From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B952EE7C4E7 for ; Wed, 4 Oct 2023 17:48:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243441AbjJDRsV (ORCPT ); Wed, 4 Oct 2023 13:48:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39030 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233397AbjJDRsU (ORCPT ); Wed, 4 Oct 2023 13:48:20 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DA6409E for ; Wed, 4 Oct 2023 10:48:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=cCyNQY2PqRUUwPVEhQWWTvU6sVIE17n3grQQ+eFVYPo=; b=GNG8f37hv9dXl/xj4GQO6Ms+X9 7hZxFURq6Hyelp5HeRptfl2Iy8DnVMgma7qSR1sAoxnYTuZjhFBFunOP5nrM6ktQHq+cqkgmvLzxg JKK7jkssuLx03mz3uxYwMvFmuDMfaX0H6gdejJlAbIyG1dbZq2TQREWeMK+BP99/KxdncWqeZTA3l HUQ84Hy8VHUItgcC6A/z8xZ9aGynGZV3eMbHBT85LBOQRboBQqD+MdlOZzm76gh+teukAHlImKuyW bpQ8wAXYjzFZH2/JNdi3Jwo2yuvvL2vx8cMfzFbcTjAkYV5ujXs+KbnpocGu8kF1CXQ9UTO6lXzMf lK1qQ0UQ==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1qo5yb-004f4g-P6; Wed, 04 Oct 2023 17:48:01 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 71A76300392; Wed, 4 Oct 2023 19:48:01 +0200 (CEST) Date: Wed, 4 Oct 2023 19:48:01 +0200 From: Peter Zijlstra To: Julia Lawall Cc: Ingo Molnar , Vincent Guittot , Dietmar Eggemann , Mel Gorman , linux-kernel@vger.kernel.org Subject: Re: EEVDF and NUMA balancing Message-ID: <20231004174801.GE19999@noisy.programming.kicks-ass.net> References: <20231003215159.GJ1539@noisy.programming.kicks-ass.net> <20231004120544.GA6307@noisy.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 04, 2023 at 06:24:39PM +0200, Julia Lawall wrote: > > > On Wed, 4 Oct 2023, Peter Zijlstra wrote: > > > On Wed, Oct 04, 2023 at 02:01:26PM +0200, Julia Lawall wrote: > > > > > > > > > On Tue, 3 Oct 2023, Peter Zijlstra wrote: > > > > > > > On Tue, Oct 03, 2023 at 10:25:08PM +0200, Julia Lawall wrote: > > > > > Is it expected that the commit e8f331bcc270 should have an impact on the > > > > > frequency of NUMA balancing? > > > > > > > > Definitely not expected. The only effect of that commit was supposed to > > > > be the runqueue order of tasks. I'll go stare at it in the morning -- > > > > definitely too late for critical thinking atm. > > > > > > Maybe it's just randomly making a bad situation worse rather than directly > > > introduing a problem. There is a high standard deviatind in the > > > performance. Here are some results with hyperfine. The general trends > > > are reproducible. > > > > OK,. I'm still busy trying to bring a 4 socket machine up-to-date... > > gawd I hate the boot times on those machines :/ > > > > But yeah, I was thinking similar things, I really can't spot an obvious > > fail in that commit. > > > > I'll go have a poke once the darn machine is willing to submit :-) > > I tried a two-socket machine, but in 50 runs the problem doesn't show up. I've had to re-install the 4 socket thing -- lost the day to this trainwreck :/ Because obvoiusly the BMC needs Java and that all don't work anymore -- so I had to go sit next to the jet-engine thing with a keyboard and monitor. I'll go build the benchmark thing tomorrow, if I can figure out how that works, this NAS stuff looked 'special'. Nothing simple like ./configure; make -j$lots :/ > The commit e8f331bcc270 starts with > > - if (sched_feat(PLACE_LAG) && cfs_rq->nr_running > 1) { > + if (sched_feat(PLACE_LAG) && cfs_rq->nr_running) { > > This seemed like a big change - cfs_rq->nr_running > 1 should be rarely > true in ua, while cfs_rq->nr_running should always be true. Adding back > the > 1 and simply replacing the test by 0 both had no effect, though. Yeah, this is because I flip the order of place_entity() and nr_running++ around later in the patch. Previously it would increment before place, now it does place before increment.