From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Abeni Subject: Re: [RFC PATCH 0/2] net: threadable napi poll loop Date: Mon, 16 May 2016 15:10:32 +0200 Message-ID: <1463404232.4921.26.camel@redhat.com> References: <1462890590.23934.68.camel@edumazet-glaptop3.roam.corp.google.com> <90f3db8c-c30c-b204-576a-454939ac93ce@stressinduktion.org> <94f323a9-515e-4d75-cac8-ef0214f0499e@stressinduktion.org> <1462920697.23934.113.camel@edumazet-glaptop3.roam.corp.google.com> <20160511065527.GD3193@twins.programming.kicks-ass.net> <1463003804.23934.154.camel@edumazet-glaptop3.roam.corp.google.com> <1463158203.11721.25.camel@redhat.com> <1463159940.11721.37.camel@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Eric Dumazet , Peter Zijlstra , Hannes Frederic Sowa , netdev , "David S. Miller" , Jiri Pirko , Daniel Borkmann , Alexei Starovoitov , Alexander Duyck , Tom Herbert , Ingo Molnar , Rik van Riel , LKML , "Paul E. McKenney" To: Eric Dumazet Return-path: Received: from mx1.redhat.com ([209.132.183.28]:53434 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753527AbcEPNKi (ORCPT ); Mon, 16 May 2016 09:10:38 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 2016-05-13 at 10:36 -0700, Eric Dumazet wrote: > On Fri, May 13, 2016 at 10:19 AM, Paolo Abeni wrote: > > > The difference is small, in the noise range: > > > > [with this patch applied] > > super_netperf 100 -H 192.168.122.1 -t UDP_STREAM -l 60 -- -m 1 > > 9.00 > > > > [adding the test into __local_bh_enable_ip(), too] > > super_netperf 100 -H 192.168.122.1 -t UDP_STREAM -l 60 -- -m 1 > > 9.14 > > > > but reproducible, in my experiments. > > I have similar data for different number of flows. > > > >> I believe I did this so that we factorize the logic in do_softirq() > >> and keep the code local to kernel/softirq.c > >> > >> Otherwise, netif_rx_ni() could also process softirq while ksoftirqd > >> was scheduled, > >> so I would have to 'export' the ksoftirqd_running(void) helper in an > >> include file. > > > > The idea could be to add the test in __local_bh_enable_ip(), maintaining > > the test also in do_softirq() (as currently done, i.e for > > local_softirq_pending()) > > > > Then I guess even the !in_interrupt() test we do is expensive and > could be avoided, > since do_softirq() is doing it again in the unlikely case it really is needed. > > @@ -162,7 +170,8 @@ void __local_bh_enable_ip(unsigned long ip, > unsigned int cnt) > */ > preempt_count_sub(cnt - 1); > > - if (unlikely(!in_interrupt() && local_softirq_pending())) { > + if (unlikely(local_softirq_pending()) && > + !ksoftirqd_running()) { > /* > * Run softirq if any pending. And do it in its own stack > * as we may be calling this deep in a task call stack already. I'm sorry for the not-so-prompt reply. I had to use a different H/W, so I had to re-run the tests with all the patch flavors to get comparable results. While I can confirm that adding the '!ksoftirqd_running()' condition improves the throughput a little, but in a reproducible way, removing the '!in_interrupt()' don't change the result measurably, in my environment. While running the test against a kernel with the above chunk applied I got a couple of: [ 702.791025] NOHZ: local_softirq_pending 08 Not seen with the other versions of this patch. Cheers, Paolo