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| author | Rasmus Villemoes <linux@rasmusvillemoes.dk> | 2016-12-12 16:45:25 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-12-12 18:55:09 -0800 |
| commit | 209b14dc030760d3a17029a5c3bd92c9d6fd3f37 (patch) | |
| tree | 3c48f90dea40257ef96b2a64d3d405a84a5a7376 | |
| parent | 492b2da6056e7051917516368e75e062422c3557 (diff) | |
| download | linux-209b14dc030760d3a17029a5c3bd92c9d6fd3f37.tar.bz2 | |
fs/proc/array.c: slightly improve render_sigset_t
format_decode and vsnprintf occasionally show up in perf top, so I went
looking for places that might not need the full printf power. With the
help of kprobes, I gathered some statistics on which format strings we
mostly pass to vsnprintf. On a trivial desktop workload, I hit "%x" 25%
of the time, so something apparently reads /proc/pid/status (which does
5*16 printf("%x") calls) a lot.
With this patch, reading /proc/pid/status is 30% faster according to
this microbenchmark:
char buf[4096];
int i, fd;
for (i = 0; i < 10000; ++i) {
fd = open("/proc/self/status", O_RDONLY);
read(fd, buf, sizeof(buf));
close(fd);
}
Link: http://lkml.kernel.org/r/1474410485-1305-1-git-send-email-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Andrei Vagin <avagin@openvz.org>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | fs/proc/array.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/proc/array.c b/fs/proc/array.c index 082676ab4878..51a4213afa2e 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -245,7 +245,7 @@ void render_sigset_t(struct seq_file *m, const char *header, if (sigismember(set, i+2)) x |= 2; if (sigismember(set, i+3)) x |= 4; if (sigismember(set, i+4)) x |= 8; - seq_printf(m, "%x", x); + seq_putc(m, hex_asc[x]); } while (i >= 4); seq_putc(m, '\n'); |