diff options
author | Andrei Vagin <avagin@openvz.org> | 2018-04-10 16:30:47 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-04-11 10:28:32 -0700 |
commit | 8cfa67b4d9a9d9a6061f3cfd0e0ed16e66e45984 (patch) | |
tree | cf95174279e04babd3bc9feb8f64179ca7257259 /fs/seq_file.c | |
parent | 0e3dc019143104a6e676287b1e453cccd7add404 (diff) | |
download | op-kernel-dev-8cfa67b4d9a9d9a6061f3cfd0e0ed16e66e45984.zip op-kernel-dev-8cfa67b4d9a9d9a6061f3cfd0e0ed16e66e45984.tar.gz |
procfs: optimize seq_pad() to speed up /proc/pid/maps
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
Link: http://lkml.kernel.org/r/20180112185812.7710-2-avagin@openvz.org
Signed-off-by: Andrei Vagin <avagin@openvz.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/seq_file.c')
-rw-r--r-- | fs/seq_file.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/fs/seq_file.c b/fs/seq_file.c index cde1bdb..3714ae1 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -828,8 +828,14 @@ 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); } |