linux-kernel - Re: [PATCH 3/3] virtio-blk: Add bio-based IO path for virtio-blk

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Message-ID: <4FF2FB5D.5030102@redhat.com>
Date:	Tue, 03 Jul 2012 22:02:05 +0800
From:	Asias He <asias@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
CC:	Rusty Russell <rusty@...tcorp.com.au>, kvm@...r.kernel.org,
	"Michael S. Tsirkin" <mst@...hat.com>,
	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org,
	Sasha Levin <levinsasha928@...il.com>,
	Christoph Hellwig <hch@....de>
Subject: Re: [PATCH 3/3] virtio-blk: Add bio-based IO path for virtio-blk

On 07/03/2012 09:31 PM, Paolo Bonzini wrote:
> Il 02/07/2012 08:41, Rusty Russell ha scritto:
>>> With the same workload in guest, the guest fires 200K requests to host
>>> with merges enabled in guest (echo 0 > /sys/block/vdb/queue/nomerges),
>>> while the guest fires 40000K requests to host with merges disabled in
>>> guest (echo 2 > /sys/block/vdb/queue/nomerges). This show that the merge
>>> in block layer reduces the total number of requests fire to host a lot
>>> (40000K / 200K = 20).
>>>
>
> 40000 / 200 is 200, not 20. :)

Crap, I wrote one more zero here. Actually, it is 4000K. So the factor 
is still 4000K/200k = 20 ;-)

-- 
Asias


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