From: "Andi Kleen" <andi@firstfloor.org>
To: miaox@cn.fujitsu.com
Cc: "Andi Kleen" <andi@firstfloor.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Ingo Molnar" <mingo@elte.hu>, "Theodore Ts'o" <tytso@mit.edu>,
"Chris Mason" <chris.mason@oracle.com>,
"Linux Kernel" <linux-kernel@vger.kernel.org>,
"Linux Btrfs" <linux-btrfs@vger.kernel.org>,
"Linux Ext4" <linux-ext4@vger.kernel.org>
Subject: Re: [PATCH] x86_64/lib: improve the performance of memmove
Date: Thu, 16 Sep 2010 08:48:25 +0200 (CEST) [thread overview]
Message-ID: <56957.91.60.149.91.1284619705.squirrel@www.firstfloor.org> (raw)
> When the dest and the src do overlap and the memory area is large, memmove
> of
> x86_64 is very inefficient, and it led to bad performance, such as btrfs's
> file
> deletion performance. This patch improved the performance of memmove on
> x86_64
> by using __memcpy_bwd() instead of byte copy when doing large memory area
> copy
> (len > 64).
I still don't understand why you don't simply use a backwards
string copy (with std) ? That should be much simpler and
hopefully be as optimized for kernel copies on recent CPUs.
-Andi
next reply other threads:[~2010-09-16 6:48 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-16 6:48 Andi Kleen [this message]
2010-09-16 7:16 ` Miao Xie
2010-09-16 8:40 ` Andi Kleen
2010-09-16 9:29 ` Miao Xie
2010-09-16 10:11 ` Andi Kleen
2010-09-16 10:47 ` Miao Xie
2010-09-16 11:47 ` Miao Xie
2010-09-17 0:55 ` ykzhao
2010-09-17 3:37 ` Miao Xie
-- strict thread matches above, loose matches on Subject: below --
2010-09-16 12:13 George Spelvin
2010-09-16 6:31 Miao Xie
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