| Message ID | 20180112185812.7710-2-avagin@openvz.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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); }
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(-)