From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id 01DA96B004A for ; Wed, 29 Sep 2010 10:54:56 -0400 (EDT) Date: Wed, 29 Sep 2010 09:54:54 -0500 (CDT) From: Christoph Lameter Subject: Re: zone state overhead In-Reply-To: <20100929144556.GD14204@csn.ul.ie> Message-ID: References: <20100928050801.GA29021@sli10-conroe.sh.intel.com> <20100928133059.GL8187@csn.ul.ie> <20100929100307.GA14204@csn.ul.ie> <20100929141730.GB14204@csn.ul.ie> <20100929144159.GC14204@csn.ul.ie> <20100929144556.GD14204@csn.ul.ie> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: David Rientjes , Shaohua Li , linux-mm@kvack.org List-ID: On Wed, 29 Sep 2010, Mel Gorman wrote: > I should be clearer here. Initially, I'm thinking the consequences of moving > it are not terrible bad so I'm wondering if you see some problem I have not > thought of. If the threshold value is sharing the cache line with watermark > or lowmem_reserve, then it should still have the same hotness in the path > we really care about (zone_watermark_ok for example) without necessarily > needing to be part of the per-cpu structure. The real badness would be if an > additional cache line was required due to the move but I don't think this is > the case (but I didn't double check with pahole or the back of an envelope > either). The line will be dirtied and cause a bounce when kswapd wakes or > goes to sleep but this should not be a severe problem. The critical paths for vm statistics are __inc_zone_state() and __dec_zone_state(). Those are sprinkled all over. -- 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