From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Joe Conway <mail(at)joeconway(dot)com> |
Cc: | Andres Freund <andres(at)2ndquadrant(dot)com>, "Hackers (PostgreSQL)" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Excessive WAL generation and related performance issue |
Date: | 2014-04-15 21:13:10 |
Message-ID: | 3933.1397596390@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Joe Conway <mail(at)joeconway(dot)com> writes:
> In other words, based on my inserted logic, it appears that there are
> 5 and 6 backup blocks on a fairly regular basis.
> However in xlog.h it says:
> 8<--------------------------
> * If we backed up any disk blocks with the XLOG record, we use flag
> * bits in xl_info to signal it. We support backup of up to 4 disk
> * blocks per XLOG record.
> 8<--------------------------
> So is my logic to record number of backup blocks wrong, or is the
> comment wrong, or am I otherwise misunderstanding something?
The comment is correct, so you did something wrong. From memory,
there's a goto-label retry loop in that function; maybe you need
to zero your counters after the retry label?
regards, tom lane
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