From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 1 Nov 2006 22:13:59 +0000 (GMT) From: Mel Gorman Subject: Re: Page allocator: Single Zone optimizations In-Reply-To: Message-ID: References: <20061027190452.6ff86cae.akpm@osdl.org> <20061027192429.42bb4be4.akpm@osdl.org> <20061027214324.4f80e992.akpm@osdl.org> <20061028180402.7c3e6ad8.akpm@osdl.org> <4544914F.3000502@yahoo.com.au> <20061101182605.GC27386@skynet.ie> <20061101123451.3fd6cfa4.akpm@osdl.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Andrew Morton , Mel Gorman , Nick Piggin , KAMEZAWA Hiroyuki , linux-mm@kvack.org List-ID: On Wed, 1 Nov 2006, Christoph Lameter wrote: > On Wed, 1 Nov 2006, Andrew Morton wrote: > >> And hot-unplug isn't actually the interesting application. Modern Intel >> memory controllers apparently have (or will have) the ability to power down >> DIMMs. > > Plus one would want to be able to move memory out of an area where we may > have a bad DIMM. If we monitor soft ECC failures then we could also > judge a DIMM to be bad if we have a too high soft failure rate. > For this, it'd be desirable to be able to marge a range of pages as unusable. In the anti-frag patches I posted, I included a mechanism for having flags that affected a whole block of pages. One intent in the future was to be able to mark a whole block of pages as getting reclaimed for the allocation of superpages. The same mechanism could be used to mark pages as being offlined so you could mark a DIMM as offlined and start reclaiming in there knowing it can be unplugged some time in the future. > If there is a hard failure and we can recover (page cache page f.e.) > then we could preemptively disable the complete DIMM. > > I still think that we need to generalize the approach to be > able to cover as much memory as possible. Remapping can solve some of the > issues, for others we could add additional ways to make things movable. > F.e. one could make page table pages movable by adding a back pointer to > the mm, reclaimable slab pages by adding a move function, driver > allocations could have a backpointer to the driver that would be able to > move its memory. I got the impression that we wouldn't be allowed to introduce such a mechanism because driver writers would get it wrong. It was why proper defragmentation was never really implemented. > Hmm.... Maybe generally a way to provide a > function to move data in the page struct for kernel allocations? > As devices are able to get physical addresses which then get pinned for IO, it gets messy. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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