From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754347Ab3FKXWe (ORCPT ); Tue, 11 Jun 2013 19:22:34 -0400 Received: from mga09.intel.com ([134.134.136.24]:13532 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752657Ab3FKXWd (ORCPT ); Tue, 11 Jun 2013 19:22:33 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.87,848,1363158000"; d="scan'208";a="351967431" Message-ID: <51B7B128.60909@intel.com> Date: Tue, 11 Jun 2013 16:22:16 -0700 From: Dave Hansen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130510 Thunderbird/17.0.6 MIME-Version: 1.0 To: linux-ext4@vger.kernel.org, LKML , "Theodore Ts'o" , Jan kara Subject: ext4 extent status tree LRU locking Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I've got a test case which I intended to use to stress the VM a bit. It fills memory up with page cache a couple of times. It essentially runs 30 or so cp's in parallel. 98% of my CPU is system time, and 96% of _that_ is being spent on the spinlock in ext4_es_lru_add(). I think the LRU list head and its lock end up being *REALLY* hot cachelines and are *the* bottleneck on this test. Note that this is _before_ we go in to reclaim and actually start calling in to the shrinker. There is zero memory pressure in this test. I'm not sure the benefits of having a proper in-order LRU during reclaim outweigh such a drastic downside for the common case. Any thoughts?