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authorRasmus Villemoes <linux@rasmusvillemoes.dk>2016-12-12 16:45:25 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-12-12 18:55:09 -0800
commit209b14dc030760d3a17029a5c3bd92c9d6fd3f37 (patch)
tree3c48f90dea40257ef96b2a64d3d405a84a5a7376
parent492b2da6056e7051917516368e75e062422c3557 (diff)
downloadop-kernel-dev-209b14dc030760d3a17029a5c3bd92c9d6fd3f37.zip
op-kernel-dev-209b14dc030760d3a17029a5c3bd92c9d6fd3f37.tar.gz
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.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 082676a..51a4213 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');
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