Date: Mon, 2 Apr 2012 17:19:21 -0400 From: Mark Saad <nonesuch@longcount.org> To: freebsd-hackers@freebsd.org Subject: Re: Approaching the limit on PV entries Message-ID: <CAMXt9Na6WksLSc1-%2BhXSQhKzCTSORbMT0=a8eA3buDCtXzectg@mail.gmail.com> In-Reply-To: <201204021123.53055.jhb@freebsd.org> References: <CAMXt9NapczKEmBU3Wwwh99jb6Vv9bhejxgpmVqStGBwvP7BmAA@mail.gmail.com> <201203220803.57000.jhb@freebsd.org> <CAMXt9NbY9Opz6r2JpLrOGEZ3nU3amc5-5xLcKA0CyFq19mMZBg@mail.gmail.com> <201204021123.53055.jhb@freebsd.org>
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On Mon, Apr 2, 2012 at 11:23 AM, John Baldwin <jhb@freebsd.org> wrote: > On Thursday, March 22, 2012 1:48:29 pm Mark Saad wrote: >> On Thu, Mar 22, 2012 at 8:03 AM, John Baldwin <jhb@freebsd.org> wrote: >> > On Wednesday, March 21, 2012 4:20:17 pm Mark Saad wrote: >> >> On Wed, Mar 21, 2012 at 12:39 PM, Sergey Kandaurov <pluknet@gmail.com= > wrote: >> >> > 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> wro= te: >> >> >>> > Hello All >> >> >>> >> >> >>> [found this mail in my drafts, not sure if my answer is still use= ful] >> >> >>> >> >> >>> > =C2=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 w= hat >> >> >>> > 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. >> >> >> >> >> >> FYI, Alan just removed this warning and the associated sysctls fro= m HEAD >> >> >> yesterday because they were made obsolete several years ago. =C2= =A0I think they are >> >> >> obsolete even on 7. =C2=A0Certainly on 8. >> >> > >> >> > Yep, and since switching to direct map (somewhere around 7.x on amd= 64?) >> >> > made PV entry limit factually obsolete, this is really cool. >> >> > >> >> > -- >> >> > wbr, >> >> > pluknet >> >> >> >> Interesting so this warning is relevant in 7.x ? >> > >> > No, looks like it was obsolete starting with 7.0. >> > >> > -- >> > John Baldwin >> >> Any chance it could be mfc'ed to 7-STABLE ? > > I just merged it to stable/7. > > -- > John Baldwin Thanks again john . --=20 mark saad | nonesuch@longcount.org
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