From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH] virtio_blk: merge S/G list entries by default Date: Sun, 07 Sep 2014 12:18:41 +0200 Message-ID: <540C3101.40701@redhat.com> References: <1410044994-14943-1-git-send-email-hch@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1410044994-14943-1-git-send-email-hch@lst.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Christoph Hellwig , Rusty Russell , "Michael S. Tsirkin" Cc: Jens Axboe , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org Il 07/09/2014 01:09, Christoph Hellwig ha scritto: > Most virtio setups have a fairly limited number of ring entries available. Are you disabling indirect descriptors? With indirect descriptors entry merging doesn't buy you any more space, so perhaps you can key the flag off the availability of VIRTIO_RING_F_INDIRECT_DESC. Paolo > Enable S/G entry merging by default to fit into less of them. This restores > the behavior at time of the virtio-blk blk-mq conversion, which was changed > by commit "block: add queue flag for disabling SG merging" which made the > behavior optional, but didn't update the existing drivers to keep their > previous behavior.