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[Xen-ia64-devel] [PATCH] Fix unaligned reference of QEMU

  • To: <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "Duan, Ronghui" <ronghui.duan@xxxxxxxxx>
  • Date: Tue, 21 Aug 2007 14:58:21 +0800
  • Delivery-date: Mon, 20 Aug 2007 23:58:43 -0700
  • List-id: Discussion of the ia64 port of Xen <xen-ia64-devel.lists.xensource.com>
  • Thread-index: AcfjwKk70lBtf1BdQMefEjPWWrrF5A==
  • Thread-topic: [Xen-ia64-devel] [PATCH] Fix unaligned reference of QEMU

Hi

In current changeset.,qemu copy data uses memcpy_words, which copies 4 bytes at once if the length is larger than 4. This causes unaligned reference and leads to a performance downgrade. The issue met in rtl8139 emulator. This patch fixes it.

 

Send Package from guest

Version                size           speed          time 

Original                226MB     1.3MB/s        2:54

memcpy              226MB     2.8MB/s        1:22

Receive Package

Version                size           speed         time 

Original                226MB     1.7MB/s        2:10

memcpy               226MB     6.0MB/s        38 s

 

Thanks

 

Signed-off-by: Duan Ronghui   Ronghui.duan@xxxxxxxxx

 

 

Attachment: memcpy_words.patch
Description: memcpy_words.patch

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