Date: Mon, 05 May 2008 17:39:23 -0500 From: Guy Helmer <ghelmer@palisadesys.com> To: freebsd-stable@freebsd.org Subject: Puzzling VM behavior in 6.3 Message-ID: <481F8C9B.1080508@palisadesys.com>
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I'm trying to track down a performance regression in a memory-hungry
application that seems to be related to switching from FreeBSD 6 as of
2007-01-04 (6.2-ish) to a checkout as of 2007-10-04 (6.3-ish). With
these two systems running identical software under load side-by-side on
identical hardware, we've observed that the disk is busier on the 6.3
system under the same load, but there shouldn't be much file activity
other than logging and the swap usage stays at 0.
In trying to track this down, we've found the most significant
differences are in statistics from parts of the VM system. A partial
snapshot of "systat -vm" shows this:
6-STABLE 2007-10-04 sample
Mem:KB REAL VIRTUAL VN PAGER SWAP
PAGER
Tot Share Tot Share Free in out in
out
Act 2174196 16428 2489520 29168 166416 count
All 2340816 28304 6887896 45636 pages
6-STABLE 2007-01-04 sample
Mem:KB REAL VIRTUAL VN PAGER SWAP PAGER
Tot Share Tot Share Free in out in out
Act 2092808 15184 2439012 25424 202272 count
All 3949748 20856157408972 34392 pages
We've also noticed large differences in some sysctl vm stats:
6-STABLE 2007-01-04 6-STABLE 2007-10-04
vm.stats.vm.v_forkpages: 660926510 1607169036
vm.stats.vm.v_pdpages: 608941 1793198
Does this information give anyone a clue as to where I should look next?
Thanks for any help,
Guy
--
Guy Helmer, Ph.D.
Chief System Architect
Palisade Systems, Inc.
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