From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753178Ab0G3PqV (ORCPT ); Fri, 30 Jul 2010 11:46:21 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.144]:44634 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752022Ab0G3PqQ (ORCPT ); Fri, 30 Jul 2010 11:46:16 -0400 Subject: Re: [RFC PATCH v8 00/16] Provide a zero-copy method on KVM virtio-net. From: Shirley Ma To: Avi Kivity Cc: xiaohui.xin@intel.com, netdev@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mst@redhat.com, mingo@elte.hu, davem@davemloft.net, herbert@gondor.hengli.com.au, jdike@linux.intel.com In-Reply-To: <4C525CD2.5080604@redhat.com> References: <1280402088-5849-1-git-send-email-xiaohui.xin@intel.com> <1280442682.9058.15.camel@localhost.localdomain> <4C525CD2.5080604@redhat.com> Content-Type: text/plain; charset="UTF-8" Date: Fri, 30 Jul 2010 08:46:11 -0700 Message-ID: <1280504771.9058.25.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 (2.28.3-1.fc12) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Avi, On Fri, 2010-07-30 at 08:02 +0300, Avi Kivity wrote: > get_user_pages() is indeed slow. But what about > get_user_pages_fast()? > > Note that when the page is first touched, get_user_pages_fast() falls > back to get_user_pages(), so the latency needs to be measured after > quite a bit of warm-up. Yes, I used get_user_pages_fast, however if falled back to get_user_pages() when the apps doesn't allocate buffer on the same page. If I run a single ping, the RTT is extremely high, but when running multiple pings, the RTT time reduce significantly, but still it is not as fast as copy from my initial test. I am thinking that we might need to pre-pin memory pool. Shirley