From: Andi Kleen <andi@firstfloor.org>
To: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Hitoshi Mitake <mitake.hitoshi@gmail.com>,
Andi Kleen <andi@firstfloor.org>,
linux-kernel@vger.kernel.org, Andi Kleen <ak@linux.intel.com>,
h.mitake@gmail.com, kirill.shutemov@linux.intel.com
Subject: Re: [PATCH] perf, tools, bench: Fix memcpy benchmark for large sizes v2
Date: Mon, 22 Jul 2013 21:32:43 +0200 [thread overview]
Message-ID: <20130722193243.GP6123@two.firstfloor.org> (raw)
In-Reply-To: <20130722160045.GG2157@ghostprotocols.net>
On Mon, Jul 22, 2013 at 01:00:45PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Sat, Jul 20, 2013 at 12:57:27AM +0900, Hitoshi Mitake escreveu:
> > At Thu, 18 Jul 2013 15:43:18 -0700, Andi Kleen wrote:
> > > glibc calloc() has an optimization to not explicitely memset()
> > > very large calloc allocations that just came from mmap(),
> > > because they are known to be zero.
>
> > > This could result in the perf memcpy benchmark reading only from
> > > the zero page, which gives unrealistic results.
>
> > > Always call memset explicitly on the source area to avoid this problem.
>
> > > +++ b/tools/perf/bench/mem-memcpy.c
> > > @@ -115,8 +115,10 @@ static void alloc_mem(void **dst, void **src, size_t length)
> > > *src = zalloc(length);
> > > - if (!src)
> > > + if (!*src)
>
> > In the latest mem-memcpy.c, this if (!src) is already fixed as if
> > (!*src). This modification makes applying fail.
>
> I fixed this up, please take a look at:
>
> https://git.kernel.org/cgit/linux/kernel/git/acme/linux.git/commit/?h=perf/core&id=a198996c7afae0097c67a61851f19863e59697b2
>
> https://git.kernel.org/cgit/linux/kernel/git/acme/linux.git/log/?h=perf/core
Looks good. Thanks.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
prev parent reply other threads:[~2013-07-22 19:32 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-18 22:43 [PATCH] perf, tools, bench: Fix memcpy benchmark for large sizes v2 Andi Kleen
2013-07-19 15:57 ` Hitoshi Mitake
2013-07-19 17:35 ` Andi Kleen
2013-07-22 16:00 ` Arnaldo Carvalho de Melo
2013-07-22 19:32 ` Andi Kleen [this message]
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