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 42090C77B73 for ; Wed, 24 May 2023 07:35:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239954AbjEXHfW (ORCPT ); Wed, 24 May 2023 03:35:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37450 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239948AbjEXHfT (ORCPT ); Wed, 24 May 2023 03:35:19 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5D1C79E for ; Wed, 24 May 2023 00:35:15 -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=qkbTHa74RqVx5scyvuURKZ3IXXkvsRG06ONrBK7Q0vM=; b=SEeenSyO+zoxIqiysPU5pxE140 yqb6r8HRIiROJ5lXrscO8mPffvWto3MvioiJsWQNKw8clYMCI6df/HodWIi+pgAA/9A3MWG/u/Kg0 s0zBJq8aCcQzV8yiNqudF8vv5v4CL4t5beE7+oisxi29rxJ8kB018XL1l7Xne7RDdP8jNxNXjutZt agebM0jy+xlvBc7+bB87it1Y2/nGdhd2Cc3UuOeOygQto62TiHaga56su+y8Ww4YPnbNted1aIBaT lGKFWS7x7Fc1PsUlgDnefjAUxmWljRsULUBn+47ZY9ugj/gLC1ixkb/H0+a7so3/DFtNj4b25QqhX fScvd7aw==; 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 1q1j1O-00AyiB-Jv; Wed, 24 May 2023 07:34:58 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 5D48C300322; Wed, 24 May 2023 09:34:56 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 41EEE212FC822; Wed, 24 May 2023 09:34:56 +0200 (CEST) Date: Wed, 24 May 2023 09:34:56 +0200 From: Peter Zijlstra To: Vincent Guittot Cc: Tejun Heo , jiangshanlai@gmail.com, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, joshdon@google.com, brho@google.com, briannorris@chromium.org, nhuck@google.com, agk@redhat.com, snitzer@kernel.org, void@manifault.com, gautham.shenoy@amd.com Subject: Re: [PATCHSET v1 wq/for-6.5] workqueue: Improve unbound workqueue execution locality Message-ID: <20230524073456.GO83892@hirez.programming.kicks-ass.net> References: <20230519001709.2563-1-tj@kernel.org> <20230523111818.GH4253@hirez.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 Tue, May 23, 2023 at 06:12:45PM +0200, Vincent Guittot wrote: > Another possibility to investigate would be that each wakeup of a > worker is mostly unrelated to the previous one and it cares only > waker. so we should use -1 for the prev_cpu Tejun is actually overriding p->wake_cpu in this series to target a specific LLC -- with the explicit purpose to keep the workers near enough. But the problem is that with lots of short tasks we then overload the LLC and are not running long enough for the idle load-balancer to spread things, leading to idle time. And that is specific to this lots of little LLC topologies.