linux-kernel - Re: [PATCH -v7][RFC]: mutex: implement adaptive spinning

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Message-ID: <alpine.LRH.1.10.0901091815140.24105@twin.jikos.cz>
Date:	Fri, 9 Jan 2009 18:40:31 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Chris Mason <chris.mason@...cle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...e.hu>, paulmck@...ux.vnet.ibm.com,
	Gregory Haskins <ghaskins@...ell.com>,
	Matthew Wilcox <matthew@....cx>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-btrfs <linux-btrfs@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Nick Piggin <npiggin@...e.de>,
	Peter Morreale <pmorreale@...ell.com>,
	Sven Dietrich <SDietrich@...ell.com>
Subject: Re: [PATCH -v7][RFC]: mutex: implement adaptive spinning

On Thu, 8 Jan 2009, Peter Zijlstra wrote:

> > Well, at least we do unless you enable that broken paravirt support. 
> > I'm not at all clear on why CONFIG_PARAVIRT wants to use inferior 
> > locks, but I don't much care.
> Because the virtual cpu that has the ticket might not get scheduled for
> a while, even though another vcpu with a spinner is scheduled.
> The whole (para)virt is a nightmare in that respect.

Hmm, are we in fact really using byte locks in CONFIG_PARAVIRT situation? 
Where are we actually setting pv_lock_ops.spin_lock pointer to point to 
__byte_spin_lock?

Such initialization seems to happen only in paravirt_use_bytelocks() 
function, but my blind eyes prevent me from finding a callsite from which 
this function would eventually get called.

-- 
Jiri Kosina
SUSE Labs

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