Re: WAL and commit_delay

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, vadim4o(at)email(dot)com
Subject: Re: WAL and commit_delay
Date: 2001-02-17 19:05:17
Message-ID: 200102171905.OAA28285@candle.pha.pa.us
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> Actually ... take a close look at the code. The delay is done in
> xact.c between XLogInsert(commitrecord) and XLogFlush(). As near
> as I can tell, both the write() and the fsync() will happen in
> XLogFlush(). This means the delay is just plain broken: placed
> there, it cannot do anything except waste time.

I see. :-(

> Another thing I am wondering about is why we're not using fdatasync(),
> where available, instead of fsync(). The whole point of preallocating
> the WAL files is to make fdatasync safe, no?

I don't have fdatasync() here. How does it compare to fsync().

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