From: Yury Norov <yury.norov@gmail.com>
To: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
Cc: linux-kernel@vger.kernel.org,
"James E.J. Bottomley" <jejb@linux.ibm.com>,
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Subject: Re: [PATCH 2/9] lib/bitmap: implement bitmap_{empty,full} with bitmap_weight_eq()
Date: Sat, 27 Nov 2021 22:27:27 -0800 [thread overview]
Message-ID: <20211128062727.GA276670@lapt> (raw)
In-Reply-To: <YaMHfzZ5PBn0714Z@qmqm.qmqm.pl>
On Sun, Nov 28, 2021 at 05:37:19AM +0100, Michał Mirosław wrote:
> On Sat, Nov 27, 2021 at 07:56:57PM -0800, Yury Norov wrote:
> > Now as we have bitmap_weight_eq(), switch bitmap_full() and
> > bitmap_empty() to using it.
> [...]
> > -static inline bool bitmap_empty(const unsigned long *src, unsigned nbits)
> > -{
> > - if (small_const_nbits(nbits))
> > - return ! (*src & BITMAP_LAST_WORD_MASK(nbits));
> > -
> > - return find_first_bit(src, nbits) == nbits;
> > -}
> [...]
> > +static __always_inline bool bitmap_empty(const unsigned long *src, unsigned int nbits)
> > +{
> > + return bitmap_weight_eq(src, nbits, 0);
> > +}
> [..]
>
> What's the speed difference? Have you benchmarked this?
bitmap_weight_eq() should be faster than find_first_bit(), but the
difference is few cycles, so I didn't bother measuring it.
New version looks just better.
next prev parent reply other threads:[~2021-11-28 6:29 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-28 3:56 [PATCH 0/9] lib/bitmap: optimize bitmap_weight() usage Yury Norov
2021-11-28 3:56 ` [PATCH 1/9] lib/bitmap: add bitmap_weight_{eq,gt,le} Yury Norov
2021-11-28 3:56 ` [PATCH 2/9] lib/bitmap: implement bitmap_{empty,full} with bitmap_weight_eq() Yury Norov
2021-11-28 4:37 ` Michał Mirosław
2021-11-28 6:27 ` Yury Norov [this message]
2021-11-28 18:10 ` Michał Mirosław
2021-12-14 19:43 ` Yury Norov
2021-12-15 8:40 ` David Laight
2021-12-15 17:45 ` Yury Norov
2021-11-28 3:56 ` [PATCH 3/9] all: replace bitmap_weigth() with bitmap_{empty,full,eq,gt,le} Yury Norov
2021-11-28 4:47 ` Michał Mirosław
2021-11-28 8:01 ` Greg Kroah-Hartman
2021-11-28 3:56 ` [PATCH 4/9] tools: sync bitmap_weight() usage with the kernel Yury Norov
2021-11-28 3:57 ` [PATCH 5/9] lib/cpumask: add cpumask_weight_{eq,gt,le} Yury Norov
2021-11-28 3:57 ` [PATCH 6/9] lib/nodemask: add nodemask_weight_{eq,gt,le} Yury Norov
2021-11-28 3:57 ` [PATCH 7/9] lib/cpumask: add num_{possible,present,active}_cpus_{eq,gt,le} Yury Norov
2021-11-28 4:56 ` Michał Mirosław
2021-11-28 5:09 ` Michał Mirosław
2021-11-28 6:34 ` Yury Norov
2021-11-28 17:07 ` Joe Perches
2021-11-28 17:43 ` Yury Norov
2021-11-28 17:54 ` Dennis Zhou
2021-11-28 18:47 ` Yury Norov
2021-11-28 17:56 ` Emil Renner Berthing
2021-11-28 17:57 ` Joe Perches
2021-11-28 3:57 ` [PATCH 8/9] lib/nodemask: add num_node_state_eq() Yury Norov
2021-11-28 3:57 ` [PATCH 9/9] MAINTAINERS: add cpumask and nodemask files to BITMAP_API Yury Norov
2021-11-28 11:08 ` [PATCH 0/9] lib/bitmap: optimize bitmap_weight() usage Nicholas Piggin
2021-11-28 23:36 ` Yury Norov
2021-11-28 18:03 ` mirq-test
2021-11-28 18:05 ` Michał Mirosław
2021-11-29 6:38 ` Yury Norov
2021-11-29 16:34 ` Michał Mirosław
2021-12-02 0:31 ` Yury Norov
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