From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754319Ab2AYAB3 (ORCPT ); Tue, 24 Jan 2012 19:01:29 -0500 Received: from mail-ww0-f44.google.com ([74.125.82.44]:39494 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754049Ab2AYAB2 (ORCPT ); Tue, 24 Jan 2012 19:01:28 -0500 Message-ID: <1327449683.14373.12.camel@edumazet-laptop> Subject: [PATCH v2] proc: speedup /proc/stat handling From: Eric Dumazet To: Andrew Morton Cc: KAMEZAWA Hiroyuki , Glauber Costa , Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org, Russell King - ARM Linux , Paul Tuner Date: Wed, 25 Jan 2012 01:01:23 +0100 In-Reply-To: <1327075164.12389.31.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> References: <1327075164.12389.31.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.2- Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On a typical 16 cpus machine, "cat /proc/stat" gives more than 4096 bytes, and is slow : # strace -T -o /tmp/STRACE cat /proc/stat | wc -c 5826 # grep "cpu " /tmp/STRACE read(0, "cpu 1949310 19 2144714 12117253"..., 32768) = 5826 <0.001504> Thats partly because show_stat() must be called twice since initial buffer size is too small (4096 bytes for less than 32 possible cpus) Fix this by : 1) Taking into account nr_irqs in the initial buffer sizing. 2) Using ksize() to allow better filling of initial buffer. Signed-off-by: Eric Dumazet Cc: Glauber Costa Cc: Russell King - ARM Linux Cc: KAMEZAWA Hiroyuki Cc: Andrew Morton Cc: Paul Tuner Cc: Peter Zijlstra Cc: Ingo Molnar --- V2: No change on "intr" line for compatibility sake. fs/proc/stat.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/proc/stat.c b/fs/proc/stat.c index 121f77c..ac44611 100644 --- a/fs/proc/stat.c +++ b/fs/proc/stat.c @@ -157,11 +157,14 @@ static int show_stat(struct seq_file *p, void *v) static int stat_open(struct inode *inode, struct file *file) { - unsigned size = 4096 * (1 + num_possible_cpus() / 32); + unsigned size = 1024 + 128 * num_possible_cpus(); char *buf; struct seq_file *m; int res; + /* minimum size to display an interrupt count : 2 bytes */ + size += 2 * nr_irqs; + /* don't ask for more than the kmalloc() max size */ if (size > KMALLOC_MAX_SIZE) size = KMALLOC_MAX_SIZE; @@ -173,7 +176,7 @@ static int stat_open(struct inode *inode, struct file *file) if (!res) { m = file->private_data; m->buf = buf; - m->size = size; + m->size = ksize(buf); } else kfree(buf); return res;