From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D3DA518FA2D; Wed, 10 Jul 2024 11:59:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720612781; cv=none; b=rrFSA/wJe2GkUuCU36r003T3ahpMV80R1hnekALwrnnTC82o1MKnNkQKX2zdYYw4xgW0QeSuRXjHssC6bDfhnnSvRKls6StwP12iW0C9FbzE2OnAw9NpbRlxCETDSmRw+Xhn5TY++IWFetZnnPdneJ+B1BoErOmEbQL9wWAbopE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720612781; c=relaxed/simple; bh=WVKnzcm/NtngNFWbiRKfyh9T0w1WwExdL6PPrH+BjwA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ntpkYM4QWVdqoFV8Cjb+oAQFJmWkAV3no+eNg7j0ce99jYHg8CoM7yFUz77Mz3u+BkA28iQqxW7z3VmPmTqgIt67W7oIp3ZlihcAc1HbX5mRKDiw82AUPtjhc1+4B6I/n5RpquDDVBqz9qHnc380a3YVxHbq09NLTqZIIPD2zpg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=aORXPyqf; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="aORXPyqf" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; 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=UpzBiezjxdVclFwDJVsEbu3tBtzGfTOZYkXqYM2ZIrk=; b=aORXPyqfJTFEMY5N1DIcQ4CsCc x42+97zTngIUyKXXaWMwhyXuPAY9IWMegb4XtN8bl0yN88JGnbr2dO3/RpKSoOF/F5/gaL5lwNtSR vNEyWQNFigtL4DtBr1b8XLHNMXnrd53SEk5vuEZYU3GeTqtjT9ACk+vd+TfzyxnNGJKEga8qYyTLU +0U9tH3mpi1GlUlUzxnmyBlvA4haljBdgn4job9jhUUlcBaO5B/rVgIj4tvDxvLD+LYo/lFtmCoT4 x/l49QJwcYZN7uSDgJ95CdlhCNm95q/9qiU2Yn9Q2sXgAehQAeGD/RgKU94CyJCz0rHESPktYPxGA RiZnapXQ==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.97.1 #2 (Red Hat Linux)) id 1sRVyv-00000000tru-2PDm; Wed, 10 Jul 2024 11:59:33 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 16CF4300694; Wed, 10 Jul 2024 13:59:33 +0200 (CEST) Date: Wed, 10 Jul 2024 13:59:32 +0200 From: Peter Zijlstra To: kernel test robot Cc: Tejun Heo , oe-lkp@lists.linux.dev, lkp@intel.com, linux-kernel@vger.kernel.org, x86@kernel.org, ying.huang@intel.com, feng.tang@intel.com, fengwei.yin@intel.com, aubrey.li@linux.intel.com, yu.c.chen@intel.com Subject: Re: [tip:sched/core] [sched/fair] d329605287: stress-ng.resched.ops_per_sec -24.0% regression Message-ID: <20240710115932.GZ27299@noisy.programming.kicks-ass.net> References: <202407101139.6e513af5-oliver.sang@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202407101139.6e513af5-oliver.sang@intel.com> On Wed, Jul 10, 2024 at 12:51:44PM +0800, kernel test robot wrote: > > > Hello, > > kernel test robot noticed a -24.0% regression of stress-ng.resched.ops_per_sec on: > > > commit: d329605287020c3d1c3b0dadc63d8208e7251382 ("sched/fair: set_load_weight() must also call reweight_task() for SCHED_IDLE tasks") > https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git sched/core > > testcase: stress-ng > test machine: 64 threads 2 sockets Intel(R) Xeon(R) Gold 6346 CPU @ 3.10GHz (Ice Lake) with 256G memory > parameters: > > nr_threads: 100% > testtime: 60s > test: resched > cpufreq_governor: performance Well.... if I read the test source correctly, this seems to test how fast it can call sched_setscheduler(), rather than test how fast we can schedule. And that patch mentioned above makes setting SCHED_IDLE more expensve -- as expensive as SCHED_OTHER and SCHED_BATCH. I'm thinking this test is rather stupid and doesn't actually measure anything useful, I don't think I consider sched_setscheduler() a fast path by any means. Su yeah, *shrug*.