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Date:   Sun, 30 Jan 2022 12:54:08 +0000
From:   Jonathan Cameron <jic23@kernel.org>
To:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc:     Yury Norov <yury.norov@gmail.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Andrew Morton <akpm@linux-foundation.org>,
        =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= <mirq-linux@rere.qmqm.pl>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        David Laight <David.Laight@aculab.com>,
        Joe Perches <joe@perches.com>, Dennis Zhou <dennis@kernel.org>,
        Emil Renner Berthing <kernel@esmil.dk>,
        Nicholas Piggin <npiggin@gmail.com>,
        Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>,
        Alexey Klimov <aklimov@redhat.com>,
        linux-kernel@vger.kernel.org, Lars-Peter Clausen <lars@metafoo.de>,
        Nathan Chancellor <nathan@kernel.org>,
        Alexandru Ardelean <alexandru.ardelean@analog.com>,
        linux-iio@vger.kernel.org
Subject: Re: [PATCH 29/54] drivers/iio: replace bitmap_weight() with
 bitmap_weight_{eq,gt} where appropriate
Message-ID: <20220130125408.0cca0b66@jic23-huawei>
In-Reply-To: <Ye6fsynB1/q0ZLui@smile.fi.intel.com>
References: <20220123183925.1052919-1-yury.norov@gmail.com>
        <20220123183925.1052919-30-yury.norov@gmail.com>
        <Ye6fsynB1/q0ZLui@smile.fi.intel.com>
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On Mon, 24 Jan 2022 14:46:43 +0200
Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> On Sun, Jan 23, 2022 at 10:39:00AM -0800, Yury Norov wrote:
> > drivers/iio calls bitmap_weight() to compare the weight of bitmap with
> > a given number. We can do it more efficiently with bitmap_weight_{eq, gt}
> > because conditional bitmap_weight may stop traversing the bitmap earlier,
> > as soon as condition is met.  
> 
> ...
> 
> >  		int i, j;
> >  
> >  		for (i = 0, j = 0;
> > -		     i < bitmap_weight(indio_dev->active_scan_mask,
> > -				       indio_dev->masklength);
> > +		     bitmap_weight_gt(indio_dev->active_scan_mask,
> > +				       indio_dev->masklength, i);
> >  		     i++, j++) {
> >  			j = find_next_bit(indio_dev->active_scan_mask,
> >  					  indio_dev->masklength, j);  
> 
> This smells like room for improvement. Have you checked this deeply?
> 

I have no idea what I was smoking that day.
It was near 10 years ago, so I'll blame my younger self ;)

Jonathan