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Date: Wed, 15 Dec 2021 09:45:30 -0800
From: Yury Norov <yury.norov@...il.com>
To: David Laight <David.Laight@...lab.com>
Cc: Michał Mirosław <mirq-linux@...e.qmqm.pl>,
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"James E.J. Bottomley" <jejb@...ux.ibm.com>,
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Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
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Subject: Re: [PATCH 2/9] lib/bitmap: implement bitmap_{empty,full} with bitmap_weight_eq()
On Wed, Dec 15, 2021 at 12:41 AM David Laight <David.Laight@...lab.com> wrote:
>
> From: Yury Norov
> > Sent: 14 December 2021 19:43
> ...
> >
> > I think that for long bitmaps the most time consuming operation is moving
> > data to L1, and for short bitmaps the difference between approaches is
> > barely measurable.
> >
> > But hweght_long on each iteration can't be more effective than the current
> > version. So, I'll drop this patch for v2 and keep things unchanged.
>
> Actually do bitmap_full/empty() calls make any sense at all?
> The result is stale since bitmaps are designed to do locked operations.
> If you have a lock covering the bitmap then you should be using
> something that uses non-locked accesses.
> Rightly or wrongly that isn't the bitmap api.
Are you talking about __{set,clear}_bit()?
include/asm-generic/bitops/non-atomic.h
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