linux-kernel - Re: [RFC] change non-atomic bitops method

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Message-Id: <20150203.004031.593368249759204527.davem@davemloft.net>
Date:	Tue, 03 Feb 2015 00:40:31 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	akpm@...ux-foundation.org
Cc:	Yalin.Wang@...ymobile.com, kirill@...temov.name, arnd@...db.de,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux@....linux.org.uk, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC] change non-atomic bitops method

From: Andrew Morton <akpm@...ux-foundation.org>
Date: Mon, 2 Feb 2015 22:38:51 -0800

> It is only with both these ratios that we can work out whether the
> patch is a net gain.  My suspicion is that set_bit on an already-set
> bit is so rare that the patch will be a loss.

A common pattern is implementing a "referenced" bit, and in that case
the bit is often already set, and in such a scenerio the proposed
change is a huge win.

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