[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH v3 0/4] block: seriously improve savevm performance
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH v3 0/4] block: seriously improve savevm performance |
Date: |
Mon, 15 Jun 2020 13:17:14 +0100 |
User-agent: |
Mutt/1.14.0 (2020-05-02) |
* Denis V. Lunev (den@openvz.org) wrote:
> This series do standard basic things:
> - it creates intermediate buffer for all writes from QEMU migration code
> to QCOW2 image,
> - this buffer is sent to disk asynchronously, allowing several writes to
> run in parallel.
>
> In general, migration code is fantastically inefficent (by observation),
> buffers are not aligned and sent with arbitrary pieces, a lot of time
> less than 100 bytes at a chunk, which results in read-modify-write
> operations with non-cached operations. It should also be noted that all
> operations are performed into unallocated image blocks, which also suffer
> due to partial writes to such new clusters.
It surprises me a little that you're not benefiting from the buffer
internal to qemu-file.c
Dave
> This patch series is an implementation of idea discussed in the RFC
> posted by Denis Plotnikov
> https://lists.gnu.org/archive/html/qemu-devel/2020-04/msg01925.html
> Results with this series over NVME are better than original code
> original rfc this
> cached: 1.79s 2.38s 1.27s
> non-cached: 3.29s 1.31s 0.81s
>
> Changes from v2:
> - code moved from QCOW2 level to generic block level
> - created bdrv_flush_vmstate helper to fix 022, 029 tests
> - added recursive for bs->file in bdrv_co_flush_vmstate (fix 267)
> - fixed blk_save_vmstate helper
> - fixed coroutine wait as Vladimir suggested with waiting fixes from me
>
> Changes from v1:
> - patchew warning fixed
> - fixed validation that only 1 waiter is allowed in patch 1
>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Max Reitz <mreitz@redhat.com>
> CC: Stefan Hajnoczi <stefanha@redhat.com>
> CC: Fam Zheng <fam@euphon.net>
> CC: Juan Quintela <quintela@redhat.com>
> CC: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> CC: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> CC: Denis Plotnikov <dplotnikov@virtuozzo.com>
>
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
- Re: [PATCH 2/4] block/aio_task: allow start/wait task from any coroutine, (continued)
[PATCH 4/4] block/io: improve savevm performance, Denis V. Lunev, 2020/06/11
[PATCH 1/4] migration/savevm: respect qemu_fclose() error code in save_snapshot(), Denis V. Lunev, 2020/06/11
[PATCH 3/4] block, migration: add bdrv_flush_vmstate helper, Denis V. Lunev, 2020/06/11
Re: [PATCH v3 0/4] block: seriously improve savevm performance,
Dr. David Alan Gilbert <=