linux-kernel - Re: [PATCH] bitmap: optimize bitmap

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Message-ID: <ZN3qlCd+TcYiZg+s@smile.fi.intel.com>
Date:   Thu, 17 Aug 2023 12:38:28 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Yury Norov <yury.norov@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: Re: [PATCH] bitmap: optimize bitmap_remap()

On Thu, Aug 17, 2023 at 12:37:05PM +0300, Andy Shevchenko wrote:
> On Tue, Aug 15, 2023 at 04:59:34PM -0700, Yury Norov wrote:

...

> >  		int n = bitmap_pos_to_ord(old, oldbit, nbits);
> >  
> > +		bit = (n < 0) ? oldbit :	/* identity map */
> 
> Can't you also optimize this case?
> 
> Something like
> 
>   bitmap_xor(tmp, old, new) // maybe even better approach, dunno

>   bitmap_empty(tmp) // can be replaced by find first bit

Or reuse bitmap_weight()...

> ?

-- 
With Best Regards,
Andy Shevchenko