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From: Matthew Wilcox <willy@infradead.org>
To: Steve French <smfrench@gmail.com>
Cc: linux-nfs <linux-nfs@vger.kernel.org>,
	CIFS <linux-cifs@vger.kernel.org>,
	v9fs-developer@lists.sourceforge.net,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: Removing readpages aop
Date: Thu, 13 May 2021 14:34:35 +0100	[thread overview]
Message-ID: <YJ0q6/Oe5yJ+H+Tn@casper.infradead.org> (raw)
In-Reply-To: <CAH2r5msOQsdeknBdTsfMXYzrb5=NuKEBPc4WD1CkYp10t19Guw@mail.gmail.com>

On Wed, May 12, 2021 at 02:28:41PM -0500, Steve French wrote:
> I don't have any objections as long as:
> - we see at least mild performance benefit (or at least we are
> confident that no performance loss)

Nobody's complained of a performance loss in the other ~30 filesystems
which have already been converted (some almost a year ago).  And CIFS
has one of the more convoluted readpages implementation, so I'd expect
a higher likelihood of a performance gain from CIFS.

> - it passes regression tests (the usual xfstest bucket)
> - it doesn't complicate the code too much (sounds like it actually
> might simplify it, but needs a little more work)
> - make sure that the usual tuning parms still work (e.g. "rsize" and
> "rasize" mount options) or we can figure out a sane way to autotune
> readhead so those wouldn't be needed for any workload

One of the enhancements added as part of the recent netfs merge
was readahead_expand().  Take a look at it and see if it works for you.

> But currently since we get the most benefit from multichannel (as that
> allows even better parallelization of i/o) ... I have been focused on
> various multichannel issues (low credit situations, reconnect, fall
> back to different channels when weird errors, adjusting channels
> dynamically when server adds or removes adapters on the fly) for the
> short term

Understood.  Only so many hours in the day.

I think
https://lore.kernel.org/linux-fsdevel/1794123.1605713481@warthog.procyon.org.uk/
is the most recent version, but as Dave notes, it needs attention from
somebody who knows the CIFS code better.

  reply	other threads:[~2021-05-13 13:38 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-12 15:12 Matthew Wilcox
2021-05-12 19:28 ` Steve French
2021-05-13 13:34   ` Matthew Wilcox [this message]
2021-05-12 21:24 ` [V9fs-developer] " Dominique Martinet

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