From: "Michael S. Tsirkin" <mst@redhat.com>
To: kvm@vger.kernel.org
Cc: gleb@redhat.com
Subject: Re: 8bf00a529967dafbbb210b377c38a15834d1e979 - performance regression?
Date: Mon, 4 Nov 2013 21:30:42 +0200 [thread overview]
Message-ID: <20131104193042.GA28102@redhat.com> (raw)
In-Reply-To: <20131031002146.GA28569@redhat.com>
On Thu, Oct 31, 2013 at 02:21:46AM +0200, Michael S. Tsirkin wrote:
> commit 8bf00a529967dafbbb210b377c38a15834d1e979:
> " KVM: VMX: add support for switching of PERF_GLOBAL_CTRL " was
> as far as I can tell supposed to bring about performance improvement
> on hardware that supports it?
> Instead it seems to make the typical case (not running guest
> under perf) a bit slower than it used to be.
> the cost of VMexit goes up by about 50 cycles
> on sandy bridge where the optimization in question
> actually is activated.
>
> Why that's not a large regression, it's a far cry from
> actually helping performance.
>
> So are we better off not using this feature?
> What kind of workload is improved by this change?
Ping.
Let's revert 8bf00a529967dafbbb210b377c38a15834d1e979?
I see a small performance gain from reverting it ...
--
MST
next prev parent reply other threads:[~2013-11-04 19:27 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-31 0:21 8bf00a529967dafbbb210b377c38a15834d1e979 - performance regression? Michael S. Tsirkin
2013-10-31 7:48 ` Gleb Natapov
2013-11-04 20:11 ` Michael S. Tsirkin
2013-11-04 20:13 ` Gleb Natapov
2013-11-04 20:33 ` Michael S. Tsirkin
2013-11-04 20:44 ` Gleb Natapov
2013-11-05 10:18 ` Michael S. Tsirkin
2013-11-05 10:22 ` Gleb Natapov
2013-11-05 11:20 ` Gleb Natapov
2013-11-05 16:36 ` Michael S. Tsirkin
2013-11-05 16:40 ` Gleb Natapov
2013-11-05 16:44 ` Michael S. Tsirkin
2013-11-18 19:04 ` Michael S. Tsirkin
2013-11-18 19:09 ` Gleb Natapov
2013-11-18 19:37 ` Michael S. Tsirkin
2013-11-04 19:30 ` Michael S. Tsirkin [this message]
2013-11-04 19:39 ` Gleb Natapov
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