Message-ID: <0d84c025e38673cb575dcf4987d050fe7b1e1a1f.camel@j-davis.com>
Subject: Re: Improve WALRead() to suck data directly from WAL buffers when
 possible
From: Jeff Davis <pgsql@j-davis.com>
To: Andres Freund <andres@anarazel.de>
Cc: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Dilip Kumar
	 <dilipbalaut@gmail.com>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, 
	pgsql-hackers@lists.postgresql.org
Date: Tue, 03 Oct 2023 16:05:32 -0700
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On Sat, 2023-01-14 at 12:34 -0800, Andres Freund wrote:
> One benefit would be that it'd make it more realistic to use direct
> IO for WAL
> - for which I have seen significant performance benefits. But when we
> afterwards have to re-read it from disk to replicate, it's less
> clearly a win.

Does this patch still look like a good fit for your (or someone else's)
plans for direct IO here? If so, would committing this soon make it
easier to make progress on that, or should we wait until it's actually
needed?

If I recall, this patch does not provide a perforance benefit as-is
(correct me if things have changed) and I don't know if a reduction in
syscalls alone is enough to justify it. But if it paves the way for
direct IO for WAL, that does seem worth it.

Regards,
	Jeff Davis