From 59a32e2ce5eb809967cac4e718bc527beca83c59 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 23 Mar 2012 15:02:53 -0700 Subject: [PATCH] proc: speed up /proc/stat handling 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: Paul Turner Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Alexey Dobriyan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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 121f77cfef76..ac446114cd48 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; -- GitLab