From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Coquelin Subject: Re: [PATCH v7 0/7] vhost: optimize mergeable Rx path Date: Tue, 18 Oct 2016 16:53:55 +0200 Message-ID: <7f04d548-e39a-e9bb-c918-adeb994002d2@redhat.com> References: <1474336817-22683-1-git-send-email-zhihong.wang@intel.com> <1476437678-7102-1-git-send-email-yuanhan.liu@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: Jianbo Liu To: Yuanhan Liu , dev@dpdk.org Return-path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id 479ED2E41 for ; Tue, 18 Oct 2016 16:53:59 +0200 (CEST) In-Reply-To: <1476437678-7102-1-git-send-email-yuanhan.liu@linux.intel.com> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Hi Yuanhan, On 10/14/2016 11:34 AM, Yuanhan Liu wrote: > This is a new set of patches to optimize the mergeable Rx code path. > No refactoring (rewrite) was made this time. It just applies some > findings from Zhihong (kudos to him!) that could improve the mergeable > Rx path on the old code. > > The two major factors that could improve the performance greatly are: > > - copy virtio header together with packet data. This could remove > the buubbles between the two copy to optimize the cache access. > > This is implemented in patch 2 "vhost: optimize cache access" > > - shadow used ring update and update them at once > > The basic idea is to update used ring in a local buffer and flush > them to the virtio used ring at once in the end. Again, this is > for optimizing the cache access. > > This is implemented in patch 5 "vhost: shadow used ring update" > > The two optimizations could yield 40+% performance in micro testing > and 20+% in PVP case testing with 64B packet size. > > Besides that, there are some tiny optimizations, such as prefetch > avail ring (patch 6) and retrieve avail head once (patch 7). > > Note: the shadow used ring tech could also be applied to the non-mrg > Rx path (and even the dequeu) path. I didn't do that for two reasons: > > - we already update used ring in batch in both path: it's not shadowed > first though. > > - it's a bit too late too make many changes at this stage: RC1 is out. > > Please help testing. I tested the following use-cases without noticing any functional problems: - Windows Guests (mergeable ON & OFF, indirect disabled): ping other VM - Linux guests with Kernel driver (mergeable ON & OFF, indirect OFF): iperf between 2 VMs - Linux guest with Virtio PMD (mergeable ON & OFF): testpmd txonly on host, rxonly on guest. Feel free to add my: Tested-by: Maxime Coquelin Thanks, Maxime