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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 05/17] lib: add find_first_and_bit() Date: Sat, 14 Aug 2021 14:17:01 -0700 Message-Id: <20210814211713.180533-6-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-Queue-Id: D4E7BD00802A Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=gmail.com header.s=20161025 header.b=bb0tqNc4; spf=pass (imf15.hostedemail.com: domain of yurynorov@gmail.com designates 209.85.216.47 as permitted sender) smtp.mailfrom=yurynorov@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspamd-Server: rspam01 X-Stat-Signature: bpef4nz6wrpqg9ob6ze5bkw9nsdwui56 X-HE-Tag: 1628975879-670015 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: Currently find_first_and_bit() is an alias to find_next_and_bit(). Howeve= r, it is widely used in cpumask, so it worth to optimize it. This patch adds its own implementation for find_first_and_bit(). On x86_64 find_bit_benchmark says: Before (#define find_first_and_bit(...) find_next_and_bit(..., 0): Start testing find_bit() with random-filled bitmap [ 140.291468] find_first_and_bit: 46890919 ns, 32671 iteratio= ns Start testing find_bit() with sparse bitmap [ 140.295028] find_first_and_bit: 7103 ns, 1 iteratio= ns After: Start testing find_bit() with random-filled bitmap [ 162.574907] find_first_and_bit: 25045813 ns, 32846 iteratio= ns Start testing find_bit() with sparse bitmap [ 162.578458] find_first_and_bit: 4900 ns, 1 iteratio= ns (Thanks to Alexey Klimov for thorough testing.) Signed-off-by: Yury Norov Tested-by: Wolfram Sang Tested-by: Alexey Klimov --- include/linux/find.h | 27 +++++++++++++++++++++++++++ lib/find_bit.c | 21 +++++++++++++++++++++ lib/find_bit_benchmark.c | 21 +++++++++++++++++++++ 3 files changed, 69 insertions(+) diff --git a/include/linux/find.h b/include/linux/find.h index ea57f7f38c49..6048f8c97418 100644 --- a/include/linux/find.h +++ b/include/linux/find.h @@ -12,6 +12,8 @@ extern unsigned long _find_next_bit(const unsigned long= *addr1, const unsigned long *addr2, unsigned long nbits, unsigned long start, unsigned long invert, unsigned long le); extern unsigned long _find_first_bit(const unsigned long *addr, unsigned= long size); +extern unsigned long _find_first_and_bit(const unsigned long *addr1, + const unsigned long *addr2, unsigned long size); extern unsigned long _find_first_zero_bit(const unsigned long *addr, uns= igned long size); extern unsigned long _find_last_bit(const unsigned long *addr, unsigned = long size); =20 @@ -123,6 +125,31 @@ unsigned long find_first_bit(const unsigned long *ad= dr, unsigned long size) } #endif =20 +#ifndef find_first_and_bit +/** + * find_first_and_bit - find the first set bit in both memory regions + * @addr1: The first address to base the search on + * @addr2: The second address to base the search on + * @size: The bitmap size in bits + * + * Returns the bit number for the next set bit + * If no bits are set, returns @size. + */ +static inline +unsigned long find_first_and_bit(const unsigned long *addr1, + const unsigned long *addr2, + unsigned long size) +{ + if (small_const_nbits(size)) { + unsigned long val =3D *addr1 & *addr2 & GENMASK(size - 1, 0); + + return val ? __ffs(val) : size; + } + + return _find_first_and_bit(addr1, addr2, size); +} +#endif + #ifndef find_first_zero_bit /** * find_first_zero_bit - find the first cleared bit in a memory region diff --git a/lib/find_bit.c b/lib/find_bit.c index 0f8e2e369b1d..1b8e4b2a9cba 100644 --- a/lib/find_bit.c +++ b/lib/find_bit.c @@ -89,6 +89,27 @@ unsigned long _find_first_bit(const unsigned long *add= r, unsigned long size) EXPORT_SYMBOL(_find_first_bit); #endif =20 +#ifndef find_first_and_bit +/* + * Find the first set bit in two memory regions. + */ +unsigned long _find_first_and_bit(const unsigned long *addr1, + const unsigned long *addr2, + unsigned long size) +{ + unsigned long idx, val; + + for (idx =3D 0; idx * BITS_PER_LONG < size; idx++) { + val =3D addr1[idx] & addr2[idx]; + if (val) + return min(idx * BITS_PER_LONG + __ffs(val), size); + } + + return size; +} +EXPORT_SYMBOL(_find_first_and_bit); +#endif + #ifndef find_first_zero_bit /* * Find the first cleared bit in a memory region. diff --git a/lib/find_bit_benchmark.c b/lib/find_bit_benchmark.c index 5637c5711db9..db904b57d4b8 100644 --- a/lib/find_bit_benchmark.c +++ b/lib/find_bit_benchmark.c @@ -49,6 +49,25 @@ static int __init test_find_first_bit(void *bitmap, un= signed long len) return 0; } =20 +static int __init test_find_first_and_bit(void *bitmap, const void *bitm= ap2, unsigned long len) +{ + static DECLARE_BITMAP(cp, BITMAP_LEN) __initdata; + unsigned long i, cnt; + ktime_t time; + + bitmap_copy(cp, bitmap, BITMAP_LEN); + + time =3D ktime_get(); + for (cnt =3D i =3D 0; i < len; cnt++) { + i =3D find_first_and_bit(cp, bitmap2, len); + __clear_bit(i, cp); + } + time =3D ktime_get() - time; + pr_err("find_first_and_bit: %18llu ns, %6ld iterations\n", time, cnt); + + return 0; +} + static int __init test_find_next_bit(const void *bitmap, unsigned long l= en) { unsigned long i, cnt; @@ -129,6 +148,7 @@ static int __init find_bit_test(void) * traverse only part of bitmap to avoid soft lockup. */ test_find_first_bit(bitmap, BITMAP_LEN / 10); + test_find_first_and_bit(bitmap, bitmap2, BITMAP_LEN / 2); test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN); =20 pr_err("\nStart testing find_bit() with sparse bitmap\n"); @@ -145,6 +165,7 @@ static int __init find_bit_test(void) test_find_next_zero_bit(bitmap, BITMAP_LEN); test_find_last_bit(bitmap, BITMAP_LEN); test_find_first_bit(bitmap, BITMAP_LEN); + test_find_first_and_bit(bitmap, bitmap2, BITMAP_LEN); test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN); =20 /* --=20 2.30.2