linux-kernel - Re: [Drbd-dev] [PATCH] drbd: use bitmap

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Message-ID: <20150320151450.GG3556@soda.linbit>
Date:	Fri, 20 Mar 2015 16:14:50 +0100
From:	Lars Ellenberg <lars.ellenberg@...bit.com>
To:	Akinobu Mita <akinobu.mita@...il.com>
Cc:	linux-kernel@...r.kernel.org, drbd-dev@...ts.linbit.com
Subject: Re: [Drbd-dev] [PATCH] drbd: use bitmap_weight()

On Sat, Mar 14, 2015 at 10:12:56AM +0900, Akinobu Mita wrote:
> Use bitmap_weight to count the total number of bits set in bitmap.
> This change just simplifies the code a bit.

"Simplifies", not sure about that, but ok, maybe.

For the "bm_set_full_words_within_one_page", I disagree.
I think it is more cpu cache friendly to hweight_long then set to ~0UL
each word in turn, than to first bitmap_weight() all words, then
bitmap_fill() all words.

Thanks,

	Lars Ellenberg

BTW, you swapped names and email addresses of phil and me.  Are those
listed incorrectly somewhere, or was that just a mishap on your part?
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