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From: Andrew Morton <akpm@linux-foundation.org>
To: Glauber Costa <glommer@parallels.com>
Cc: <linux-mm@kvack.org>, <cgroups@vger.kernel.org>,
	<devel@openvz.org>, <kamezawa.hiroyu@jp.fujitsu.com>,
	<netdev@vger.kernel.org>, Tejun Heo <tj@kernel.org>,
	Li Zefan <lizefan@huawei.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@suse.cz>, David Miller <davem@davemloft.net>
Subject: Re: [PATCH v6 2/2] decrement static keys on real destroy time
Date: Wed, 23 May 2012 13:33:54 -0700	[thread overview]
Message-ID: <20120523133354.373f1bb4.akpm@linux-foundation.org> (raw)
In-Reply-To: <4FBCAAF4.4030803@parallels.com>

On Wed, 23 May 2012 13:16:36 +0400
Glauber Costa <glommer@parallels.com> wrote:

> On 05/23/2012 02:46 AM, Andrew Morton wrote:
> > Here, we're open-coding kinda-test_bit().  Why do that?  These flags are
> > modified with set_bit() and friends, so we should read them with the
> > matching test_bit()?
> 
> My reasoning was to be as cheap as possible, as you noted yourself two
> paragraphs below.

These aren't on any fast path, are they?

Plus: you failed in that objective!  The C compiler's internal
scalar->bool conversion makes these functions no more efficient than
test_bit().

> > So here are suggested changes from*some*  of the above discussion.
> > Please consider, incorporate, retest and send us a v7?
> 
> How do you want me to do it? Should I add your patch ontop of mine,
> and then another one that tweaks whatever else is left, or should I just
> merge those changes into the patches I have?

A brand new patch, I guess.  I can sort out the what-did-he-change view
at this end.

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      reply	other threads:[~2012-05-23 20:33 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-22 10:25 [PATCH v6 0/2] fix static_key disabling problem in memcg Glauber Costa
2012-05-22 10:25 ` [PATCH v6 1/2] Always free struct memcg through schedule_work() Glauber Costa
2012-05-22 10:25 ` [PATCH v6 2/2] decrement static keys on real destroy time Glauber Costa
     [not found]   ` <1337682339-21282-3-git-send-email-glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
2012-05-22 22:46     ` Andrew Morton
     [not found]       ` <20120522154610.f2f9b78e.akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2012-05-22 23:11         ` Andrew Morton
2012-05-23  9:16         ` Glauber Costa
2012-05-23 20:33           ` Andrew Morton [this message]

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