| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com> |
| Cc: | Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Proposal for 9.1: WAL streaming from WAL buffers |
| Date: | 2010-06-14 15:02:52 |
| Message-ID: | 13213.1276527772@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Fujii Masao <masao(dot)fujii(at)gmail(dot)com> writes:
> On Fri, Jun 11, 2010 at 11:47 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Well, we're already not waiting for fsync, which is the slowest part.
> No, currently walsender waits for fsync.
No, you're mistaken.
> Walsender tries to send WAL up to xlogctl->LogwrtResult.Write. OTOH,
> xlogctl->LogwrtResult.Write is updated after XLogWrite() performs fsync.
Wrong. LogwrtResult.Write tracks how far we've written out data,
but it is only (known to be) fsync'd as far as LogwrtResult.Flush.
> But that change would cause the problem that Robert pointed out.
> http://archives.postgresql.org/pgsql-hackers/2010-06/msg00670.php
Yes. Possibly walsender should only be allowed to send as far as
LogwrtResult.Flush.
regards, tom lane
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