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

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Message-ID: <4FF2F417.2010209@redhat.com>
Date:	Tue, 03 Jul 2012 15:31:03 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	Asias He <asias@...hat.com>, 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

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. :)

Paolo

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