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Re: [Qemu-devel] [PATCH 00/23] block migration: Fixes, cleanups and spee
From: |
Pierre Riteau |
Subject: |
Re: [Qemu-devel] [PATCH 00/23] block migration: Fixes, cleanups and speedups |
Date: |
Mon, 30 Nov 2009 19:50:03 +0100 |
On 30 nov. 2009, at 19:34, Anthony Liguori wrote:
> Jan Kiszka wrote:
>> This series is a larger rework of the block migration support qemu
>> recently gained. Besides lots of code refactorings the major changes
>> are:
>> - Faster restore due to larger block sizes (even if the target disk is
>> unallocated)
>> - Off-by-one fixes in the block dirty tracking code
>> - Allow for multiple migrations (after cancellation or if migrating
>> into a backup image)
>> - Proper error handling
>> - Progress reporting fixes: report to monitor instead of stdout, report
>> sum of multiple disks
>> - Report disk migration progress via 'info migrate'
>> - Progress report during restore
>>
>> One patch is directly taken from Pierre Riteau queue [1] who happend to
>> work on the some topic the last days, two more are derived from his
>> commits.
>>
>> These patches make block migration usable for us. Still, there are two
>> more major improvements on my wish/todo list:
>> - Respect specified maximum migration downtime (will require tracking
>> of the number of dirty blocks + some coordination with ram migration)
>> - Do not transfere unallocated disk space (also for raw images, ie. add
>> bdrv_is_allocated support for the latter)
>>
>> In an off-list chat, Liran additionally brought up the topic that RAM
>> migration should not start too early so that we avoid re-transmitting
>> dirty pages over and over again while the disk image is slowly beamed
>> over.
>>
>> I hope we can join our efforts to resolve the open topics quickly, the
>> critical ones ideally before the merge window closes.
>>
>
> That really needs to happen no later than the end of this week.
>
> So Pierre/Liran, what do you think about Jan's series?
>
> Regards,
>
> Anthony Liguori
I'm currently testing these patches. Here are a few issues I noticed, before I
forget about them.
- "migrate -d -b tcp:dest:port" works, but "migrate -b -d tcp:dest:port"
doesn't, although "help migrate" doesn't really specify ordering as important.
But anyway I think Liran is working on a new version of the command.
- We use bdrv_aio_readv() to read blocks from the disk. This function
increments rd_bytes and rd_ops, which are reported by "info blockstats". I
don't think this read operations should appear in VM activity, especially if
this interface is used by libvirt to report VM stats (and draw graphs in
virt-manager, etc.). Same for write stats.
- We may need to call bdrv_reset_dirty() _before_ sending the data, to be sure
the block is not rewritten in the meantime (maybe it's an issue only with kvm?)
- I seem to remember that disk images with 0 size are now possible. I'm afraid
we will hit a divide by zero in this case: "progress = completed_sector_sum *
100 / block_mig_state.total_sector_sum;"
Apart from that, it works quite fine. Still a few things to cleanup (e.g.
unused constants) but much better than before.
However, I haven't tested the incremental transfer support at all yet. It's on
my todo list.
--
Pierre Riteau -- http://perso.univ-rennes1.fr/pierre.riteau/
- [Qemu-devel] [PATCH 14/23] block migration: Consolidate block transmission, (continued)
- [Qemu-devel] [PATCH 14/23] block migration: Consolidate block transmission, Jan Kiszka, 2009/11/30
- [Qemu-devel] [PATCH 09/23] Import a simple queue implementation from NetBSD, Jan Kiszka, 2009/11/30
- [Qemu-devel] [PATCH 18/23] block migration: Report overall migration progress, Jan Kiszka, 2009/11/30
- [Qemu-devel] [PATCH 22/23] block migration: Add support for restore progress reporting, Jan Kiszka, 2009/11/30
- [Qemu-devel] [PATCH 10/23] block migration: Switch device and block lists to QSIMPLEQ, Jan Kiszka, 2009/11/30
- [Qemu-devel] [PATCH 07/23] block migration: Avoid indirection of block_mig_state, Jan Kiszka, 2009/11/30
- [Qemu-devel] [PATCH 11/23] block migration: Initialize remaining BlkMigState fields, Jan Kiszka, 2009/11/30
- [Qemu-devel] [PATCH 20/23] block migration: Fix outgoing progress output, Jan Kiszka, 2009/11/30
- [Qemu-devel] [PATCH 04/23] block migration: Rework constants API, Jan Kiszka, 2009/11/30
- Re: [Qemu-devel] [PATCH 00/23] block migration: Fixes, cleanups and speedups, Anthony Liguori, 2009/11/30
- Re: [Qemu-devel] [PATCH 00/23] block migration: Fixes, cleanups and speedups,
Pierre Riteau <=
- Re: [Qemu-devel] [PATCH 00/23] block migration: Fixes, cleanups and speedups, Jan Kiszka, 2009/11/30
- Re: [Qemu-devel] [PATCH 00/23] block migration: Fixes, cleanups and speedups, Pierre Riteau, 2009/11/30
- Re: [Qemu-devel] [PATCH 00/23] block migration: Fixes, cleanups and speedups, Jan Kiszka, 2009/11/30
Re: [Qemu-devel] [PATCH 00/23] block migration: Fixes, cleanups and speedups, Jan Kiszka, 2009/11/30