Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752519AbaGGKcR (ORCPT ); Mon, 7 Jul 2014 06:32:17 -0400 Received: from odin2.bull.net ([129.184.85.11]:51907 "EHLO odin2.bull.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752433AbaGGKcO convert rfc822-to-8bit (ORCPT ); Mon, 7 Jul 2014 06:32:14 -0400 Message-ID: <53BA772C.6040506@bull.net> Date: Mon, 7 Jul 2014 12:32:12 +0200 From: Sebastien Buisson User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Andi Kleen CC: , , , Andrew Morton Subject: Re: [PATCH] Allow increasing the buffer-head per-CPU LRU size References: <53B667F9.90306@bull.net> <87y4w6sbp7.fsf@tassilo.jf.intel.com> In-Reply-To: <87y4w6sbp7.fsf@tassilo.jf.intel.com> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed X-Originating-IP: [10.192.1.123] Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Allow increasing the buffer-head per-CPU LRU size to allow efficient filesystem operations that access many blocks for each transaction. For example, creating a file in a large ext4 directory with quota enabled will accesses multiple buffer heads and will overflow the LRU at the default 8-block LRU size: * parent directory inode table block (ctime, nlinks for subdirs) * new inode bitmap * inode table block * 2 quota blocks * directory leaf block (not reused, but pollutes one cache entry) * 2 levels htree blocks (only one is reused, other pollutes cache) * 2 levels indirect/index blocks (only one is reused) The buffer-head per-CPU LRU size can be changed at config time, and its default value is raised to 16. Signed-off-by: Liang Zhen Signed-off-by: Andreas Dilger --- fs/Kconfig | 9 +++++++++ fs/buffer.c | 3 +-- 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/fs/Kconfig b/fs/Kconfig index c229f82..c08844c 100644 --- a/fs/Kconfig +++ b/fs/Kconfig @@ -268,4 +268,13 @@ endif # NETWORK_FILESYSTEMS source "fs/nls/Kconfig" source "fs/dlm/Kconfig" +config BH_LRU_SIZE + int + range 8 64 + default "16" + help + This sets the per-CPU LRU size for buffer heads in memory. + More complex filesystems may be modifying multiple blocks + within a single transaction, so keeping the buffer heads in + CPU-local cache speeds up modifications significantly. endmenu diff --git a/fs/buffer.c b/fs/buffer.c index 6024877..b83fa63 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -1255,8 +1255,7 @@ static struct buffer_head *__bread_slow(struct buffer_head *bh) * The LRUs themselves only need locking against invalidate_bh_lrus. We use * a local interrupt disable for that. */ - -#define BH_LRU_SIZE 8 +#define BH_LRU_SIZE CONFIG_BH_LRU_SIZE struct bh_lru { struct buffer_head *bhs[BH_LRU_SIZE]; -- 1.7.1 Le 06/07/2014 18:18, Andi Kleen a ?crit : > Sebastien Buisson writes: > >> Allow increasing the buffer-head per-CPU LRU size to allow efficient >> filesystem operations that access many blocks for each transaction. >> For example, creating a file in a large ext4 directory with quota >> enabled will accesses multiple buffer heads and will overflow the LRU >> at the default 8-block LRU size: > > I don't think that should be a user visible config. Most users wouldn't > know how to set it. And Linux already has far too many obscure > config options. > > Either make it set implicitely by the file system config. > Or just increase it unconditionally? > > -Andi > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/