From: Rik van Riel <riel@redhat.com>
To: Chegu Vinod <chegu_vinod@hp.com>
Cc: kvm@vger.kernel.org, Gleb Natapov <gleb@redhat.com>
Subject: Re: Performance of 40-way guest running 2.6.32-220 (RHEL6.2) vs. 3.3.1 OS
Date: Thu, 12 Apr 2012 14:21:06 -0400 [thread overview]
Message-ID: <4F871D12.3060006@redhat.com> (raw)
In-Reply-To: <loom.20120411T183827-108@post.gmane.org>
On 04/11/2012 01:21 PM, Chegu Vinod wrote:
>
> Hello,
>
> While running an AIM7 (workfile.high_systime) in a single 40-way (or a single
> 60-way KVM guest) I noticed pretty bad performance when the guest was booted
> with 3.3.1 kernel when compared to the same guest booted with 2.6.32-220
> (RHEL6.2) kernel.
> For the 40-way Guest-RunA (2.6.32-220 kernel) performed nearly 9x better than
> the Guest-RunB (3.3.1 kernel). In the case of 60-way guest run the older guest
> kernel was nearly 12x better !
> Turned on function tracing and found that there appears to be more time being
> spent around the lock code in the 3.3.1 guest when compared to the 2.6.32-220
> guest.
Looks like you may be running into the ticket spinlock
code. During the early RHEL 6 days, Gleb came up with a
patch to automatically disable ticket spinlocks when
running inside a KVM guest.
IIRC that patch got rejected upstream at the time,
with upstream developers preferring to wait for a
"better solution".
If such a better solution is not on its way upstream
now (two years later), maybe we should just merge
Gleb's patch upstream for the time being?
next prev parent reply other threads:[~2012-04-12 18:20 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-11 17:21 Performance of 40-way guest running 2.6.32-220 (RHEL6.2) vs. 3.3.1 OS Chegu Vinod
2012-04-12 18:21 ` Rik van Riel [this message]
2012-04-16 3:04 ` Chegu Vinod
2012-04-16 12:18 ` Gleb Natapov
2012-04-16 14:44 ` Chegu Vinod
2012-04-17 9:49 ` Gleb Natapov
2012-04-17 13:25 ` Chegu Vinod
2012-04-19 4:44 ` Chegu Vinod
2012-04-19 6:01 ` Gleb Natapov
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