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From: Yury Norov <yury.norov@gmail.com>
To: linux-m68k@lists.linux-m68k.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-sh@vger.kernel.org, linux-arch@vger.kernel.org
Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Rich Felker <dalias@libc.org>, Arnd Bergmann <arnd@arndb.de>,
	Dennis Zhou <dennis@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Wolfram Sang <wsa+renesas@sang-engineering.com>,
	David Sterba <dsterba@suse.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Stefano Brivio <sbrivio@redhat.com>,
	"Ma, Jianpeng" <jianpeng.ma@intel.com>,
	Wei Yang <richard.weiyang@linux.alibaba.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Subject: Re: [PATCH 0/6] lib/find_bit: fast path for small bitmaps
Date: Fri, 29 Jan 2021 12:51:32 -0800	[thread overview]
Message-ID: <CAAH8bW8cZYG0HxqVAK4HxZDP3abxkHXsqfhSzJ-amQ_S6yDY_w@mail.gmail.com> (raw)
In-Reply-To: <20210129204528.2118168-1-yury.norov@gmail.com>

On Fri, Jan 29, 2021 at 12:45 PM Yury Norov <yury.norov@gmail.com> wrote:
>
> Bitmap operations are much simpler and faster in case of small bitmaps, whicn
> fit into a single word. In linux/bitmap.h we have a machinery that allows
> compiler to replace actual function call with a few instructions if bitmaps
> passed into the function is small and its size is known at compile time.
>
> find_*_bit() API lacks this functionality; despite users will benefit from it
> a lot. One important example is cpumask subsystem, when NR_CPUS <= BITS_PER_LONG.
> In the very best case, the compiler may replace a find_*_bit() call for such a
> bitmap with a single ffs or ffz instruction.
>
> Tools is synchronized with new implementation where needed.

Sorry for the broken enumeration . If it's too confusing, please let me know
and I'll resend.

  parent reply	other threads:[~2021-01-29 20:53 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-29 20:45 [PATCH 0/6] lib/find_bit: fast path for small bitmaps Yury Norov
2021-01-29 20:45 ` [PATCH 1/6] arch: rearrange headers inclusion order in asm/bitops for m68k and sh Yury Norov
2021-01-29 20:45 ` [PATCH 2/6] lib: inttroduce BITS_{FIRST,LAST}() macro Yury Norov
2021-01-29 20:45 ` [PATCH 2/5] bits_per_long.h: introduce SMALL_CONST() macro Yury Norov
2021-01-29 21:10   ` Andy Shevchenko
2021-01-29 21:24     ` Joe Perches
2021-01-29 21:28     ` Yury Norov
2021-01-29 22:25     ` Yury Norov
2021-01-29 20:45 ` [PATCH 3/5] lib: inline _find_next_bit() wrappers Yury Norov
2021-01-29 20:45 ` [PATCH 4/5] lib: add fast path for find_next_*_bit() Yury Norov
2021-01-29 20:45 ` [PATCH 6/6] lib: add fast path for find_first_*_bit() and find_last_bit() Yury Norov
2021-01-29 20:51 ` Yury Norov [this message]
2021-01-29 21:12   ` [PATCH 0/6] lib/find_bit: fast path for small bitmaps Andy Shevchenko
  -- strict thread matches above, loose matches on Subject: below --
2021-01-21  0:06 Yury Norov

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