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Re: [PATCH 0/2] block: add logging facility for long standing IO request
Denis V. Lunev
Re: [PATCH 0/2] block: add logging facility for long standing IO requests
Fri, 31 Jul 2020 13:31:51 +0300
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On 7/31/20 1:25 PM, Stefan Hajnoczi wrote:
> On Fri, Jul 10, 2020 at 08:27:09PM +0300, Denis V. Lunev wrote:
>> There are severe delays with IO requests processing if QEMU is running in
>> virtual machine or over software defined storage. Such delays potentially
>> results in unpredictable guest behavior. For example, guests over IDE or
>> SATA drive could remount filesystem read-only if write is performed
>> longer than 10 seconds.
>> Such reports are very complex to process. Some good starting point for this
>> seems quite reasonable. This patch provides one. It adds logging of such
>> potentially dangerous long IO operations.
>> Signed-off-by: Denis V. Lunev <email@example.com>
>> CC: Vladimir Sementsov-Ogievskiy <firstname.lastname@example.org>
>> CC: Kevin Wolf <email@example.com>
>> CC: Max Reitz <firstname.lastname@example.org>
> If I understand correctly this only reports completed I/Os, so if the
> host hasn't given up on an I/O request yet then QEMU will not report it
> is taking a long time. In the meantime the guest could start printing
> timeout errors.
> I think this patch series is good as it is. In the future maybe a QMP
> command that lists in-flight I/O requests would be nice. That helps
> when troubleshooting I/Os that are hung.
We could dump requests at block level, we do have proper lists,
but the would be a little bit different.
Anyway, I __DO__ like this idea, I have missed this somehow :)
Thank you for the suggestion,