linux-kernel - RE: [PATCH] lockref: remove cpu

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Message-ID: <3908561D78D1C84285E8C5FCA982C28F31CDCDB2@ORSMSX106.amr.corp.intel.com>
Date:	Thu, 5 Sep 2013 19:56:39 +0000
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Heiko Carstens <heiko.carstens@...ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] lockref: remove cpu_relax() again

> That said, another thing that strikes me is that you have 32 CPU
> threads, and the stupid test-program I sent out had MAX_THREADS set to
> 16.  Did you change that? Becuase if not, then some of the extreme
> performance profile might be about how the threads get scheduled on
> your machine (HT threads vs full cores etc).

I'll try to get new numbers with 32 threads[*] - but even if they look good, I'd
be upset about the 16 thread case being worse with the cmpxchg/no-cpu-relax
case than the original code.

-Tony

[*] probably not till tomorrow