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From:   Chris Chilvers <chilversc@gmail.com>
Date:   Tue, 1 Mar 2022 15:34:56 +0000
Message-ID: <CAAmbk-fqYXQupHEyPk_iONzaNXRuH6Dz24gZw9Bvswx2X8EWgg@mail.gmail.com>
Subject: Re: [BUG] FS-Cache write but no read when using sync
To:     linux-nfs@vger.kernel.org
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You can disregard this message. I didn't realise there was a separate
mailing list for cachefs. I've re-posted the message to the correct
mailing list.

-- Chris

On Mon, 28 Feb 2022 at 19:24, Chris Chilvers <chilversc@gmail.com> wrote:
>
> While trying the new FS-Cache implementation using the 5.17-rc5 kernel on
> Ubuntu 21.10 I ran into an issue where it appears that FS-Cache was not being
> used when the sync mount option is enabled.
>
> While monitoring /proc/fs/fscache/stats it was observed there were high writes
> to the cache volume, but no reads:
>
>     IO     : rd=0 wr=344713665
>
> Further tracing of /sys/kernel/debug/tracing/events/fscache/fscache_access shows
> a large number of io_write operations, but no io_read operations.
>
> The volume did fill up and perform culling as expected.
>
> When the mount option was changed from sync to async the cache performed as
> expected and a mixture of io_write and io_read was observed.
>
> -- Chris