From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id 528216B01E3 for ; Tue, 13 Apr 2010 09:46:16 -0400 (EDT) Date: Tue, 13 Apr 2010 15:44:56 +0200 From: Andrea Arcangeli Subject: Re: [PATCH 00 of 41] Transparent Hugepage Support #17 Message-ID: <20100413134456.GQ5583@random.random> References: <20100412071525.GR5683@laptop> <4BC2CF8C.5090108@redhat.com> <20100412082844.GU5683@laptop> <4BC2E1D6.9040702@redhat.com> <20100412092615.GY5683@laptop> <4BC2EFBA.5080404@redhat.com> <20100412203829.871f1dee.akpm@linux-foundation.org> <20100413161802.498336ca@notabene.brown> <20100413133153.GO5583@random.random> <20100413134035.GY25756@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100413134035.GY25756@csn.ul.ie> Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Neil Brown , Andrew Morton , Avi Kivity , Nick Piggin , Ingo Molnar , Mike Galbraith , Jason Garrett-Glaser , Linus Torvalds , Pekka Enberg , linux-mm@kvack.org, Marcelo Tosatti , Adam Litke , Izik Eidus , Hugh Dickins , Rik van Riel , Dave Hansen , Benjamin Herrenschmidt , Mike Travis , KAMEZAWA Hiroyuki , Christoph Lameter , Chris Wright , bpicco@redhat.com, KOSAKI Motohiro , Balbir Singh , Arnd Bergmann , "Michael S. Tsirkin" , Peter Zijlstra , Johannes Weiner , Daisuke Nishimura List-ID: On Tue, Apr 13, 2010 at 02:40:35PM +0100, Mel Gorman wrote: > On Tue, Apr 13, 2010 at 03:31:54PM +0200, Andrea Arcangeli wrote: > > Hi Neil! > > > > On Tue, Apr 13, 2010 at 04:18:02PM +1000, Neil Brown wrote: > > > Actually I don't think that would be hard at all. > > > ->lookup can return a different dentry than the one passed in, usually using > > > d_splice_alias to find it. > > > So when you create an inode for a directory, create an anonymous dentry, > > > attach it via i_dentry, and it should "just work". > > > That is assuming this is still a "problem" that needs to be "fixed". > > > > I'm not sure if changing the slab object will make a whole lot of > > difference, because antifrag will threat all unmovable stuff the > > same. > > Anti-frag considers reclaimable slab caches to be different to unmovable > allocations. Slabs with the SLAB_RECLAIM_ACCOUNT use the __GFP_RECLAIMABLE > flag. It was to keep truly unmovable allocations in the same 2M pages where > possible. As long as we keep the reclaimable separated from the "movable" that's fine. > It also means that even with large bursts of kernel allocations due to big > filesystem loads, the system will still get some of those 2M blocks back > eventually when slab eventually ages and shrinks. Only if the file isn't open... it's not really certain it's reclaimable. > You can use /proc/pagetypeinfo to get a count of the 2M blocks of each > type for different types of workloads to see what the scenarios look like > from an anti-frag and compaction perspective but very loosly speaking, > with compaction applied, you'd expect to be able to covert all "Movable" > blocks to huge pages by either compacting or paging. You'll get some of the > "Reclaimable" blocks if slab is shrunk enough the unmovable blocks depends > on how many of the allocations are due to pagetables. Awesome statistic! -- 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