Date: Tue, 20 Mar 2012 18:37:57 +0300 From: Sergey Kandaurov <pluknet@gmail.com> To: Mark Saad <nonesuch@longcount.org> Cc: freebsd-hackers@freebsd.org Subject: Re: Approaching the limit on PV entries Message-ID: <CAE-mSOK-JswcJXRPMfMxVZpc0H5gZ5-iv5H4-zDDPxfau=E=vA@mail.gmail.com> In-Reply-To: <CAMXt9NapczKEmBU3Wwwh99jb6Vv9bhejxgpmVqStGBwvP7BmAA@mail.gmail.com> References: <CAMXt9NapczKEmBU3Wwwh99jb6Vv9bhejxgpmVqStGBwvP7BmAA@mail.gmail.com>
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On 22 November 2011 19:29, Mark Saad <nonesuch@longcount.org> wrote: > Hello All [found this mail in my drafts, not sure if my answer is still useful] > =A0I want to get to the bottom of a warning in dmesg. On 7.2-RELEASE and > 7.3-RELEASE I have seen the following warning in dmesg. > > Approaching the limit on PV entries, consider increasing either the > vm.pmap.shpgperproc or the vm.pmap.pv_entry_max sysctl. > > So looking around I see a few posts here and there about how to tune > the sysctls to address the warning however I am not 100% sure what > each value does. > It appears changing vm.pmap.shpgperproc affects the value of > vm.pmap.pv_entry_max . Can someone explain the relationship of the two > sysctls. Also This is how they are calculated. pv_entry_max =3D shpgperproc * maxproc + cnt.v_page_count; and, respectively, shpgperproc =3D (pv_entry_max - cnt.v_page_count) / maxproc; So, changing one sysctl will change another and vice versa. > what pitfalls of changing them are. Not known to me (on amd64 platform). I have had vm.pmap.shpgperproc=3D15000 on 8.1 amd64 with 4G RAM to make some badly written commercial software to work until it was decommissioned to the scrap. > Also why would setting > kern.ipc.shm_use_phys=3D1 =A0effect the pv entries. Is this supposed to > lower the pv entries ? Changing this sysctl with restarting a quite busy PgSQL server helped me to reduce pv entries from 14M to tens of thousands (though that could just coincide with decrease in workload). --=20 wbr, pluknet
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