Re: Read-ahead and parallelism in redo recovery

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Decibel! <decibel(at)decibel(dot)org>
Cc: Florian Weimer <fweimer(at)bfk(dot)de>, "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com>, "PostgreSQL-development Hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Read-ahead and parallelism in redo recovery
Date: 2008-02-29 20:47:15
Message-ID: 12563.1204318035@sss.pgh.pa.us
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Decibel! <decibel(at)decibel(dot)org> writes:
> Perhaps a good short-term measure would be to have recovery allocate
> a 16M buffer and read in entire xlog files at once.

If that isn't entirely useless, you need a better kernel. The system
should *certainly* be bright enough to do read-ahead for our reads of
the source xlog file. The fetches that are likely to be problematic are
the ones for pages in the data area, which will be a lot less regular
for typical workloads.

regards, tom lane

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