Date: Thu, 23 Apr 2015 12:49:51 -0600 From: Scott Long <scott4long@yahoo.com> To: Dmitry Chagin <dchagin@FreeBSD.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r281451 - head/sys/vm Message-ID: <4E109480-FD27-4C7F-8B5F-B1DB2232CD3D@yahoo.com> In-Reply-To: <5B48434B-EA97-45B3-BC4E-B039A868186B@yahoo.com> References: <201504120621.t3C6LxAV095209@svn.freebsd.org> <5B48434B-EA97-45B3-BC4E-B039A868186B@yahoo.com>
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> On Apr 23, 2015, at 6:19 AM, Scott Long <scott4long@yahoo.com> wrote: > >> >> On Apr 12, 2015, at 12:21 AM, Dmitry Chagin <dchagin@FreeBSD.org> wrote: >> >> Author: dchagin >> Date: Sun Apr 12 06:21:58 2015 >> New Revision: 281451 >> URL: https://svnweb.freebsd.org/changeset/base/281451 >> >> Log: >> Rework r281162. Indeed, the flexible array member is preferable here. >> >> Suggested by: Justin T. Gibbs >> >> MFC after: 3 days >> >> Modified: >> head/sys/vm/uma_core.c >> head/sys/vm/uma_int.h > > There’s still something wrong with this. I have a machine with 28 cores (56 with hyperthreading) and 256GB of RAM, and ever since you committed r281162, it panics early in boot with a failed assertion. It looks like the first few members of a uma_slab_t are getting overwritten accidentally, and somehow the padding of the extra member in the uma_zone_t was previously protecting it. I don’t know the exact cause yet, but I must ask that you revert to r281161 in HEAD and stable/10 until the problem is resolved. > I think the problem is that the masterzone_k and masterzone_z objects that are statically allocated in uma_core.c no longer have space for the uz_cpu field, but uma_zalloc_arg() always assumes that it’s there. Early in boot when the ‘kegs' and ‘zones’ zones are being initialized, there’s only 1 CPU so pre-allocating 1 uz_cpu element in the uma_zone is enough. I can’t see any way around this without significantly changing how uma_zalloc_arg() treats per-cpu caches. I think it’s best to revert this change. Scott
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