From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 8A12B12880A; Thu, 4 Apr 2024 14:05:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712239540; cv=none; b=ObpFi7EaolaJ+4qK/gwBceZj5Oi2030hUtL4eEpY/DaA8TpKfO7/ymrP1KZ0l0cUMbHIdFeHwrGzKcGg85lXQLcdCJgbdpt9nTbBy8zkoFGASqDaQedLSnrUar3swk+eAhGNNRFPmh3r89mSWRL0MXKYZdANDgF9yUL/mzBIKdU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712239540; c=relaxed/simple; bh=U/MPpQggBCzuKAhHoUOfvrR+Z2ao2griNbbZUp9Y+FY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=J+X3DcFztgc2oAyGKt3BqDCxFmZTf2Yk+ayvPhbfDzvnMBmJE76T5j1EIoGZJfrbTio6WXrhVlk2uEbUFWG931hSGNdaCRp8J9CcoyM/GbF60dATVqaBkE4vb7Xedv/XNIl33PXEQM209JwHy3W0PuJZN7Hf1lfVrJGZlup13kA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qqz23xxk; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="qqz23xxk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B1F06C433F1; Thu, 4 Apr 2024 14:05:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1712239540; bh=U/MPpQggBCzuKAhHoUOfvrR+Z2ao2griNbbZUp9Y+FY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qqz23xxki1mIXnAn+WLvnaKU8EC8fa6V5d6k5Usmy77PxW7O+g/Val5wg3CcRaipW YKnVAkSAt+QkgRFy7T6+wLHcfe4VRNl0giMnZVtWuLT0+9vgk3x3IuFo0uSLILr2hF 38oCiSGmm9D9TiUbfdAiYMMze3u6lqZvXK+Mue1IKwOqdQkFRedSI0nnU1oifJA2QB iZGyfT6ZgaetNmvNRoUi/q9h/GVHhLkUoyRguasgV/EGkIx+OAH5A6obocOLzCsIBk QP0TJfX532W1p7z0iTei/pgnZdunysyNUKsQy6RnsEmkOnTbev8yM6/4+fAolbICX6 +HzJf7Dw7Gh3A== Date: Thu, 4 Apr 2024 16:05:37 +0200 From: Frederic Weisbecker To: Oliver Sang Cc: Anna-Maria Behnsen , oe-lkp@lists.linux.dev, lkp@intel.com, linux-kernel@vger.kernel.org, Thomas Gleixner , ying.huang@intel.com, feng.tang@intel.com, fengwei.yin@intel.com Subject: Re: [linus:master] [timers] 7ee9887703: stress-ng.uprobe.ops_per_sec -17.1% regression Message-ID: References: <202403271623.f0b40181-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=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Le Tue, Apr 02, 2024 at 09:46:29AM +0800, Oliver Sang a écrit : > hi, Frederic Weisbecker, > > On Tue, Apr 02, 2024 at 12:46:15AM +0200, Frederic Weisbecker wrote: > > Le Wed, Mar 27, 2024 at 04:39:17PM +0800, kernel test robot a écrit : > > > > > > > > > Hello, > > > > > > > > > we reported > > > "[tip:timers/core] [timers] 7ee9887703: netperf.Throughput_Mbps -1.2% regression" > > > in > > > https://lore.kernel.org/all/202403011511.24defbbd-oliver.sang@intel.com/ > > > > > > now we noticed this commit is in mainline and we captured further results. > > > > > > still include netperf results for complete. below details FYI. > > > > > > > > > kernel test robot noticed a -17.1% regression of stress-ng.uprobe.ops_per_sec > > > on: > > > > The good news is that I can reproduce. > > It has made me spot something already: > > > > https://lore.kernel.org/lkml/ZgsynV536q1L17IS@pavilion.home/T/#m28c37a943fdbcbadf0332cf9c32c350c74c403b0 > > > > But that's not enough to fix the regression. Investigation continues... > > Thanks a lot for information! if you want us test any patch, please let us know. The good news is that I can reproduce on two CPUs with just this: ./tmp-pkg/stress-ng/src/stress-ng/stress-ng --uprobe-ops 1 --uprobe 2 --timeout 5 --metrics-brief This reminds me I should try on a single CPU. Anyway but the big problem with stress-ng.uprobe is that it consists in triggering uprobes events and consuming /sys/kernel/tracing/trace_pipe This makes this testcase nearly impossible to analyse because I can't use any tracing: the traces are consumed by the testcase. That alone took me quite some time to figure out. Then I tried using perf event to do the tracing, as it relies on a different ring buffer. It works but traces generate ring buffer consumer wake up, which doesn't work as we are analysing code that depends on idle behaviour. Then I tried hacking stress-uprobe.c so that the consumed traces are recorded in a buffer that I writeback in the end. So I can add my own tracepoints in the flow. And it works but that again doesn't mix up well with tracing idle behaviour, similar to perf event: the fact that the testcase waits on /sys/kernel/tracing/trace_pipe produce wake ups from idle while a trace happen on idle. And that noise ruins the tracing. So I'm kind of running out of options for now :-/