From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx192.postini.com [74.125.245.192]) by kanga.kvack.org (Postfix) with SMTP id 877E36B0032 for ; Thu, 15 Aug 2013 09:56:32 -0400 (EDT) Date: Thu, 15 Aug 2013 14:56:27 +0100 From: Mel Gorman Subject: Re: kswapd skips compaction if reclaim order drops to zero? Message-ID: <20130815135627.GX2296@suse.de> References: <20130815104727.GT2296@suse.de> <20130815134139.GC8437@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20130815134139.GC8437@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Hillf Danton , LKML , Linux-MM On Thu, Aug 15, 2013 at 10:41:39PM +0900, Minchan Kim wrote: > Hey Mel, > > On Thu, Aug 15, 2013 at 11:47:27AM +0100, Mel Gorman wrote: > > On Thu, Aug 15, 2013 at 06:02:53PM +0800, Hillf Danton wrote: > > > If the allocation order is not high, direct compaction does nothing. > > > Can we skip compaction here if order drops to zero? > > > > > > > If the allocation order is not high then > > > > pgdat_needs_compaction == (order > 0) == false == no calling compact_pdatt > > > > In the case where order is reset to 0 due to fragmentation then it does > > call compact_pgdat but it does no work due to the cc->order check in > > __compact_pgdat. > > > > I am looking at mmotm-2013-08-07-16-55 but couldn't find cc->order > check right before compact_zone in __comact_pgdat. > Could you pinpoint code piece? > Thanks, I screwed up as that check happens too late. However, it still ends up not mattering because it does this compact_pgdat -> __compact_pgdat -> compact_zone -> compaction_suitable For order == 0, compaction_suitable will return either COMPACT_SKIPPED (if the watermarks are not met) and COMPACT_PARTIAL otherwise. Either way, compaction doesn't run. -- Mel Gorman SUSE Labs -- 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