From: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
To: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
Max Reitz <mreitz@redhat.com>,
qemu-block@nongnu.org
Cc: qemu-devel@nongnu.org, kwolf@redhat.com, fam@euphon.net,
stefanha@redhat.com, armbru@redhat.com, jsnow@redhat.com,
libvir-list@redhat.com, eblake@redhat.com, den@openvz.org
Subject: Re: [PATCH v11 09/13] copy-on-read: skip non-guest reads if no copy needed
Date: Thu, 22 Oct 2020 10:50:39 +0300 [thread overview]
Message-ID: <4ae47559-af39-1dcc-5e22-f7259b55dfee@virtuozzo.com> (raw)
In-Reply-To: <519fd52f-cb9e-0ab1-6d50-a9b3004d86fe@virtuozzo.com>
On 21.10.2020 23:43, Andrey Shinkevich wrote:
> On 14.10.2020 18:22, Vladimir Sementsov-Ogievskiy wrote:
>> 14.10.2020 15:51, Max Reitz wrote:
>>> On 12.10.20 19:43, Andrey Shinkevich wrote:
>>>> If the flag BDRV_REQ_PREFETCH was set, pass it further to the
>>>> COR-driver to skip unneeded reading. It can be taken into account for
>>>> the COR-algorithms optimization. That check is being made during the
>>>> block stream job by the moment.
>>>>
>>>> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
>>>> ---
[...]
>>>> diff --git a/block/io.c b/block/io.c
>>>> index 11df188..bff1808 100644
>>>> --- a/block/io.c
>>>> +++ b/block/io.c
>>>> @@ -1512,7 +1512,8 @@ static int coroutine_fn
>>>> bdrv_aligned_preadv(BdrvChild *child,
>>>> max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align);
>>>> if (bytes <= max_bytes && bytes <= max_transfer) {
>>>> - ret = bdrv_driver_preadv(bs, offset, bytes, qiov,
>>>> qiov_offset, 0);
>>>> + ret = bdrv_driver_preadv(bs, offset, bytes, qiov, qiov_offset,
>>>> + flags & bs->supported_read_flags);
>>
>>
>> When BDRV_REQ_PREFETCH is passed, qiov may be (and generally should
>> be) NULL. This means, that we can't just drop the flag when call the
>> driver that doesn't support it.
>>
>> Actually, if driver doesn't support the PREFETCH flag we should do
>> nothing.
>>
>>
>>>
>>> Ah, OK. I see. I expected this to be a separate patch. I still wonder
>>> why it isn’t.
>>>
>>
>>
>> Could it be part of patch 07? I mean introduce new field
>> supported_read_flags and handle it in generic code in one patch, prior
>> to implementing support for it in COR driver.
>>
>>
>
> We have to add the supported flags for the COR driver in the same patch.
> Or before handling the supported_read_flags at the generic layer
> (handling zero does not make a sence). Otherwise, the test #216 (where
> the COR-filter is applied) will not pass.
>
> Andrey
I have found a workaround and am going to send all the related patches
as a separate series.
Andrey
next prev parent reply other threads:[~2020-10-22 7:57 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-12 17:43 [PATCH v11 00/13] Apply COR-filter to the block-stream permanently Andrey Shinkevich via
2020-10-12 17:43 ` [PATCH v11 01/13] copy-on-read: Support preadv/pwritev_part functions Andrey Shinkevich via
2020-10-12 17:43 ` [PATCH v11 02/13] copy-on-read: add filter append/drop functions Andrey Shinkevich via
2020-10-14 10:44 ` Max Reitz
2020-10-14 14:28 ` Andrey Shinkevich
2020-10-14 16:26 ` Max Reitz
2020-10-12 17:43 ` [PATCH v11 03/13] qapi: add filter-node-name to block-stream Andrey Shinkevich via
2020-10-12 17:43 ` [PATCH v11 04/13] copy-on-read: pass overlay base node name to COR driver Andrey Shinkevich via
2020-10-14 11:09 ` Max Reitz
2020-10-14 11:57 ` Max Reitz
2020-10-14 14:56 ` Vladimir Sementsov-Ogievskiy
2020-10-14 16:27 ` Max Reitz
2020-10-14 16:08 ` Andrey Shinkevich
2020-10-14 16:18 ` Vladimir Sementsov-Ogievskiy
2020-10-14 16:36 ` Max Reitz
2020-10-12 17:43 ` [PATCH v11 05/13] copy-on-read: limit COR operations to base in " Andrey Shinkevich via
2020-10-14 11:59 ` Max Reitz
2020-10-14 17:43 ` Andrey Shinkevich
2020-10-14 12:01 ` Max Reitz
2020-10-14 18:57 ` Andrey Shinkevich
2020-10-15 15:56 ` Max Reitz
2020-10-15 17:37 ` Andrey Shinkevich
2020-10-16 14:28 ` Vladimir Sementsov-Ogievskiy
2020-10-12 17:43 ` [PATCH v11 06/13] block: modify the comment for BDRV_REQ_PREFETCH flag Andrey Shinkevich via
2020-10-14 12:22 ` Max Reitz
2020-10-14 15:04 ` Vladimir Sementsov-Ogievskiy
2020-10-14 19:57 ` Andrey Shinkevich
2020-10-12 17:43 ` [PATCH v11 07/13] block: include supported_read_flags into BDS structure Andrey Shinkevich via
2020-10-14 12:31 ` Max Reitz
2020-10-12 17:43 ` [PATCH v11 08/13] copy-on-read: add support for BDRV_REQ_PREFETCH to COR-filter Andrey Shinkevich via
2020-10-14 12:40 ` Max Reitz
2020-10-12 17:43 ` [PATCH v11 09/13] copy-on-read: skip non-guest reads if no copy needed Andrey Shinkevich via
2020-10-14 12:51 ` Max Reitz
2020-10-14 15:22 ` Vladimir Sementsov-Ogievskiy
2020-10-14 16:30 ` Max Reitz
2020-10-14 16:39 ` Vladimir Sementsov-Ogievskiy
2020-10-15 15:49 ` Max Reitz
2020-10-21 20:43 ` Andrey Shinkevich
2020-10-22 7:50 ` Andrey Shinkevich [this message]
2020-10-22 8:56 ` Vladimir Sementsov-Ogievskiy
2020-10-14 20:49 ` Andrey Shinkevich
2020-10-12 17:43 ` [PATCH v11 10/13] stream: skip filters when writing backing file name to QCOW2 header Andrey Shinkevich via
2020-10-14 15:02 ` Max Reitz
2020-10-14 15:40 ` Vladimir Sementsov-Ogievskiy
2020-10-12 17:43 ` [PATCH v11 11/13] stream: mark backing-file argument as deprecated Andrey Shinkevich via
2020-10-14 15:03 ` Max Reitz
2020-10-14 15:43 ` Vladimir Sementsov-Ogievskiy
2020-10-15 9:01 ` Andrey Shinkevich
2020-10-12 17:43 ` [PATCH v11 12/13] stream: remove unused backing-file name parameter Andrey Shinkevich via
2020-10-14 15:05 ` Max Reitz
2020-10-12 17:43 ` [PATCH v11 13/13] block: apply COR-filter to block-stream jobs Andrey Shinkevich via
2020-10-14 16:24 ` Max Reitz
2020-10-15 17:16 ` Andrey Shinkevich
2020-10-16 15:06 ` Andrey Shinkevich
2020-10-16 15:45 ` Vladimir Sementsov-Ogievskiy
2020-10-20 19:43 ` Andrey Shinkevich
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