[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH v2] Improve accuracy of block migration bandwidt
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH v2] Improve accuracy of block migration bandwidth calculation |
Date: |
Wed, 20 Apr 2011 14:34:49 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.15) Gecko/20101027 Fedora/3.0.10-1.fc12 Thunderbird/3.0.10 |
Am 03.04.2011 10:31, schrieb Avishay Traeger:
>
> Revised patch for improving the accuracy of the block migration bandwidth
> calculation. Thanks a lot to Michael Roth for the input.
>
> For those that missed the original patch, here is the description:
> block_mig_state.total_time is currently the sum of the read request
> latencies. This is not very accurate because block migration uses aio and
> so several requests can be submitted at once. Bandwidth should be computed
> with wall-clock time, not by adding the latencies. In this case,
> "total_time" has a higher value than it should, and so the computed
> bandwidth is lower than it is in reality. This means that migration can
> take longer than it needs to.
> However, we don't want to use pure wall-clock time here. We are computing
> bandwidth in the asynchronous phase, where the migration repeatedly wakes
> up and sends some aio requests. The computed bandwidth will be used for
> synchronous transfer.
>
>
> Avishay
>
>
> Signed-off-by: Avishay Traeger <address@hidden>
Thanks. Fixed line wraps and coding style and applied to the block
branch. Please take care to avoid patch corruption next time - usually
such patches are not fixed manually, but rejected.
Kevin