From d1be35cb6f96975d792a1535d3fe9b75239065ee Mon Sep 17 00:00:00 2001 From: Andrei Vagin Date: Tue, 10 Apr 2018 16:31:16 -0700 Subject: proc: add seq_put_decimal_ull_width to speed up /proc/pid/smaps seq_put_decimal_ull_w(m, str, val, width) prints a decimal number with a specified minimal field width. It is equivalent of seq_printf(m, "%s%*d", str, width, val), but it works much faster. == test_smaps.py num = 0 with open("/proc/1/smaps") as f: for x in xrange(10000): data = f.read() f.seek(0, 0) == == Before patch == $ time python test_smaps.py real 0m4.593s user 0m0.398s sys 0m4.158s == After patch == $ time python test_smaps.py real 0m3.828s user 0m0.413s sys 0m3.408s $ perf -g record python test_smaps.py == Before patch == - 79.01% 3.36% python [kernel.kallsyms] [k] show_smap.isra.33 - 75.65% show_smap.isra.33 + 48.85% seq_printf + 15.75% __walk_page_range + 9.70% show_map_vma.isra.23 0.61% seq_puts == After patch == - 75.51% 4.62% python [kernel.kallsyms] [k] show_smap.isra.33 - 70.88% show_smap.isra.33 + 24.82% seq_put_decimal_ull_w + 19.78% __walk_page_range + 12.74% seq_printf + 11.08% show_map_vma.isra.23 + 1.68% seq_puts [akpm@linux-foundation.org: fix drivers/of/unittest.c build] Link: http://lkml.kernel.org/r/20180212074931.7227-1-avagin@openvz.org Signed-off-by: Andrei Vagin Cc: Alexey Dobriyan Cc: KAMEZAWA Hiroyuki Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/vsprintf.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) (limited to 'lib/vsprintf.c') diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 89f8a4a4b770..30c0cb8cc9bc 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -336,7 +336,7 @@ char *put_dec(char *buf, unsigned long long n) * * If speed is not important, use snprintf(). It's easy to read the code. */ -int num_to_str(char *buf, int size, unsigned long long num) +int num_to_str(char *buf, int size, unsigned long long num, unsigned int width) { /* put_dec requires 2-byte alignment of the buffer. */ char tmp[sizeof(num) * 3] __aligned(2); @@ -350,11 +350,21 @@ int num_to_str(char *buf, int size, unsigned long long num) len = put_dec(tmp, num) - tmp; } - if (len > size) + if (len > size || width > size) return 0; + + if (width > len) { + width = width - len; + for (idx = 0; idx < width; idx++) + buf[idx] = ' '; + } else { + width = 0; + } + for (idx = 0; idx < len; ++idx) - buf[idx] = tmp[len - idx - 1]; - return len; + buf[idx + width] = tmp[len - idx - 1]; + + return len + width; } #define SIGN 1 /* unsigned/signed, must be 1 */ -- cgit v1.2.3-55-g7522