From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: bogosort (was Re: Re: [RFC][PATCH -mm 5/6] Freezer: Use freezing timeout more efficiently) Date: Tue, 10 Jul 2007 23:39:17 +0200 Message-ID: <200707102339.18192.rjw@sisk.pl> References: <200707092229.08898.rjw@sisk.pl> <200707101204.42687.rjw@sisk.pl> <20070710211320.GC7091@elf.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20070710211320.GC7091@elf.ucw.cz> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.linux-foundation.org Errors-To: linux-pm-bounces@lists.linux-foundation.org To: Pavel Machek Cc: Matthew Garrett , linux-pm@lists.linux-foundation.org, Oleg Nesterov , Miklos Szeredi List-Id: linux-pm@vger.kernel.org Hi, On Tuesday, 10 July 2007 23:13, Pavel Machek wrote: > Hi! > > > > > No, we can't do that: > > > > > > > > Imagine we have single uninterruptible task that waits for disk. It > > > > would exit uninterruptible state in 10msec, *but* you give up and > > > > unfreeze all. Now, another task goes uninterruptible waiting for > > > > disk and situation repeats. Livelock. > > > > > > For how many times would that have to repeat before 30s of timeout expires? > > > > > > Sorry, but I don't buy this argument. :-) > > > > > > > Yes, this might play with races in interresting ways and help fuse, > > > > but we do not want the livelock in the first place. > > > > > > I think that the "livelock" will never happen. > > > > > > Besides, we can add another timeout for breaking the loop from a "locked up" > > > state. > > > > Actually I like this idea. :-) > > > > I have updated the patch to use the additional timeout, please have a look > > (below). > > Yes, this one could actually work... _really_ inefficiently. Not _that_ inefficiently ... > Task here is to sort the tasks, and freeze them in such order that > freezing works, right? Yep, we do not know the dependencies > explicitely... but what you invented is bogosort. Define, please? > Yes, it does increase chance that freezing succeeds, but I do not > think increase of chance is worth having bogosort in tree :-). Well. Do you think it's better to uselessly wait for 20s? Greetings, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth