linux-kernel - Re: [rfc][patch] queued spinlocks (i386)

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Message-ID: <Pine.LNX.4.64.0703291942280.1199@alien.or.mcafeemobile.com>
Date:	Thu, 29 Mar 2007 19:43:04 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Nick Piggin <npiggin@...e.de>
cc:	Ingo Molnar <mingo@...e.hu>, Nikita Danilov <nikita@...sterfs.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ravikiran G Thirumalai <kiran@...lex86.org>
Subject: Re: [rfc][patch] queued spinlocks (i386)

On Fri, 30 Mar 2007, Nick Piggin wrote:

> > I slightly modified it to use cycles:
> > 
> > http://www.xmailserver.org/qspins.c
> 
> Slightly more than slightly ;)
> 
> You want to have a delay _outside_ the critical section as well, for
> multi-thread tests, otherwise the releasing CPU often just retakes
> the lock (in the unqueued lock case). As I said, most kernel code
> should _not_ be dropping and retaking locks.

Yeah. ATM it mostly does double-takes.



- Davide


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