linux-kernel - Re: [PATCH 33/54] net: ethernet: replace bitmap_weight with bitmap_weight

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Date:   Tue, 8 Feb 2022 22:46:43 -0800
From:   Yury Norov <yury.norov@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        David Laight <David.Laight@...lab.com>,
        Joe Perches <joe@...ches.com>, Dennis Zhou <dennis@...nel.org>,
        Emil Renner Berthing <kernel@...il.dk>,
        Nicholas Piggin <npiggin@...il.com>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Alexey Klimov <aklimov@...hat.com>,
        linux-kernel@...r.kernel.org, Sunil Goutham <sgoutham@...vell.com>,
        Geetha sowjanya <gakula@...vell.com>,
        Subbaraya Sundeep <sbhatta@...vell.com>,
        hariprasad <hkelam@...vell.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH 33/54] net: ethernet: replace bitmap_weight with
 bitmap_weight_{eq,gt,ge,lt,le} for mellanox

On Mon, Jan 24, 2022 at 02:48:12PM +0200, Andy Shevchenko wrote:
> On Sun, Jan 23, 2022 at 10:39:04AM -0800, Yury Norov wrote:
> > Mellanox code uses bitmap_weight() to compare the weight of bitmap with
> > a given number. We can do it more efficiently with bitmap_weight_{eq, ...}
> > because conditional bitmap_weight may stop traversing the bitmap earlier,
> > as soon as condition is met.
> 
> > -	if (port <= 0 || port > m)
> > +	if (port <= 0 || bitmap_weight_lt(actv_ports.ports, dev->caps.num_ports, port))
> >  		return -EINVAL;
> 
> Can we eliminate now the port <= 0 check? Or at least make it port == 0?

The port is a parameter of exported function. I'd rather not take this risk.
Even if it makes sense, it should be a separate patch anyways.