From mboxrd@z Thu Jan 1 00:00:00 1970 From: Seth Forshee Subject: Performance regression with virtio_net Date: Thu, 27 Jul 2017 12:09:42 -0500 Message-ID: <20170727170942.ub24lwgrl3x2outp@ubuntu-hedt> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: virtualization@lists.linux-foundation.org, netdev@vger.kernel.org To: "Michael S. Tsirkin" , Jason Wang Return-path: Received: from mail-it0-f44.google.com ([209.85.214.44]:33508 "EHLO mail-it0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751122AbdG0RJo (ORCPT ); Thu, 27 Jul 2017 13:09:44 -0400 Received: by mail-it0-f44.google.com with SMTP id v127so2520717itd.0 for ; Thu, 27 Jul 2017 10:09:44 -0700 (PDT) Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: I'm seeing a performance regression with virtio_net that looks to have started in 4.12-rc1. I only see it in one context though, downloading snap packages from the Ubuntu snap store. For example: https://api.snapcraft.io/api/v1/snaps/download/b8X2psL1ryVrPt5WEmpYiqfr5emixTd7_1797.snap which redirects to Internap's CDN. Normally this downloads in a few seconds at ~10 MB/s, but with 4.12 and 4.13 it takes minutes with a rate of ~150 KB/s. Everything else I've tried downloads as normal speeds. I bisected this to 680557cf79f8 "virtio_net: rework mergeable buffer handling". If I revert this on top of 4.13-rc2 (along with other changes needed to successfully revert it) speeds return to normal. Thanks, Seth