > > > Before that but since 191902 I was having the opposite problem, > my ARC and thus Wired would grow up to approx arc_max until my > Inactive memory put pressure on ARC making it shrink back down > to ~450M where some aspects of performance degraded. =A0A partial > workaround was to add a arc_min which isn't entirely successful > and I found I could restore ZFS performance by temporarily squeezing > down Inactive memory by allocating a bunch of it myself; after > freeing that, ARC had no pressure and could grow towards arc_max > again until Inactive eventually rose. =A0Reported to Kip last night > and some cvs commit lists. =A0I never did run into Swap. > That is a separate issue. I'm going to try adding a vm_lowmem event handler to drive reclamation instead of the current paging target. That shouldn't cause inactive pages to shrink the ARC. Most people consider out of the box stability more import than getting the maximum ARC. However, for people like you who want the safety catches removed I should make it possible to disable back-pressure. -Kip
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