From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753782Ab0CJTfU (ORCPT ); Wed, 10 Mar 2010 14:35:20 -0500 Received: from casper.infradead.org ([85.118.1.10]:34589 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753346Ab0CJTfR convert rfc822-to-8bit (ORCPT ); Wed, 10 Mar 2010 14:35:17 -0500 Subject: Re: [RFC PATCH] perf: Store relevant events in a hlist From: Peter Zijlstra To: Frederic Weisbecker Cc: LKML , Ingo Molnar , Paul Mackerras , Steven Rostedt , Masami Hiramatsu , Jason Baron , Arnaldo Carvalho de Melo In-Reply-To: <20100308183545.GA5038@nowhere> References: <1267772426-5944-1-git-send-regression-fweisbec@gmail.com> <1267772426-5944-2-git-send-regression-fweisbec@gmail.com> <1267781969.16716.55.camel@laptop> <20100308183545.GA5038@nowhere> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Wed, 10 Mar 2010 20:34:52 +0100 Message-ID: <1268249692.5279.138.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2010-03-08 at 19:35 +0100, Frederic Weisbecker wrote: > On Fri, Mar 05, 2010 at 10:39:29AM +0100, Peter Zijlstra wrote: > > On Fri, 2010-03-05 at 08:00 +0100, Frederic Weisbecker wrote: > > > Each time a trace event triggers, we walk through the entire > > > list of events from the active contexts to find the perf events > > > that match the current one. > > > > > > This is wasteful. To solve this, we maintain a per cpu list of > > > the active perf events for each running trace events and we > > > directly commit to these. > > > > Right, so this seems a little trace specific. I once thought about using > > a hash table to do this for all software events. It also keeps it all > > nicely inside perf_event.[ch]. > > > What do you think about this version? > It builds but crashes on runtime and doesn't handle > cpu hotplug yet. Before spending more time in debugging/fixing, > I'd like to know your opinion about the general architecture. > > Thanks. > > --- > From c389b296a87bd38cfd28da3124508eb1e5a5d553 Mon Sep 17 00:00:00 2001 > From: Frederic Weisbecker > Date: Mon, 8 Mar 2010 19:04:02 +0100 > Subject: [PATCH] perf: Store relevant events in a hlist > > When a software/tracepoint event triggers, we walk through the > entire current cpu and task context's events lists to retrieve > those that are concerned. > > This is wasteful. This patch proposes a hashlist to walk through > the relevant events only. The hash is calculated using the id of > the event (could be further optimized using the type of the event > too). Each hash map a list of distinct type:id that match the hash. > To these type:id nodes, we affect a list of the active events > matching the type:id. > > ----------------------- > Hash 1 | Hash 2 | .... > ---------------------- > | > swevent type:id node > | | > | ------- event 1 ---- event 2 ---- .... > | > swevent type:id node > | > --------[...] > > The hashlist is per cpu (attached to perf_cpu_context) and the > events in the lists gather those that are active in the cpu and > task context. No more per events checks are needed to guess if > the events are "counting" or "matching". I'm not quite sure why you need the node thing, you already have a hash-bucket to iterate, simply stick all events into the one bucket and walk through it with a filter and process all events that match. As to all those for_each_online_cpu() thingies, it might make sense to also have a global hash-table for events active on all cpus,... hmm was that the reason for the node thing, one event cannot be in multiple buckets?