Date: Mon, 30 Jun 2014 19:14:16 +0200
From: Andres Freund <andres@2ndquadrant.com>
To: Heikki Linnakangas <hlinnakangas@vmware.com>
Cc: Soni M <diptatapa@gmail.com>, pgsql-performance@postgresql.org
Subject: Re: Postgres Replaying WAL slowly
Message-ID: <20140630171416.GK21422@awork2.anarazel.de>
References: 
 <CAAMgDXm5Y9QPELKvCGBrFvPcuR0ENVA1tEYRcazhDSxs6xnX5w@mail.gmail.com>
 <53AFCEE3.4080009@vmware.com>
 <CAAMgDXnKknBDk+Zb3BXau1cKV7y1A0vd9CJpX=vkSTXVGBrZwA@mail.gmail.com>
 <53B10C4C.8090701@vmware.com>
 <CAAMgDX=c8_6tutCDNiu38Z4wguKMGbhqznVNyMiOC5PZBpn1Fw@mail.gmail.com>
 <53B18CE0.4060501@vmware.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <53B18CE0.4060501@vmware.com>
Precedence: bulk
Sender: pgsql-performance-owner@postgresql.org

On 2014-06-30 19:14:24 +0300, Heikki Linnakangas wrote:
> On 06/30/2014 05:46 PM, Soni M wrote:
> >Here's what 'perf top' said on streaming replica :
> >
> >Samples: 26K of event 'cpu-clock', Event count (approx.): 19781
> >  95.97%  postgres                             [.] 0x00000000002210f3
> 
> Ok, so it's stuck doing something.. Can you get build with debug symbols
> installed, so that we could see the function name?

My guess it's a spinlock, probably xlogctl->info_lck via
RecoveryInProgress(). Unfortunately inline assembler doesn't always seem
to show up correctly in profiles...

What worked for me was to build with -fno-omit-frame-pointer - that
normally shows the callers, even if it can't generate a proper symbol
name.

Soni: Do you use Hot Standby? Are there connections active while you
have that problem? Any other processes with high cpu load?

Greetings,

Andres Freund

-- 
 Andres Freund	                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services


-- 
Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance