From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH 0/9] kvm tools, qcow: Improve QCOW performance
Date: Sun, 10 Jul 2011 19:15:43 +0200
Message-ID: <20110710171543.GA19513@elte.hu>
References: <1310216563-17503-1-git-send-email-penberg@kernel.org>
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Cc: kvm@vger.kernel.org, Asias He <asias.hejun@gmail.com>,
	Cyrill Gorcunov <gorcunov@gmail.com>,
	Prasad Joshi <prasadjoshi124@gmail.com>,
	Sasha Levin <levinsasha928@gmail.com>
To: Pekka Enberg <penberg@kernel.org>
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* Pekka Enberg <penberg@kernel.org> wrote:

> This series fixes QCOW locking issues and implements delayed metadata writeout.
> This improves performance of writeout to QCOW2 images that don't have clusters
> and L2 tables allocated on-disk.
> 
> I tested the series by running 
> 
>   mount -t ext4 /dev/vdb /mnt
>   dd if=/dev/zero of=/mnt/tmp
> 
> in the guest multiple times for fresly generated QCOW2 image:
> 
>   dd if=/dev/zero of=fs.ext4 bs=1024k count=512 && mkfs.ext4 -F fs.ext4 && qemu-img convert -O qcow2 fs.ext4 fs.qcow2
> 
> which causes worst-case behavior for the current code.
> 
> Before:
> 
>   [ seekwatcher: http://userweb.kernel.org/~penberg/kvm-qcow-delayed/kvm-qcow2-master.png ]
> 
>   511229952 bytes (511 MB) copied, 19.906 s, 25.7 MB/s
>   511229952 bytes (511 MB) copied, 20.3168 s, 25.2 MB/s
>   511229952 bytes (511 MB) copied, 20.8078 s, 24.6 MB/s
>   511229952 bytes (511 MB) copied, 21.0889 s, 24.2 MB/s
>   511229952 bytes (511 MB) copied, 20.7833 s, 24.6 MB/s
>   511229952 bytes (511 MB) copied, 20.7536 s, 24.6 MB/s
>   511229952 bytes (511 MB) copied, 20.0312 s, 25.5 MB/s
> 
> After:
> 
>   [ seekwatcher: http://userweb.kernel.org/~penberg/kvm-qcow-delayed/kvm-qcow2-delayed.png ]
> 
>   511229952 bytes (511 MB) copied, 7.68312 s, 66.5 MB/s
>   511229952 bytes (511 MB) copied, 7.54065 s, 67.8 MB/s
>   511229952 bytes (511 MB) copied, 9.34749 s, 54.7 MB/s
>   511229952 bytes (511 MB) copied, 9.2421 s, 55.3 MB/s
>   511229952 bytes (511 MB) copied, 9.9364 s, 51.5 MB/s
>   511229952 bytes (511 MB) copied, 10.0337 s, 51.0 MB/s
>   511229952 bytes (511 MB) copied, 9.39502 s, 54.4 MB/s

Just wondering, how does Qemu perform on the same system using the 
same image, with comparable settings?

Thanks,

	Ingo