On Tue, Sep 07, 2010 at 05:47:43PM +0900, KAMEZAWA Hiroyuki wrote: > On Tue, 7 Sep 2010 01:37:27 -0700 > Minchan Kim <minchan.kim@xxxxxxxxx> wrote: > > > Nice cleanup. > > There are some comments in below. > > > > On Mon, Sep 6, 2010 at 7:45 PM, KAMEZAWA Hiroyuki > > <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > > > > > This is a page allcoator based on memory migration/hotplug code. > > > passed some small tests, and maybe easier to read than previous one. > > > > > > == > > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > > > > > > This patch as a memory allocator for contiguous memory larger than MAX_ORDER. > > > > > > ??alloc_contig_pages(hint, size, node); > > > > I have thought this patch is to be good for dumb device drivers which > > want big contiguous > > memory. So if some device driver want big memory and they can tolerate > > latency or fail, > > this is good solution, I think. > > And some device driver can't tolerate fail, they have to use MOVABLE zone. > > > > For it, I hope we have a option like ALLOC_FIXED(like MAP_FIXED). > > That's because embedded people wanted to aware BANK of memory. > > So if they get free page which they don't want, it can be pointless. > > > Okay. > > > > In addition, I hope it can support CROSS_ZONE migration mode. > > Most of small system can't support swap system. So if we can't migrate > > anon pages into other zones, external fragment problem still happens. > > > Now, this code migrates pages to somewhere, including crossing zone, node etc.. > (because it just use GFP_HIGHUSER_MOVABLE) > > > I think reclaim(ex, discard file-backed pages) can become one option to prevent > > the problem. But it's more cost so we can support it by calling mode. > > (But it could be trivial since caller should know this function is very cost) > > > > > ex) alloc_contig_pages(hint, size, node, ALLOC_FIXED|ALLOC_RECLAIM); > > > > This migration's page allocation code will cause memory reclaim and > kswapd wakeup if memory is in short. But hmm, there are no codes as Yes. But it's useless. That's because it's not a zone/node we want to reclaim. The zone we want to reclaim is not alloc failed zone but the zone which include alloc_contig_pages's hint address. > > reclaim_memory_within(start, end). > > But I guess if there are LRU pages within the range which cannot be migrated, > they can't be dropped. In another consideration, > > shrink_slab_within(start, end) > will be able to make success-rate better. (and this is good for memory hotplug, too) And it can help normal external memory fragement, too. > > I'll start from adding ALLOC_FIXED. I am looking forward to seeing your next version. :) Thanks, Kame. -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>