Re: High SYS CPU - need advise

On Tue, Nov 20, 2012 at 8:03 AM, Merlin Moncure <mmoncure(at)gmail(dot)com> wrote:
> On Tue, Nov 20, 2012 at 9:02 AM, Shaun Thomas <sthomas(at)optionshouse(dot)com> wrote:
>> On 11/16/2012 02:31 PM, Merlin Moncure wrote:
>>
>>> no single thing really stands out -- contention is all over the place.
>>> lwlock, pinbuffer, dynahash (especially). I am again suspicious of
>>> bad scheduler interaction. any chance we can fire up pgbouncer?
>>
>>
>> Just want to throw it out there, but we've been having really bad luck with
>> the scheduler recently. But only when we use 8GB (on our 72GB system) for
>> shared_buffers. Cut that down to 4GB, and everything is fine and dandy.
>>
>> I think the kernel devs have added in some overzealous scheduler code on us.
>
> Shared buffer manipulation changing contention is suggesting you're
> running into free list lock issues.

I wouldn't expect so. Increasing shared_buffers should either fix
free list lock contention, or leave it unchanged, not make it worse.
Sounds more like that NUMA/interleave/zone reclaim stuff I could never
wrap my head around.

Cheers,

Jeff