From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 25 May 2006 18:23:18 -0700 (PDT) From: Christoph Lameter Subject: Re: Add /proc/sys/vm/drop_node_caches In-Reply-To: <20060525173139.036356bf.akpm@osdl.org> Message-ID: References: <20060525170509.331aaf2d.akpm@osdl.org> <20060525173139.036356bf.akpm@osdl.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: linux-mm@kvack.org List-ID: On Thu, 25 May 2006, Andrew Morton wrote: > Christoph Lameter wrote: > > > > On Thu, 25 May 2006, Andrew Morton wrote: > > > > > If we're talking about some formal, supported access to the kernel's NUMA > > > facilities then poking away at /proc doesn't seem a particularly good way > > > of doing it. The application _should_ be able to set its memory policy to > > > point at that node and get all the old caches evicted automatically. If > > > that doesn't work, what's wrong? > > > > zone_reclaim does exactly that for an application. So that case is > > covered. > > > > However, there are situations in which someone wants to insure that there > > is no pagecache on some nodes (testing and some special apps). > > What situations? Why doesn't zone_reclaim suit in those cases? We already have your hack for all nodes. Most of our systems are segmented into subsets of nodes so there is a desire to have that same hack for some nodes. The same arguments that justified the introduction of drop_cache also justify drop_node_caches. Tests will produce more consistent results and applications can be sure to start with all of memory free. Its only active for CONFIG_NUMA. I can check and see if I find more supporting arguments tomorrow when I have a chance to talk with those who want this feature. -- 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