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Date: Thu, 8 Jul 2021 20:45:19 -0700 From: Yury Norov <yury.norov@...il.com> To: linux-kernel@...r.kernel.org Cc: Yury Norov <yury.norov@...il.com>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Rasmus Villemoes <linux@...musvillemoes.dk>, Petr Mladek <pmladek@...e.com>, Steven Rostedt <rostedt@...dmis.org>, Sergey Senozhatsky <senozhatsky@...omium.org>, Tejun Heo <tj@...nel.org> Subject: [PATCH 2/2] bitmap: introduce for_each_set_bitrange bitmap_list_string() is very ineffective when printing bitmaps with long ranges of set bits because it calls find_next_bit for each bit. We can do better by detecting ranges of set bits. This patch introduces a macro for_each_set_bitrange and uses it in bitmap_list_string(). In my environment, before/after is 943008/31008 ns. Signed-off-by: Yury Norov <yury.norov@...il.com> --- include/linux/find.h | 7 +++++++ lib/vsprintf.c | 40 ++++++++++++++++------------------------ 2 files changed, 23 insertions(+), 24 deletions(-) diff --git a/include/linux/find.h b/include/linux/find.h index ae9ed52b52b8..1a5ed45dc81b 100644 --- a/include/linux/find.h +++ b/include/linux/find.h @@ -301,6 +301,13 @@ unsigned long find_next_bit_le(const void *addr, unsigned (bit) < (size); \ (bit) = find_next_zero_bit((addr), (size), (bit) + 1)) +#define for_each_set_bitrange(b, e, addr, size) \ + for ((b) = find_next_bit((addr), (size), 0), \ + (e) = find_next_zero_bit((addr), (size), (b) + 1); \ + (b) < (size); \ + (b) = find_next_bit((addr), (size), (e) + 1), \ + (e) = find_next_zero_bit((addr), (size), (b) + 1)) + /** * for_each_set_clump8 - iterate over bitmap for each 8-bit clump with set bits * @start: bit offset to start search and to store the current iteration offset diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 87acf66f0e4c..1ee54dace71e 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -1240,38 +1240,30 @@ 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; + char *start = buf; + int b, e; 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(b, e, bitmap, nr_bits) { + buf = number(buf, end, b, default_dec_spec); + if (e == b + 1) + goto put_comma; - if (!first) { - if (buf < end) - *buf = ','; - buf++; - } - first = false; + if (buf < end) + *buf = '-'; - buf = number(buf, end, rbot, default_dec_spec); - if (rbot < rtop) { - if (buf < end) - *buf = '-'; - buf++; + buf = number(++buf, end, e - 1, default_dec_spec); +put_comma: + if (buf < end) + *buf = ','; + buf++; + } - buf = number(buf, end, rtop, default_dec_spec); - } + if (buf > start) + buf--; - rbot = cur; - } return buf; } -- 2.30.2
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