From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 20 May 2002 09:34:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 20 May 2002 09:34:53 -0400 Received: from samba.sourceforge.net ([198.186.203.85]:48063 "HELO lists.samba.org") by vger.kernel.org with SMTP id ; Mon, 20 May 2002 09:34:53 -0400 Date: Mon, 20 May 2002 23:31:05 +1000 From: Anton Blanchard To: Dipankar Sarma Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Alan Cox , Dave Miller Subject: Re: [RFC][PATCH] TIMER_BH-less smptimers Message-ID: <20020520133105.GC14488@krispykreme> In-Reply-To: <20020516185448.A8069@in.ibm.com> <20020520085500.GB14488@krispykreme> <20020520155958.F6270@in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.28i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi Dipankar, > The tasklet code also needs fixing. It is a miracle that the kernel > booted when I tested that code. Here is a fixed diff. :) I was surprised it worked with the missing spin_unlock too. Im testing the fixed diff now, so far it looks good. > I am curious about performance of smptimers. It seems that > webserver benchmark performance worsens with smptimers (Ingo version) > contrary to our expectations. Do you see this ? If so, could this > happen because - > > 1) Bouncing around of global_bh_lock cacheline by more cpus compared > to earlier timer implemenation ? > 2) All per-cpu timers invoked from timer_bh running in one cpu ? > > Do you see any other side-effects of smptimers ? We used to see bad behaviour. It turned out to be the per cpu timer interrupt firing at exactly the same time on all cpus. One cpu would successfully spin_trylock and the others would fail and postpone the work. We now evenly space the per cpu interrupts. Does intel do the same? > Also, did my PPC changes for smptimers work or you had to fix it ? I tested ppc64 and it worked fine. Anton