Date: Wed, 21 Mar 2012 16:20:17 -0400 From: Mark Saad <nonesuch@longcount.org> To: freebsd-hackers@freebsd.org Subject: Re: Approaching the limit on PV entries Message-ID: <CAMXt9NZbn8OAvRQVvYSi8c2N2ajfASjDnXDwyXqKsFr9B%2BJOtA@mail.gmail.com> In-Reply-To: <CAE-mSOJw1wo9SqtfDfH9Qn30cUKyuiB1aTTwqdQU7-5iDrFdPg@mail.gmail.com> References: <CAMXt9NapczKEmBU3Wwwh99jb6Vv9bhejxgpmVqStGBwvP7BmAA@mail.gmail.com> <CAE-mSOK-JswcJXRPMfMxVZpc0H5gZ5-iv5H4-zDDPxfau=E=vA@mail.gmail.com> <201203211119.43022.jhb@freebsd.org> <CAE-mSOJw1wo9SqtfDfH9Qn30cUKyuiB1aTTwqdQU7-5iDrFdPg@mail.gmail.com>
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On Wed, Mar 21, 2012 at 12:39 PM, Sergey Kandaurov <pluknet@gmail.com> wrot= e: > On 21 March 2012 19:19, John Baldwin <jhb@freebsd.org> wrote: >> On Tuesday, March 20, 2012 11:37:57 am Sergey Kandaurov wrote: >>> 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] >>> >>> > =C2=A0I want to get to the bottom of a warning in dmesg. On 7.2-RELEA= SE 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 tw= o >>> > 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. >> >> FYI, Alan just removed this warning and the associated sysctls from HEAD >> yesterday because they were made obsolete several years ago. =C2=A0I thi= nk they are >> obsolete even on 7. =C2=A0Certainly on 8. > > Yep, and since switching to direct map (somewhere around 7.x on amd64?) > made PV entry limit factually obsolete, this is really cool. > > -- > wbr, > pluknet Interesting so this warning is relevant in 7.x ? --=20 mark saad | nonesuch@longcount.org
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