From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastien Buisson Subject: [PATCH] Allow increasing the buffer-head per-CPU LRU size Date: Fri, 27 Jun 2014 14:25:24 +0200 Message-ID: <53AD62B4.1010203@bull.net> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit To: , , Return-path: Received: from odin2.bull.net ([129.184.85.11]:50773 "EHLO odin2.bull.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752779AbaF0MZ0 (ORCPT ); Fri, 27 Jun 2014 08:25:26 -0400 Sender: linux-fsdevel-owner@vger.kernel.org List-ID: 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..afea808 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 "buffer head per-CPU LRU size" + range 8 64 + default "16" + help + This sets the per-CPU LRU size for buffer heads in memory. + More complex filesystems may be modiyfing multiple blocks + within a single transaction, so keeping the buffer heads in + CPU-local cache speeds up modifations 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