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Re: [Qemu-devel] [PATCH v5 0/8] Add metadata overlap checks

From: Stefan Hajnoczi
Subject: Re: [Qemu-devel] [PATCH v5 0/8] Add metadata overlap checks
Date: Fri, 20 Sep 2013 12:32:02 +0200
User-agent: Mutt/1.5.21 (2010-09-15)

On Thu, Sep 19, 2013 at 05:07:56PM +0200, Max Reitz wrote:
> As far as I understand, the I/O speed (the duration of an I/O
> operation) should be pretty much the same for all scenarios,
> however, the latency is the value in question (since the overlap
> checks should affect the latency only).

The other value to look at is the host CPU consumption per I/O.  In
other words, the CPU overhead added by performing the extra checks:

  efficiency = avg throughput / avg cpu utilization

Once CPU consumption reaches 100% the workload is CPU-bound and we have
a bottleneck.

Hopefully the efficiency doesn't change noticably either, then we know
there is no big impact from the extra checks.


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