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Re: Big TCG slowdown when using zstd with aarch64
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From: |
Peter Maydell |
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Subject: |
Re: Big TCG slowdown when using zstd with aarch64 |
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Date: |
Fri, 2 Jun 2023 10:22:28 +0100 |
On Fri, 2 Jun 2023 at 10:10, Daniel P. Berrangé <berrange@redhat.com> wrote:
> I suspect that the zstd logic takes a little bit longer in setup,
> which allows often allows the guest dirty workload to get ahead of
> it, resulting in a huge amount of data to transfer. Every now and
> then the compression code gets ahead of the workload and thus most
> data is zeros and skipped.
>
> IMHO this feels like just another example of compression being largely
> useless. The CPU overhead of compression can't keep up with the guest
> dirty workload, making the supposedly network bandwidth saving irrelevant.
It seems a bit surprising if compression can't keep up with
a TCG guest workload, though...
-- PMM