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Bottomley" , Alexander Lobakin , Alexander Shishkin , Alexey Klimov , Andrea Merello , Andy Shevchenko , Arnaldo Carvalho de Melo , Arnd Bergmann , Ben Gardon , Benjamin Herrenschmidt , Brian Cain , Catalin Marinas , Christoph Lameter , Daniel Bristot de Oliveira , David Hildenbrand , Dennis Zhou , Geert Uytterhoeven , Heiko Carstens , Ian Rogers , Ingo Molnar , Jaegeuk Kim , Jakub Kicinski , Jiri Olsa , Joe Perches , Jonas Bonn , Leo Yan , Mark Rutland , Namhyung Kim , Palmer Dabbelt , Paolo Bonzini , Peter Xu , Peter Zijlstra , Petr Mladek , Rasmus Villemoes , Rich Felker , Samuel Mendoza-Jonas , Sean Christopherson , Sergey Senozhatsky , Shuah Khan , Stefan Kristiansson , Steven Rostedt , Tejun Heo , Thomas Bogendoerfer , Ulf Hansson , Will Deacon , Wolfram Sang , Yoshinori Sato , Yury Norov Subject: [PATCH 17/17] vsprintf: rework bitmap_list_string Date: Sat, 14 Aug 2021 14:17:13 -0700 Message-Id: <20210814211713.180533-18-yury.norov@gmail.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210814211713.180533-1-yury.norov@gmail.com> References: <20210814211713.180533-1-yury.norov@gmail.com> MIME-Version: 1.0 X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 930C1B259 X-Stat-Signature: 78qtyir6xa17jgrgyjje6akw9gnnnxby Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=gmail.com header.s=20161025 header.b=RV62ISfX; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf22.hostedemail.com: domain of yurynorov@gmail.com designates 209.85.214.181 as permitted sender) smtp.mailfrom=yurynorov@gmail.com X-HE-Tag: 1628975968-179466 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 Tested-by: Wolfram Sang --- lib/vsprintf.c | 24 +++++++----------------- 1 file changed, 7 insertions(+), 17 deletions(-) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index dd006adfe853..29a384eee286 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -1241,20 +1241,13 @@ char *bitmap_list_string(char *buf, char *end, un= signed long *bitmap, struct printf_spec spec, const char *fmt) { int nr_bits =3D max_t(int, spec.field_width, 0); - /* current bit is 'cur', most recently seen range is [rbot, rtop] */ - int cur, rbot, rtop; bool first =3D true; + int rbot, rtop; =20 if (check_pointer(&buf, end, bitmap, spec)) return buf; =20 - rbot =3D cur =3D find_first_bit(bitmap, nr_bits); - while (cur < nr_bits) { - rtop =3D cur; - cur =3D find_next_bit(bitmap, nr_bits, cur + 1); - if (cur < nr_bits && cur <=3D rtop + 1) - continue; - + for_each_set_bitrange(rbot, rtop, bitmap, nr_bits) { if (!first) { if (buf < end) *buf =3D ','; @@ -1263,15 +1256,12 @@ char *bitmap_list_string(char *buf, char *end, un= signed long *bitmap, first =3D false; =20 buf =3D number(buf, end, rbot, default_dec_spec); - if (rbot < rtop) { - if (buf < end) - *buf =3D '-'; - buf++; - - buf =3D number(buf, end, rtop, default_dec_spec); - } + if (rtop =3D=3D rbot + 1) + continue; =20 - rbot =3D cur; + if (buf < end) + *buf =3D '-'; + buf =3D number(++buf, end, rtop - 1, default_dec_spec); } return buf; } --=20 2.30.2