From mboxrd@z Thu Jan 1 00:00:00 1970 Received: by rn-out-0102.google.com with SMTP id v46so746703rnb for ; Tue, 06 Nov 2007 02:41:21 -0800 (PST) Message-ID: Date: Tue, 6 Nov 2007 11:41:20 +0100 From: "=?ISO-8859-1?Q?Daniel_Sp=E5ng?=" Subject: Re: [RFC Patch] Thrashing notification In-Reply-To: <20071105151723.71b3faaf@bree.surriel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20071105183025.GA4984@dmt> <20071105151723.71b3faaf@bree.surriel.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Rik van Riel Cc: Marcelo Tosatti , linux-mm@kvack.org, drepper@redhat.com, akpm@linux-foundation.org, mbligh@mbligh.org, balbir@linux.vnet.ibm.com, 7eggert@gmx.de List-ID: On 11/5/07, Rik van Riel wrote: > On Mon, 5 Nov 2007 13:30:25 -0500 > Marcelo Tosatti wrote: > > > Hooking into try_to_free_pages() makes the scheme suspectible to > > specifics such as: > > The specific of where the hook is can be changed. I am sure the > two of you can come up with the best way to do things. Just keep > shooting holes in each other's ideas until one idea remains which > neither of you can find a problem with[1] :) > > > Remember that notifications are sent to applications which can allocate > > globally... > > This is the bigger problem with the sysfs code: every task that > watches the sysfs node will get woken up. That could be a big > problem when there are hundreds of processes watching that file. > > Marcelo's code, which only wakes up one task at a time, has the > potential to work much better. That code can also be enhanced > to wake up tasks that use a lot of memory on the specific NUMA > node that has a memory shortage. > > [1] Yes, that is how I usually come up with VM ideas :) I have actually no problem at all using a device to get the message to userspace. My patch was more like a demonstration of when to trigger the notification. I still (obviously) think that we need a notification for systems without swap too. A concern, or feature =), with the notify-on-swap method is that with responsive user applications, it will never use swap at all. There are for sure systems where this behavior is desirable, but for example desktop systems, the memory occupied by inactive processes might be better used by active ones. I think there is a need for both notifications, first a notification when we are about to swap and then one to trigger when the total free vm is low or when the system is thrashing, preferable using the same notification method. -- 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/ . Don't email: email@kvack.org