From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753524Ab1I1H3K (ORCPT ); Wed, 28 Sep 2011 03:29:10 -0400 Received: from beauty.rexursive.com ([150.101.121.179]:36207 "EHLO beauty.rexursive.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751785Ab1I1H3I (ORCPT ); Wed, 28 Sep 2011 03:29:08 -0400 Subject: Re: [PATCH v5]: Improve performance of LZO hibernation From: Bojan Smojver To: Pekka Enberg Cc: linux-kernel@vger.kernel.org, "Rafael J. Wysocki" Date: Wed, 28 Sep 2011 17:29:07 +1000 In-Reply-To: References: <1317183650.2067.10.camel@shrek.rexursive.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.0.3 (3.0.3-1.fc15) Content-Transfer-Encoding: 7bit Message-ID: <1317194947.1998.18.camel@shrek.rexursive.com> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2011-09-28 at 10:22 +0300, Pekka Enberg wrote: > > + while(1) { > > + wait_event(d->go, atomic_read(&d->ready) || > > + kthread_should_stop()); > > + if (kthread_should_stop()) > > + break; > > So... what happens to the hibernation process when 'kthread_should_stop()' > returns true? The compression/decompression threads stop by breaking out of the loop. At least they should, right? Did I misread some docs here? PS. I'm not really a kernel programmer, so I'm kinda stumbling my way through all this. > > + nthr = num_online_cpus() - 1; > > + nthr = nthr > LZO_THREADS ? LZO_THREADS : (nthr < 1 ? 1 : nthr); > > That's probably one of the most unreadable uses of the ternary > operator I've ever seen! Sorry about that. I can simplify. > What's going on here anyway? Why "num_online_cpus() - 1"? What's wrong with > > nr_threads = num_online_cpus(); > if (nr_threads > LZO_THREADS) > nr_threads = LZO_THREADS; We want to keep at least one CPU free for that I/O and for pulling the other threads into sync when they are done (that is if we have more than one), right? > [ And yes, please use less cryptic variable names. ] OK, been pulled over for that before. Will fix. > Overall, I really like your patch! Thanks, hopefully it doesn't blow up too many file systems :-) -- Bojan