Approaching the limit on PV entries

[John Baldwin]

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