Date: Mon, 23 Oct 2006 01:52:59 -0400 From: Jim Keller <jim@centerfuse.net> To: freebsd-questions@freebsd.org Subject: general VM / KMEM tunables question Message-ID: <453C58BB.6030108@centerfuse.net>
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Trying to tune a new system (FreeBSD 6.1) for the best performance (moderately busy webserver, but nothing over the top). However, I'm having a lot of trouble finding documentation on VM sysctl tunables. I have run into the (somewhat common) issue before of running out of PV_Entries due to Apache getting busy, so my current webserver kernels all have the following in them: options KVA_PAGES=512 options PMAP_SHPGPERPROC=401 However, these values were only chosen because they seemed to fix my problem, not because I'm entirely sure they're the best possible values. How does one go about determining how many KVA_PAGES and PMAP_SHPGPERPROC to set? Also, are there sysctl OIDs for these options? Poking around google, I've seen mention of vm.pmap.pv_entry_max and vm.pmap.shgperproc, but those OIDs do not exist on my system as far as I can tell. I also have the following in my sysctl.conf, but again I'm not sure how I initially came up with these figures (though they do work), and I wanted to get a better handle on my system tuning: vm.v_free_min=8192 vm.v_free_target=16384 vm.v_free_reserved=8192 vm.v_free_severe=16384 Basically just trying to get some clues as to how to figure out (based on system config) what these values should reasonably be set to. Thanks. -Jim Keller
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