Re: [Qemu-devel] [PATCH v2] Improve accuracy of block migration bandwidth calculation

[Kevin Wolf <kwolf@redhat.com>]

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 <avishay@il.ibm.com>

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