linux-kernel - Re: [PATCH 13/14] x86/ticketlock: add slowpath logic

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Message-Id: <4D3813E5020000780002D5FA@vpn.id2.novell.com>
Date:	Thu, 20 Jan 2011 09:52:21 +0000
From:	"Jan Beulich" <JBeulich@...ell.com>
To:	"Jeremy Fitzhardinge" <jeremy@...p.org>
Cc:	"Jeremy Fitzhardinge" <jeremy.fitzhardinge@...rix.com>,
	"Eric Dumazet" <dada1@...mosbay.com>, <xiyou.wangcong@...il.com>,
	<suzuki@...ibm.com>, "Peter Zijlstra" <peterz@...radead.org>,
	"Nick Piggin" <npiggin@...nel.dk>, <vatsa@...ux.vnet.ibm.com>,
	"Linux Virtualization" <virtualization@...ts.linux-foundation.org>,
	"Xen-devel" <xen-devel@...ts.xensource.com>,
	"Mathieu Desnoyers" <mathieu.desnoyers@...ymtl.ca>,
	"Avi Kivity" <avi@...hat.com>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 13/14] x86/ticketlock: add slowpath logic

>>> On 19.01.11 at 19:55, Jeremy Fitzhardinge <jeremy@...p.org> wrote:
> On 01/19/2011 10:39 AM, Srivatsa Vaddagiri wrote:
>> I have tested quite extensively with booting a 16-vcpu guest (on a 16-pcpu 
> host)
>> and running kernel compine (with 32-threads). Without this patch, I had
>> difficulty booting/shutting-down successfully (it would hang mid-way).
> 
> Sounds good.  But I like to test with "make -j 100-200" to really give
> things a workout.

Hmm, in my experience, heavily over-committing CPUs (e.g. a
domain with double or more the vCPU-s that the system has
pCPU-s, or the pCPU-s the domain is allowed to run on) is a
much better test for eventual problems in the spin lock code
paths.

Jan

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