From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx107.postini.com [74.125.245.107]) by kanga.kvack.org (Postfix) with SMTP id 345CC6B004D for ; Wed, 18 Jan 2012 02:17:04 -0500 (EST) Received: by lagw12 with SMTP id w12so1167327lag.14 for ; Tue, 17 Jan 2012 23:17:02 -0800 (PST) Date: Wed, 18 Jan 2012 09:16:49 +0200 (EET) From: Pekka Enberg Subject: Re: [RFC 1/3] /dev/low_mem_notify In-Reply-To: <20120117232025.GB903@barrios-desktop.redhat.com> Message-ID: References: <1326788038-29141-1-git-send-email-minchan@kernel.org> <1326788038-29141-2-git-send-email-minchan@kernel.org> <4F15A34F.40808@redhat.com> <20120117232025.GB903@barrios-desktop.redhat.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Rik van Riel , linux-mm , LKML , leonid.moiseichuk@nokia.com, kamezawa.hiroyu@jp.fujitsu.com, mel@csn.ul.ie, rientjes@google.com, KOSAKI Motohiro , Johannes Weiner , Marcelo Tosatti , Andrew Morton , Ronen Hod , KOSAKI Motohiro On Wed, 18 Jan 2012, Minchan Kim wrote: > I didn't look into your code(will do) but as I read description, > still I don't convince we need really some process specific threshold like 99% > I think application can know it by polling /proc/meminfo without this mechanism > if they really want. I'm not sure if we need arbitrary threshold either. However, we need to support the following cases: - We're about to swap - We're about to run out of memory - We're about to start OOM killing and I don't think your patch solves that. One possibility is to implement: VMNOTIFY_TYPE_ABOUT_TO_SWAP VMNOTIFY_TYPE_ABOUT_TO_OOM VMNOTIFY_TYPE_ABOUT_TO_OOM_KILL and maybe rip out support for arbitrary thresholds. Does that more reasonable? As for polling /proc/meminfo, I'd much rather deliver stats as part of vmnotify_read() because it's easier to extend the ABI rather than adding new fields to /proc/meminfo. On Wed, 18 Jan 2012, Minchan Kim wrote: > I would like to notify when system has a trobule with memory pressure without > some process specific threshold. Of course, applicatoin can't expect it.(ie, > application can know system memory pressure by /proc/meminfo but it can't know > when swapout really happens). Kernel low mem notify have to give such notification > to user space, I think. It should be simple to add support for VMNOTIFY_TYPE_MEM_PRESSURE that uses your hooks. Pekka -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org