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authorYury Norov <yury.norov@gmail.com>2021-08-14 14:17:13 -0700
committerYury Norov <yury.norov@gmail.com>2022-01-15 08:47:31 -0800
commit15325b4f768f2b27b5765489eeab6ec0d6b5e902 (patch)
treef29491038480dcf4575c84207f8f7ad2557f21d6 /lib/vsprintf.c
parentdb7313005e9c2d4e80888dd18d4a83926b920e8c (diff)
downloadlwn-15325b4f768f2b27b5765489eeab6ec0d6b5e902.tar.gz
lwn-15325b4f768f2b27b5765489eeab6ec0d6b5e902.zip
vsprintf: rework bitmap_list_string
bitmap_list_string() is very ineffective when printing bitmaps with long ranges of set bits because it calls find_next_bit for each bit in the bitmap. We can do better by detecting ranges of set bits. In my environment, before/after is 943008/31008 ns. Signed-off-by: Yury Norov <yury.norov@gmail.com> Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Diffstat (limited to 'lib/vsprintf.c')
-rw-r--r--lib/vsprintf.c24
1 files changed, 7 insertions, 17 deletions
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 58d5e567f836..d4b4e481045b 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1241,20 +1241,13 @@ char *bitmap_list_string(char *buf, char *end, unsigned long *bitmap,
struct printf_spec spec, const char *fmt)
{
int nr_bits = max_t(int, spec.field_width, 0);
- /* current bit is 'cur', most recently seen range is [rbot, rtop] */
- int cur, rbot, rtop;
bool first = true;
+ int rbot, rtop;
if (check_pointer(&buf, end, bitmap, spec))
return buf;
- rbot = cur = find_first_bit(bitmap, nr_bits);
- while (cur < nr_bits) {
- rtop = cur;
- cur = find_next_bit(bitmap, nr_bits, cur + 1);
- if (cur < nr_bits && cur <= rtop + 1)
- continue;
-
+ for_each_set_bitrange(rbot, rtop, bitmap, nr_bits) {
if (!first) {
if (buf < end)
*buf = ',';
@@ -1263,15 +1256,12 @@ char *bitmap_list_string(char *buf, char *end, unsigned long *bitmap,
first = false;
buf = number(buf, end, rbot, default_dec_spec);
- if (rbot < rtop) {
- if (buf < end)
- *buf = '-';
- buf++;
-
- buf = number(buf, end, rtop, default_dec_spec);
- }
+ if (rtop == rbot + 1)
+ continue;
- rbot = cur;
+ if (buf < end)
+ *buf = '-';
+ buf = number(++buf, end, rtop - 1, default_dec_spec);
}
return buf;
}