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Date: Mon, 25 Nov 2013 17:02:27 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1.8 5/6] qemu-img: add option to align
 writes to cluster_sectors during convert
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To: Peter Lieven <pl@kamp.de>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com

Il 25/11/2013 16:55, Peter Lieven ha scritto:
>>
> chaning sparse_size from 65536 to 1048576 about 5% performance decrease...
> 
> lieven@lieven-pc:~/git/qemu$ time ./qemu-img convert -pp -m 15728640 -S
> 1048576 /tmp/VC-Ubuntu-LTS-12.04.2-64bit.qcow2
> iscsi://172.21.200.45/iqn.2001-05.com.equallogic:0-8a0906-9d95c510a-344001d54795289f-2012-r2-1-7-0/0
> 
> 40980480 of 40980480 sectors converted.
> 
> real    0m29.263s
> user    0m7.544s
> sys    0m1.636s
> lieven@lieven-pc:~/git/qemu$ time ./qemu-img convert -pp -m 15728640 -S
> 4096 /tmp/VC-Ubuntu-LTS-12.04.2-64bit.qcow2
> iscsi://172.21.200.45/iqn.2001-05.com.equallogic:0-8a0906-9d95c510a-344001d54795289f-2012-r2-1-7-0/0
> 
> 40980480 of 40980480 sectors converted.
> 
> real    0m28.169s
> user    0m7.792s
> sys    0m1.516s
> lieven@lieven-pc:~/git/qemu$ time ./qemu-img convert -pp -m 15728640 -S
> 65536 /tmp/VC-Ubuntu-LTS-12.04.2-64bit.qcow2
> iscsi://172.21.200.45/iqn.2001-05.com.equallogic:0-8a0906-9d95c510a-344001d54795289f-2012-r2-1-7-0/0
> 
> 40980480 of 40980480 sectors converted.
> 
> real    0m27.643s
> user    0m7.644s
> sys    0m1.520s
> 
> i wouldn't go over 64k until we fully understand which impact it has.

I agree.

Paolo