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Date: Thu, 16 Sep 2010 08:48:25 +0200 (CEST) From: "Andi Kleen" <andi@...stfloor.org> To: miaox@...fujitsu.com Cc: "Andi Kleen" <andi@...stfloor.org>, "Andrew Morton" <akpm@...ux-foundation.org>, "Ingo Molnar" <mingo@...e.hu>, "Theodore Ts'o" <tytso@....edu>, "Chris Mason" <chris.mason@...cle.com>, "Linux Kernel" <linux-kernel@...r.kernel.org>, "Linux Btrfs" <linux-btrfs@...r.kernel.org>, "Linux Ext4" <linux-ext4@...r.kernel.org> Subject: Re: [PATCH] x86_64/lib: improve the performance of memmove > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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