Approaching the limit on PV entries
nonesuch at longcount.org
Wed Mar 21 20:20:19 UTC 2012
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.
Interesting so this warning is relevant in 7.x ?
mark saad | nonesuch at longcount.org
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