From: Johannes Berg <johannes@sipsolutions.net>
To: Zeng Zhaoxiu <zhaoxiu.zeng@gmail.com>, davem@davemloft.net
Cc: linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] mac80211: improve the contiguous mask checking
Date: Thu, 17 Dec 2015 16:04:28 +0100 [thread overview]
Message-ID: <1450364668.8247.34.camel@sipsolutions.net> (raw)
In-Reply-To: <1450364392-76874-1-git-send-email-zhaoxiu.zeng@gmail.com> (sfid-20151217_160054_877867_44DDA348)
On Thu, 2015-12-17 at 22:59 +0800, Zeng Zhaoxiu wrote:
> If the result of adding the first set bit to the mask is power of 2,
> the mask must be contiguous. "mask & -mask" can get the first set bit
> of mask gracefully.
> - if (__ffs64(mask) + hweight64(mask) != fls64(mask))
> {
> + inc = (mask & -mask);
> + val = mask + inc;
> + if ((val & (val - 1)) != 0) {
> /* not a contiguous mask ... not handled now! */
Hm. Ok, I can see how that would work, but it doesn't really seem like
much of an "improvement" to me? Surely I seem to need much more
thinking to understand this. There's no reason to optimise it either,
so why should we change it?
johannes
prev parent reply other threads:[~2015-12-17 15:04 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-17 14:59 [PATCH 1/1] mac80211: improve the contiguous mask checking Zeng Zhaoxiu
2015-12-17 15:04 ` Johannes Berg [this message]
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