From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.13]) (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 4D91B3A1A1 for ; Mon, 22 Jan 2024 10:13:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.13 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705918406; cv=none; b=ML2jWuBY8+TlBnmfPJ5EEhPEOddBs2z86nCg7lBD2g0CdOVZIYJCPb4/y9qqhQVIxP8yLGPiZWKiSadzaFtywWKt22PfBch5Yusa3T0oD1CPSoIXcZDGySyAWo7AR5HD2T2BueMne8valEHSdbWiS9xvAOyxIpJ31A0Mj7nB6R0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705918406; c=relaxed/simple; bh=9P+U30bR7kdblG2AxhM1pHhlDtODws/tQ2P3oU5CvNA=; h=From:To:References:Date:In-Reply-To:Message-ID:MIME-Version: Content-Type; b=Ah7N0FnXw2+a/nD1EFJSRdhXDWBOPUYgtlh5Tuk996uxHgk24mDFFNM0OvQlp2ntFCOaEZfwP0Hq/K7ZMiNrsGMiBzaczQwjpFdKYTSD5D3JmU/jMrl+Gg8nA+wW+IFFYqw2CTrx67buWwYMqWIaBeMvAHnxSkQRSo1MUfvuHGc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=JIb6DBm3; arc=none smtp.client-ip=192.198.163.13 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="JIb6DBm3" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1705918405; x=1737454405; h=from:to:references:date:in-reply-to:message-id: mime-version; bh=9P+U30bR7kdblG2AxhM1pHhlDtODws/tQ2P3oU5CvNA=; b=JIb6DBm3r0MNvAc78cYzMpuzqtB+nAixCNR1MUyxwiAvI05gV8HKAyRt ci8sYQTHgrnc+2D4FiH56Snw7ciRWmZnkDk5refiLCBO6Nk9Ntjsq28wm JvQiNfnZ5YX05cy15yVGXTJa5ZU0lGKprQUSkOXqGTBBEBCqrlsEz0jAY 6aoH1UsdnlLhPVp9zHMbwzwv3rhfh64YVlrx1oTUxDLMGuM4aE2FIeogS VMKmx37SPltLNVch5vHOD2CImggbQWWAYXpVxfzRS9JRDu89tkbL315OK NkpkeWet3bgpHmQToZEl5zB3uXyht3rHQXN6x4RK72/a5ojqjQ3eW//Ir w==; X-IronPort-AV: E=McAfee;i="6600,9927,10960"; a="61405" X-IronPort-AV: E=Sophos;i="6.05,211,1701158400"; d="scan'208";a="61405" Received: from orviesa005.jf.intel.com ([10.64.159.145]) by fmvoesa107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Jan 2024 02:13:24 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.05,211,1701158400"; d="scan'208";a="1164931" Received: from tassilo.jf.intel.com (HELO tassilo.localdomain) ([10.54.38.190]) by orviesa005.jf.intel.com with ESMTP; 22 Jan 2024 02:13:24 -0800 Received: by tassilo.localdomain (Postfix, from userid 1000) id 9563F301BE1; Mon, 22 Jan 2024 02:13:23 -0800 (PST) From: Andi Kleen To: linux-xfs@vger.kernel.org, david@fromorbit.com, linux-mm@kvack.org References: <20240118222216.4131379-1-david@fromorbit.com> Date: Mon, 22 Jan 2024 02:13:23 -0800 In-Reply-To: <20240118222216.4131379-1-david@fromorbit.com> (Dave Chinner's message of "Fri, 19 Jan 2024 09:19:38 +1100") Message-ID: <87zfwxk75o.fsf@linux.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Dave Chinner writes: > Thoughts, comments, etc? The interesting part is if it will cause additional tail latencies allocating under fragmentation with direct reclaim, compaction etc. being triggered before it falls back to the base page path. In fact it is highly likely it will, the question is just how bad it is. Unfortunately benchmarking for that isn't that easy, it needs artificial memory fragmentation and then some high stress workload, and then instrumenting the transactions for individual latencies. I would in any case add a tunable for it in case people run into this. Tail latencies are a common concern on many IO workloads. -Andi