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[PATCH v5 0/6] block: seriously improve savevm performance
From: |
Denis V. Lunev |
Subject: |
[PATCH v5 0/6] block: seriously improve savevm performance |
Date: |
Fri, 19 Jun 2020 13:07:02 +0300 |
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.
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 v4:
- added patch 4 with blk_save_vmstate() cleanup
- added R-By
- bdrv_flush_vmstate -> bdrv_finalize_vmstate
- fixed return code of bdrv_co_do_save_vmstate
- fixed typos in comments (Eric, thanks!)
- fixed patchew warnings
Changes from v3:
- rebased to master
- added patch 3 which removes aio_task_pool_wait_one()
- added R-By to patch 1
- patch 4 is rewritten via bdrv_run_co
- error path in blk_save_vmstate() is rewritten to call bdrv_flush_vmstate
unconditionally
- added some comments
- fixes initialization in bdrv_co_vmstate_save_task_entry as suggested
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>
- [PATCH v5 0/6] block: seriously improve savevm performance,
Denis V. Lunev <=
- [PATCH 4/6] block/block-backend: remove always true check from blk_save_vmstate, Denis V. Lunev, 2020/06/19
- [PATCH 3/6] block/aio_task: drop aio_task_pool_wait_one() helper, Denis V. Lunev, 2020/06/19
- [PATCH 2/6] block/aio_task: allow start/wait task from any coroutine, Denis V. Lunev, 2020/06/19
- [PATCH 1/6] migration/savevm: respect qemu_fclose() error code in save_snapshot(), Denis V. Lunev, 2020/06/19
- [PATCH 6/6] block/io: improve savevm performance, Denis V. Lunev, 2020/06/19
- [PATCH 5/6] block, migration: add bdrv_finalize_vmstate helper, Denis V. Lunev, 2020/06/19
- Re: [PATCH v5 0/6] block: seriously improve savevm performance, no-reply, 2020/06/19
- [PATCH 7/6] block/io: improve loadvm performance, Denis V. Lunev, 2020/06/22