| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
| Cc: | Simon Riggs <simon(at)2ndQuadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: corrupt pages detected by enabling checksums |
| Date: | 2013-04-05 00:39:16 |
| Message-ID: | 1365122356.14231.72.camel@jdavis |
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| Lists: | pgsql-hackers |
On Thu, 2013-04-04 at 22:39 +0200, Andres Freund wrote:
> I don't think its really slower. Earlier the code took WalInsertLock
> everytime, even if we ended up not logging anything. Thats far more
> epensive than a single spinlock. And the copy should also only be taken
> in the case we need to log. So I think we end up ahead of the current
> state.
Good point.
> > The code looks good to me except that we should be consistent about the
> > page hole -- XLogCheckBuffer is calculating it, but then we copy the
> > entire page. I don't think anything can change the size of the page hole
> > while we have a shared lock on the buffer, so it seems OK to skip the
> > page hole during the copy.
>
> I don't think it can change either, but I doubt that there's a
> performance advantage by not copying the hole. I'd guess the simpler
> code ends up faster.
I was thinking more about the WAL size, but I don't have a strong
opinion.
Regards,
Jeff Davis
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