From: Andrei Vagin <avagin@openvz.org>
To: linux-fsdevel@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
Andrei Vagin <avagin@openvz.org>,
Alexey Dobriyan <adobriyan@gmail.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Subject: [PATCH 2/2] procfs: optimize seq_pad() to speed up /proc/pid/maps
Date: Fri, 12 Jan 2018 10:58:12 -0800 [thread overview]
Message-ID: <20180112185812.7710-2-avagin@openvz.org> (raw)
In-Reply-To: <20180112185812.7710-1-avagin@openvz.org>
seq_printf() is slow and it can be replaced by memset() in this case.
== test.py
num = 0
with open("/proc/1/maps") as f:
while num < 10000 :
data = f.read()
f.seek(0, 0)
num = num + 1
==
== Before patch ==
$ time python test.py
real 0m0.986s
user 0m0.279s
sys 0m0.707s
== After patch ==
$ time python test.py
real 0m0.932s
user 0m0.261s
sys 0m0.669s
$ perf record -g python test.py
== Before patch ==
- 47.35% 3.38% python [kernel.kallsyms] [k] show_map_vma.isra.23
- 43.97% show_map_vma.isra.23
+ 20.84% seq_path
- 15.73% show_vma_header_prefix
+ 6.96% seq_pad
+ 2.94% __GI___libc_read
== After patch ==
- 44.01% 0.34% python [kernel.kallsyms] [k] show_pid_map
- 43.67% show_pid_map
- 42.91% show_map_vma.isra.23
+ 21.55% seq_path
- 15.68% show_vma_header_prefix
+ 2.08% seq_pad
0.55% seq_putc
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrei Vagin <avagin@openvz.org>
---
fs/seq_file.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/fs/seq_file.c b/fs/seq_file.c
index fb37ec42fae2..0ee52a372b66 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -829,8 +829,14 @@ EXPORT_SYMBOL(seq_write);
void seq_pad(struct seq_file *m, char c)
{
int size = m->pad_until - m->count;
- if (size > 0)
- seq_printf(m, "%*s", size, "");
+ if (size > 0) {
+ if (size + m->count > m->size) {
+ seq_set_overflow(m);
+ return;
+ }
+ memset(m->buf + m->count, ' ', size);
+ m->count += size;
+ }
if (c)
seq_putc(m, c);
}
--
2.13.6
next prev parent reply other threads:[~2018-01-12 18:58 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-12 18:58 [PATCH 1/2] procfs: add seq_put_hex_ll to speed up /proc/pid/maps Andrei Vagin
2018-01-12 18:58 ` Andrei Vagin [this message]
2018-01-12 23:33 ` Andrew Morton
2018-01-15 7:04 ` Andrei Vagin
2018-01-17 8:20 ` [PATCH v2] " Andrei Vagin
2018-02-09 13:48 ` Alexey Dobriyan
2018-02-10 7:50 ` Andrei Vagin
2018-02-12 22:15 ` Alexey Dobriyan
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