From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul Menage" Subject: Re: [-mm] Add an owner to the mm_struct (v7) Date: Thu, 3 Apr 2008 11:56:16 -0700 Message-ID: <6599ad830804031156w79366866yed9f8c3b8acf71fb@mail.gmail.com> References: <20080403174433.26356.42121.sendpatchset@localhost.localdomain> <1207247113.21922.63.camel@nimitz.home.sr71.net> <47F52735.7090502@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <47F52735.7090502@linux.vnet.ibm.com> Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org To: balbir@linux.vnet.ibm.com Cc: Dave Hansen , Pavel Emelianov , Hugh Dickins , Sudhir Kumar , YAMAMOTO Takashi , lizf@cn.fujitsu.com, linux-kernel@vger.kernel.org, taka@valinux.co.jp, linux-mm@kvack.org, David Rientjes , Andrew Morton , KAMEZAWA Hiroyuki List-Id: linux-mm.kvack.org On Thu, Apr 3, 2008 at 11:51 AM, Balbir Singh wrote: > >> + * delay_group_leader() ensures that if the group leader is around > >> + * we need not select a new owner. > >> + */ > >> + ret = (mm && (atomic_read(&mm->mm_users) > 1) && (mm->owner == p) && > >> + !delay_group_leader(p)); > >> + return ret; > >> +} > > > > Ugh. Could you please spell this out a bit more. I find that stuff > > above really hard to read. Something like: > > > > if (!mm) > > return 0; > > if (atomic_read(&mm->mm_users) <= 1) > > return 0; > > if (mm->owner != p) > > return 0; > > if (delay_group_leader(p)) > > return 0; > > return 1; > > > > The problem with code above is 4 branch instructions and the code I have just 4 > AND operations. They'll be completely equivalent to the compiler, due to the short-circuit evaluation of && Paul