From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH 3/3] virtio-blk: Add bio-based IO path for virtio-blk Date: Tue, 03 Jul 2012 15:31:03 +0200 Message-ID: <4FF2F417.2010209@redhat.com> References: <1340002390-3950-1-git-send-email-asias@redhat.com> <1340002390-3950-4-git-send-email-asias@redhat.com> <87hau9yse7.fsf@rustcorp.com.au> <4FDEE0CB.1030505@redhat.com> <87zk81x7dp.fsf@rustcorp.com.au> <4FDF0DA7.40604@redhat.com> <1340019575.22848.2.camel@lappy> <4FDFE926.7030309@redhat.com> <87r4svxcjw.fsf@rustcorp.com.au> <4FF10B31.60609@redhat.com> <8762a6y89v.fsf@rustcorp.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Asias He , kvm@vger.kernel.org, "Michael S. Tsirkin" , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Sasha Levin , Christoph Hellwig To: Rusty Russell Return-path: In-Reply-To: <8762a6y89v.fsf@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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