From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
To: Max Reitz <mreitz@redhat.com>,
"qemu-block@nongnu.org" <qemu-block@nongnu.org>
Cc: "kwolf@redhat.com" <kwolf@redhat.com>,
Denis Lunev <den@virtuozzo.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"armbru@redhat.com" <armbru@redhat.com>,
"stefanha@redhat.com" <stefanha@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v3 0/4] qcow2: async handling of fragmented io
Date: Fri, 16 Aug 2019 16:42:37 +0000 [thread overview]
Message-ID: <8d3ca847-a3c6-6e22-344d-d63b5dc5667f@virtuozzo.com> (raw)
In-Reply-To: <8c259ef0-ccce-5fd0-6c88-4f0a2109715c@virtuozzo.com>
15.08.2019 18:39, Vladimir Sementsov-Ogievskiy wrote:
> 15.08.2019 17:09, Max Reitz wrote:
>> On 15.08.19 14:10, Vladimir Sementsov-Ogievskiy wrote:
>>> Hi all!
>>>
>>> Here is an asynchronous scheme for handling fragmented qcow2
>>> reads and writes. Both qcow2 read and write functions loops through
>>> sequential portions of data. The series aim it to parallelize these
>>> loops iterations.
>>> It improves performance for fragmented qcow2 images, I've tested it
>>> as described below.
>>
>> Looks good to me, but I can’t take it yet because I need to wait for
>> Stefan’s branch to be merged, of course.
>>
>> Speaking of which, why didn’t you add any tests for the *_part()
>> methods? I find it a bit unsettling that nothing would have caught the
>> bug you had in v2 in patch 3.
>>
>
> Hmm, any test with write to fragmented area should have caught it.. Ok,
> I'll think of something.
>
>
And now I see that it's not trivial to make such a test:
1. qcow2 write is broken when we give nonzero qiov_offset to it, but only
qcow2_write calls bdrv_co_pwritev_part, so we need to have a test where qcow2
is a file child for qcow2
2. Then, the bug leads to the beginning of the qiov will be written to all parts.
But our testing tool qemu-io has only "write -P" command with buffer filled with
the same one byte, so we can't catch it
--
Best regards,
Vladimir
prev parent reply other threads:[~2019-08-16 16:43 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-15 12:10 [Qemu-devel] [PATCH v3 0/4] qcow2: async handling of fragmented io Vladimir Sementsov-Ogievskiy
2019-08-15 12:10 ` [Qemu-devel] [PATCH v3 1/4] block: introduce aio task pool Vladimir Sementsov-Ogievskiy
2019-08-15 13:41 ` Max Reitz
2019-08-15 12:10 ` [Qemu-devel] [PATCH v3 2/4] block/qcow2: refactor qcow2_co_preadv_part Vladimir Sementsov-Ogievskiy
2019-08-15 13:56 ` Max Reitz
2019-08-15 12:10 ` [Qemu-devel] [PATCH v3 3/4] block/qcow2: refactor qcow2_co_pwritev_part Vladimir Sementsov-Ogievskiy
2019-08-15 14:02 ` Max Reitz
2019-08-15 12:10 ` [Qemu-devel] [PATCH v3 4/4] block/qcow2: introduce parallel subrequest handling in read and write Vladimir Sementsov-Ogievskiy
2019-08-15 14:07 ` Max Reitz
2019-08-15 13:21 ` [Qemu-devel] [PATCH v3 0/4] qcow2: async handling of fragmented io Max Reitz
2019-08-15 15:35 ` Vladimir Sementsov-Ogievskiy
2019-08-15 14:09 ` Max Reitz
2019-08-15 15:39 ` Vladimir Sementsov-Ogievskiy
2019-08-16 16:42 ` Vladimir Sementsov-Ogievskiy [this message]
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