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 X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A817EC388F2 for ; Mon, 2 Nov 2020 14:18:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 54D212068E for ; Mon, 2 Nov 2020 14:18:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="W+zuVyln" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726197AbgKBOSL (ORCPT ); Mon, 2 Nov 2020 09:18:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46666 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725817AbgKBOQh (ORCPT ); Mon, 2 Nov 2020 09:16:37 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 377BDC0617A6 for ; Mon, 2 Nov 2020 06:16:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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=UD/OkCMd1FoU3EgKfSru1bYvN7JBNcEWgNchKvRXMSM=; b=W+zuVylnGl4SAsNM85FlVkuMLf iBAwv+Ow46wK0I0qTRTpgV4fXAxHAJlvx8bR6cX2taNKpNPlT+9kOLWDmQEy+L/wyDSAXc8wF38gF u0HyEM9cwy/o8uDy09QdzPHgRS2BAInsivfWoryyGEHYg+tKYRuzcxJyVwdeWwbqLfDYgidYg+OoL v1xQHlMtgujMNSrk7N9f/EfKFX05/rXu97E8PAovxV63g3SfA4lwN9dDVQqdEMmhb8OFtWAcj/FOB UOtY+uY5OX6YH82efGC5rnB5949UAyH0kWoJfKQL4mmwFuWUvcv1RabS6GnsowFQGxZ4IFOk5goU7 DFoRgHDw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kZadJ-00083a-2u; Mon, 02 Nov 2020 14:16:29 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id DEAFE3011E6; Mon, 2 Nov 2020 15:16:25 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 929D72BEF6301; Mon, 2 Nov 2020 15:16:25 +0100 (CET) Date: Mon, 2 Nov 2020 15:16:25 +0100 From: Peter Zijlstra To: Andi Kleen Cc: Jiri Olsa , mingo@kernel.org, acme@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, namhyung@kernel.org, linux-kernel@vger.kernel.org, eranian@google.com Subject: Re: [PATCH v2 0/4] perf: Fix perf_event_attr::exclusive rotation Message-ID: <20201102141625.GX2594@hirez.programming.kicks-ass.net> References: <20201029162719.519685265@infradead.org> <20201031234418.GE3380099@krava> <20201102035238.GI466880@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201102035238.GI466880@tassilo.jf.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Nov 01, 2020 at 07:52:38PM -0800, Andi Kleen wrote: > The main motivation is actually that the "multiple groups" algorithm > in perf doesn't work all that great: it has quite a few cases where it > starves groups or makes the wrong decisions. That is because it is very > difficult (likely NP complete) problem and the kernel takes a lot > of short cuts to avoid spending too much time on it. The event scheduling should be starvation free, except in the presence of pinned events. If you can show starvation without pinned events, it's a bug. It will also always do equal or better than exclusive mode wrt PMU utilization. Again, if it doesn't it's a bug. Please provide concrete examples for these two cases, or stop spreading FUD like this.