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 BFD5CC4167B for ; Tue, 28 Nov 2023 14:02:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345329AbjK1OCn (ORCPT ); Tue, 28 Nov 2023 09:02:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39004 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344798AbjK1OCm (ORCPT ); Tue, 28 Nov 2023 09:02:42 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 67885B5; Tue, 28 Nov 2023 06:02:47 -0800 (PST) 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=Kbo+RHlcbyYyBRrrc3whU0Ok1x+trIWNBYTilsW1XuI=; b=WgmwKxv9CoPrJNaMGZ0b0cipit 1Dn8osLTNJw+PM7fRkJSHUnm8YFQE0eP566+F9DNMA31UbmW46JjaqhPe1c6A/qyBQ2/X3RYmO7nP bHA0iXTXxcNP7FYVb+NyAnLisit8kmbieBp+1G92bgHC59jJGDgGSVnuk+TcL/xPnmqAsl2Ul1Z6+ 9qJgpI0XzYQA/FCON0ITa20ltlhaiJDOcpBrVLRb46FzAhU/T5ZTX/W8YnDNWHbhUXBkW7b6w7GT9 ReXjB4GHT39ck5dC7am0UAwRNdrUFQvxFmmkMrHuI0vxK/29bBTRNETziKPoAZp5okldMW+Bh8K5K cpqdS1Vg==; 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 1r7yfT-00CPkR-Dz; Tue, 28 Nov 2023 14:02:27 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 8D8A83003F0; Tue, 28 Nov 2023 15:02:25 +0100 (CET) Date: Tue, 28 Nov 2023 15:02:25 +0100 From: Peter Zijlstra To: Bagas Sanjaya Cc: Linux Kernel Mailing List , Linux Regressions , Linux Power Management , "Rafael J. Wysocki" , Viresh Kumar , Ingo Molnar , Juri Lelli , Vincent Guittot , Ramses VdP , ricardo.neri-calderon@linux.intel.com Subject: Re: Fwd: Intel hybrid CPU scheduler always prefers E cores Message-ID: <20231128140225.GS8262@noisy.programming.kicks-ass.net> References: <01df8329-06d7-4fd1-9c7a-05296f33231e@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <01df8329-06d7-4fd1-9c7a-05296f33231e@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 28, 2023 at 08:22:27PM +0700, Bagas Sanjaya wrote: > Hi, > > I come across an interesting bug report on Bugzilla [1]. The reporter > wrote: Thanks for forwarding, what happend in bugzilla staysi in bugzilla etc.. Did you perchance Cc the reporter? > > I am running an intel alder lake system (Core i7-1260P), with a mix > > of P and E cores. > > > > Since Linux 6.6, and also on the current 6.7 RC, the scheduler seems > > to have a strong preference for the E cores, and single threaded > > workloads are consistently scheduled on one of the E cores. > > > > With Linux 6.4 and before, when I ran a single threaded CPU-bound > > process, it was scheduled on a P core. With 6.5, it seems that the > > choice of P or E seemed rather random. > > > > I tested these by running "stress" with different amounts of > > threads. With a single thread on Linux 6.6 and 6.7, I always have an > > E core at 100% and no load on the P cores. Starting from 3 threads I > > get some load on the P cores as well, but the E cores stay more > > heavily loaded. With "taskset" I can force a process to run on a P > > core, but clearly it's not very practical to have to do CPU > > scheduling manually. > > > > This severely affects single-threaded performance of my CPU since > > the E cores are considerably slower. Several of my workflows are now > > a lot slower due to them being single-threaded and heavily CPU-bound > > and being scheduled on E cores whereas they would run on P cores > > before. > > > > I am not sure what the exact desired behaviour is here, to balance > > power consumption and performance, but currently my P cores are > > barely used for single-threaded workloads. > > > > Is this intended behaviour or is this indeed a regression? Or is > > there perhaps any configuration that I should have done from my > > side? Is there any further info that I can provide to help you > > figure out what's going on? > > PM and scheduler people, is this a regression or works as intended? AFAIK that is supposed to be steered by the ITMT muck and I don't think we changed that. Ricardo? > > Thanks. > > [1]: https://bugzilla.kernel.org/show_bug.cgi?id=218195 > > -- > An old man doll... just what I always wanted! - Clara