Re: Cpu usage 100% on slave. s_lock problem.

On Tue, Sep 17, 2013 at 8:24 AM, Andres Freund <andres@2ndquadrant.com> wrote:
> On 2013-09-17 08:18:54 -0500, Merlin Moncure wrote:
>> Do you think it's worth submitting the lock avoidance patch for formal review?
>
> You mean the bufmgr.c thing? Generally I think that that code needs a
> good of scalability work - there's a whole thread about it
> somewhere. But TBH the theories you've voiced about the issues you've
> seen haven't convinced me so far.

er, no (but I share your skepticism -- my challenge right now is to
demonstrate measurable benefit which so far I've been unable to do).
I was talking about the patch on  *this* thread which bypasses the
s_lock in RecoveryInProgress()  :-).

> Quick question: Do you happen to have pg_locks output from back then
> around? We've recently found servers going into somewhat similar
> slowdowns because they exhausted the fastpath locks which made lwlocks
> far more expensive and made s_lock go up very high in the profle.

I do. Unfortunately I don't have profile info.   Not sure how useful
it is -- I'll send it off-list.

merlin