Approaching the limit on PV entries

[John Baldwin]

On Thursday, March 22, 2012 1:48:29 pm Mark Saad wrote:
> On Thu, Mar 22, 2012 at 8:03 AM, John Baldwin <jhb at 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 at gmail.com> wrote:
> >> > On 21 March 2012 19:19, John Baldwin <jhb at freebsd.org> wrote:
> >> >> On Tuesday, March 20, 2012 11:37:57 am Sergey Kandaurov wrote:
> >> >>> On 22 November 2011 19:29, Mark Saad <nonesuch at longcount.org> wrote:
> >> >>> > Hello All
> >> >>>
> >> >>> [found this mail in my drafts, not sure if my answer is still useful]
> >> >>>
> >> >>> >  I 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 = shpgperproc * maxproc + cnt.v_page_count;
> >> >>>
> >> >>> and, respectively,
> >> >>>
> >> >>> shpgperproc = (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=15000 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.  I think they are
> >> >> obsolete even on 7.  Certainly 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 ?
> >
> > 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