Approaching the limit on PV entries

[Stephen Clark]

Alfred Perlstein wrote:
> * Ivan Voras <ivoras at freebsd.org> [080311 08:46] wrote:
>   
>> During heavy postgresql load (pgbench), /var/log/messages registers
>> (multiple times) the following message:
>>
>> "Approaching the limit on PV entries, consider increasing either the
>> vm.pmap.shpgperproc or the vm.pmap.pv_entry_max sysctl"
>>
>> I'm increasing both, but no matter what I increase them to, after a
>> short time they again get increased by the system (???).
>>
>> The values are currently:
>>
>> vm.pmap.shpgperproc: 1134
>> vm.pmap.pv_entry_max: 8000000
>>
>> But the last sysctl setting, verified by retrieving it from my shell
>> command line history, is that I set vm.pmap.shpgperproc to 800.
>>
>> Is this normal, and what are the common settings for these values? The
>> machine is 2x4-core, currently 4 GB RAM (which will increase to at least
>> 6 GB), amd64, running postgresql, php and apache.
>>
>>     
>
> try setting:
>
> sysctl kern.ipc.shm_use_phys=1
>
>
>
>   
Could you please explain what that does and why?

Also could someone point me to where all these sysctls are documented 
other than in the source code - which lots
of time has no explanation. It would really help the average sys admin/ 
user if these were documented.

Thanks,
Steve

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