From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Xu Subject: reduce networking latency Date: Tue, 10 Jun 2014 11:29:39 -0400 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 To: kvm Return-path: Received: from mail-qg0-f52.google.com ([209.85.192.52]:38762 "EHLO mail-qg0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750758AbaFJP3k (ORCPT ); Tue, 10 Jun 2014 11:29:40 -0400 Received: by mail-qg0-f52.google.com with SMTP id a108so10720116qge.11 for ; Tue, 10 Jun 2014 08:29:39 -0700 (PDT) Sender: kvm-owner@vger.kernel.org List-ID: Hi All, I found this interesting project from KVM TODO website: allow handling short packets from softirq or VCPU context Plan: We are going through the scheduler 3 times (could be up to 5 if softirqd is involved) Consider RX: host irq -> io thread -> VCPU thread -> guest irq -> guest thread. This adds a lot of latency. We can cut it by some 1.5x if we do a bit of work either in the VCPU or softirq context. Testing: netperf TCP RR - should be improved drastically netperf TCP STREAM guest to host - no regression Developer: MST I am also tuning the vCPU scheduling of KVM. If someone would like to say some details about the work either in the vCPU or softirq context, I will be very appreciated. BTW, how to get the evaluation results that the shortcut can improve the performance by up to 1.5X? Thanks a lot! Regards, Cong