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Date: Wed, 18 May 2016 13:24:57 -0500 (CDT)
From: Christoph Lameter <cl@linux.com>
Subject: Re: [RFC v1 2/2] mm: SLUB Freelist randomization
In-Reply-To: <1463594175-111929-3-git-send-email-thgarnie@google.com>
Message-ID: <alpine.DEB.2.20.1605181323260.14349@east.gentwo.org>
References: <1463594175-111929-1-git-send-email-thgarnie@google.com> <1463594175-111929-3-git-send-email-thgarnie@google.com>
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To: Thomas Garnier <thgarnie@google.com>
Cc: Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Andrew Morton <akpm@linux-foundation.org>, "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>, Pranith Kumar <bobby.prani@gmail.com>, David Howells <dhowells@redhat.com>, Tejun Heo <tj@kernel.org>, Johannes Weiner <hannes@cmpxchg.org>, David Woodhouse <David.Woodhouse@intel.com>, Petr Mladek <pmladek@suse.com>, Kees Cook <keescook@chromium.org>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, gthelen@google.com, kernel-hardening@lists.openwall.com

0.On Wed, 18 May 2016, Thomas Garnier wrote:

> slab_test, before:
> 10000 times kmalloc(8) -> 67 cycles kfree -> 101 cycles
> 10000 times kmalloc(16) -> 68 cycles kfree -> 109 cycles
> 10000 times kmalloc(32) -> 76 cycles kfree -> 119 cycles
> 10000 times kmalloc(64) -> 88 cycles kfree -> 114 cycles

> After:
> 10000 times kmalloc(8) -> 60 cycles kfree -> 74 cycles
> 10000 times kmalloc(16) -> 63 cycles kfree -> 78 cycles
> 10000 times kmalloc(32) -> 72 cycles kfree -> 85 cycles
> 10000 times kmalloc(64) -> 91 cycles kfree -> 99 cycles

Erm... The fastpath was not touched and the tests primarily exercise the
fastpath. This is likely some artifact of code placement by the compiler?

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