From: Dave Hansen <dave@sr71.net>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
cl@linux-foundation.org, penberg@kernel.org, mpm@selenic.com,
pshelar@nicira.com, Wu Fengguang <fengguang.wu@intel.com>
Subject: Re: [PATCH] mm: slub: fix page->_count corruption (again)
Date: Tue, 28 Jan 2014 15:52:47 -0800 [thread overview]
Message-ID: <52E842CF.7090102@sr71.net> (raw)
In-Reply-To: <20140128152956.d5659f56ae279856731a1ac5@linux-foundation.org>
On 01/28/2014 03:29 PM, Andrew Morton wrote:
> On Tue, 28 Jan 2014 15:17:22 -0800 Dave Hansen <dave@sr71.net> wrote:
> This code is borderline insane.
No argument here.
> Yes, struct page is special and it's worth spending time and doing
> weird things to optimise it. But sheesh.
>
> An alternative is to make that cmpxchg quietly go away. Is it more
> trouble than it is worth?
It has measurable performance benefits, and the benefits go up as the
cost of en/disabling interrupts goes up (like if it takes you a hypercall).
Fengguang, could you run a set of tests for the top patch in this branch
to see if we'd be giving much up by axing the code?
https://github.com/hansendc/linux/tree/slub-nocmpxchg-for-Fengguang-20140128
I was talking with one of the distros about turning it off as well.
They mentioned that they saw a few performance regressions when it was
turned off. I'll share details when I get them.
next prev parent reply other threads:[~2014-01-28 23:52 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-28 23:17 [PATCH] mm: slub: fix page->_count corruption (again) Dave Hansen
2014-01-28 23:29 ` Andrew Morton
2014-01-28 23:52 ` Dave Hansen [this message]
2014-01-29 6:43 ` Fengguang Wu
2014-01-29 8:13 ` Fengguang Wu
2014-01-29 8:30 ` David Rientjes
2014-02-01 12:00 ` Fengguang Wu
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