From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 7 Jun 2001 16:40:28 -0300 (BRT) From: Marcelo Tosatti Subject: Re: Please test: workaround to help swapoff behaviour In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Bulent Abali Cc: Mike Galbraith , "Eric W. Biederman" , Derek Glidden , lkml , linux-mm@kvack.org List-ID: On Thu, 7 Jun 2001, Bulent Abali wrote: > > I tested your patch against 2.4.5. It works. No more lockups. Without > the > patch it took 14 minutes 51 seconds to complete swapoff (this is to recover > 1.5GB of > swap space). During this time the system was frozen. No keyboard, no > screen, etc. Practically locked-up. > > With the patch there are no more lockups. Swapoff kept running in the > background. > This is a winner. > > But here is the caveat: swapoff keeps burning 100% of the cycles until it > completes. Yup. Wait a while until the dead swap cache issue is sorted out. When that finally happens, the time spent in swapoff will probably be "acceptable". > This is not going to be a big deal during shutdowns. Only when you enter > swapoff from > the command line it is going to be a problem. > > I looked at try_to_unuse in swapfile.c. I believe that the algorithm is > broken. Yes. > For each and every swap entry it is walking the entire process list > (for_each_task(p)). It is also grabbing a whole bunch of locks > for each swap entry. It might be worthwhile processing swap entries in > batches instead of one entry at a time. The real fix is to make the processing the other way around --- go looking into the pte's and from there do the swapins. Don't have the time to do everything, though. :) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/