From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (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 02AB73502A3 for ; Mon, 20 Jul 2026 07:58:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.11.211 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784534294; cv=none; b=OhF/fOdGgCLwzpJqkO3ZXk+2hfiwua2gVZkxWhbXh22rnyxgi+YHH1Q6RqSiyhq+KwzPhSV1juJTtyR+bIwxJHwrSNbHgGt/+iGdmooOw8J4ZeY4EUhtcRtaBqawYirgVhpurZ9VAYDSoGmd7TvfpVICwWiD6pP7D09eqA1D5uw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784534294; c=relaxed/simple; bh=z2pV5+m7oywp5F57tdzfLtRpSn1K0sQzxY2FXhn1+5s=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tLwo9x/p5BcHTseXI7k6vwtOQFLzi0PP6IBtNJK5We9QmWfBfl2KPgVNyn6ms+8xWmx1UT3Omt1tLCma6qCVobhbFBSC1jOiLNPvgWbXuPSgNz5gZZivM1Xy2KiAYWwPF99Wv93tDOKJ6U092lOm9GHoL/gfPKOKAuO/dbh5bOk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.client-ip=213.95.11.211 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lst.de Received: by verein.lst.de (Postfix, from userid 2407) id 1D8E968BEB; Mon, 20 Jul 2026 09:58:02 +0200 (CEST) Date: Mon, 20 Jul 2026 09:58:01 +0200 From: Christoph Hellwig To: Oliver Sang Cc: Christoph Hellwig , oe-lkp@lists.linux.dev, lkp@intel.com, linux-kernel@vger.kernel.org, Carlos Maiolino , Carlos Maiolino , "Darrick J. Wong" , linux-xfs@vger.kernel.org Subject: Re: [linus:master] [xfs] 9b64ca202f: fxmark.ssd_xfs_DRBH_4_bufferedio.works/sec 24.1% regression Message-ID: <20260720075801.GA18087@lst.de> References: <202607161601.867c143e-lkp@intel.com> <20260717064807.GA23992@lst.de> Precedence: bulk X-Mailing-List: oe-lkp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) On Sun, Jul 19, 2026 at 04:16:14PM +0800, Oliver Sang wrote: > hi, Christoph Hellwig, > > On Fri, Jul 17, 2026 at 08:48:07AM +0200, Christoph Hellwig wrote: > > On Thu, Jul 16, 2026 at 09:13:19PM +0800, kernel test robot wrote: > > > > > > > > > Hello, > > > > > > kernel test robot noticed a 24.1% regression of fxmark.ssd_xfs_DRBH_4_bufferedio.works/sec on: > > > > > > > This looks really odd. While the patch adds a bit more computation, > > that is very cheap shifting and masking. > > in order to avoid the false positive, we rebuilt the kernel and rerun tests > on both 9b64ca202f and its parent. though the data has some differences with > last time, the regression trend is still similar - 21.8% regression this time. > > > > So the only theory I have here > > is that this somehow affects the inode data layout. Can you re-run this > > with the patch below applied on top of commit > > 9b64ca202f364a6bf8e19bdd20953bc2d776c67f ? > > yeah, but applying your patch upon 9b64ca202f, we saw the regression recovered. > > from average data, it now becomes even little better than the parent of > 9b64ca202f, i.e. caffb4252c, but since the data is not very stable - 4% stddev > for caffb4252c and 6% stddev for bd79e961ea, we cannot call +3.1% a valid > improvement according to our bot's rules. Already, so this must be something about cache line sharing. I'll try to get hold of a big enough test box to see if I can reproduce this, in the worst case we'll have to just add back the padding for now.