Date: Mon, 2 Apr 2018 05:11:59 +0000 (UTC) From: Gleb Smirnoff <glebius@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r331871 - head/sys/vm Message-ID: <201804020511.w325Bx89014264@repo.freebsd.org>
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Author: glebius Date: Mon Apr 2 05:11:59 2018 New Revision: 331871 URL: https://svnweb.freebsd.org/changeset/base/331871 Log: Handle a special case when a slab can fit only one allocation, and zone has a large alignment. With alignment taken into account uk_rsize will be greater than space in a slab. However, since we have only one item per slab, it is always naturally aligned. Code that will panic before this change with 4k page: z = uma_zcreate("test", 3984, NULL, NULL, NULL, NULL, 31, 0); uma_zalloc(z, M_WAITOK); A practical scenario to hit the panic is a machine with 56 CPUs and 2 NUMA domains, which yields in zone size of 3984. PR: 227116 MFC after: 2 weeks Modified: head/sys/vm/uma_core.c Modified: head/sys/vm/uma_core.c ============================================================================== --- head/sys/vm/uma_core.c Sun Apr 1 22:59:53 2018 (r331870) +++ head/sys/vm/uma_core.c Mon Apr 2 05:11:59 2018 (r331871) @@ -1290,7 +1290,15 @@ keg_small_init(uma_keg_t keg) else shsize = sizeof(struct uma_slab); - keg->uk_ipers = (slabsize - shsize) / rsize; + if (rsize <= slabsize - shsize) + keg->uk_ipers = (slabsize - shsize) / rsize; + else { + /* Handle special case when we have 1 item per slab, so + * alignment requirement can be relaxed. */ + KASSERT(keg->uk_size <= slabsize - shsize, + ("%s: size %u greater than slab", __func__, keg->uk_size)); + keg->uk_ipers = 1; + } KASSERT(keg->uk_ipers > 0 && keg->uk_ipers <= SLAB_SETSIZE, ("%s: keg->uk_ipers %u", __func__, keg->uk_ipers));
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