linux-kernel - Re: [PATCH v7 1/4] qrwlock: A queue read/write lock implementation

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Message-ID: <87zjnxlxtg.fsf@tassilo.jf.intel.com>
Date:	Wed, 18 Dec 2013 12:16:11 -0800
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Waiman Long <Waiman.Long@...com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>,
	"linux-arch\@vger.kernel.org" <linux-arch@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michel Lespinasse <walken@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	George Spelvin <linux@...izon.com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Aswin Chandramouleeswaran <aswin@...com>,
	Scott J Norton <scott.norton@...com>
Subject: Re: [PATCH v7 1/4] qrwlock: A queue read/write lock implementation

Peter Zijlstra <peterz@...radead.org> writes:

> On Wed, Dec 18, 2013 at 11:38:29AM -0800, Andi Kleen wrote:
>> (maybe it would be time to get rid of the patchable LOCK though?)
>
> With the argument that Intel simply doesn't ship UP chips anymore, with
> the exception of quark which should probably run custom UP kernels due
> to size constraints anyway?

That, and:

- Anything with a single core only has very fast LOCK
- LOCK generally became much faster everywhere.
- The original reason was for single cpu VM guests, but even those
should increasingly have at least two VCPUs.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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