Date: Tue, 3 Jan 2012 13:39:28 -0800 From: David Wolfskill <david@catwhisker.org> To: performance@freebsd.org Subject: vm.exec_map_entries vs. hw.ncpu vs. ...? Message-ID: <20120103213928.GP1733@albert.catwhisker.org>
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--4SRTEifjNkXp0Rce Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable A colleague at work has been researching the nature of some issues we're seeing in a FreeBSD/amd64 release/8.2.0 environment in which amd (which is providing services to a jail, where the "useful work" actually gets done) is apparently failing (on occasion) to perform the work it is supposed to do because vm.exec_map_entries is set too low. vm.exec_map_entries default value is 16 -- see src/sys/vm/vm_init.c:91-94: static int exec_map_entries =3D 16; TUNABLE_INT("vm.exec_map_entries", &exec_map_entries); SYSCTL_INT(_vm, OID_AUTO, exec_map_entries, CTLFLAG_RD, &exec_map_entries, = 0, "Maximum number of simultaneous execs"); We had not previously modified the setting. The machines in question are dual-package, 6-core machines with Intel's SMT (Simultaneous Multi-Threading) enabled, so hw.ncpu is 24. Is it reasonable for exec_map_entries to be thus initialized, independently of number of logical cores, kern.maxusers, amount of memory, or anything else? Are there guidelines or suggestions for setting it? Apparently each entry consumes a bit over 200KB, so making it arbitrarily large is probably not a good idea. :-} I don't see it mentioned in tuning(7). Thanks for any inisight. Peace, david --=20 David H. Wolfskill david@catwhisker.org Depriving a girl or boy of an opportunity for education is evil. See http://www.catwhisker.org/~david/publickey.gpg for my public key. --4SRTEifjNkXp0Rce Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (FreeBSD) iEYEARECAAYFAk8DdY8ACgkQmprOCmdXAD0uRgCfZKODGaZcA/ZsB73aqYHRTveq XbEAoIMqTRc8vMGP8dOMg8yab2m7BG5w =7beb -----END PGP SIGNATURE----- --4SRTEifjNkXp0Rce--
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