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Date: Sat, 31 Mar 2012 00:18:36 +0200
From: Andi Kleen <andi@firstfloor.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
        Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
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Subject: Re: [PATCH RFC V6 0/11] Paravirtualized ticketlocks
Message-ID: <20120330221836.GN17822@one.firstfloor.org>
References: <20120321102041.473.61069.sendpatchset@codeblue.in.ibm.com> <4F7616F5.4070000@zytor.com> <alpine.LFD.2.02.1203302333560.2542@ionos>
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> So if a guest exits due to an external event it's easy to inspect the
> state of that guest and avoid to schedule away when it was interrupted
> in a spinlock held section. That guest/host shared state needs to be

On a large system under high contention sleeping can perform surprisingly
well. pthread mutexes have a tendency to beat kernel spinlocks there.
So avoiding sleeping locks completely (that is what pv locks are
essentially) is not necessarily that good.

Your proposal is probably only a good idea on low contention
and relatively small systems.

-Andi
-- 
ak@linux.intel.com -- Speaking for myself only.