On Tue, 7 Sep 2010 10:46:35 +0200 Andi Kleen <andi@xxxxxxxxxxxxxx> wrote: > On Tue, 7 Sep 2010 17:25:59 +0900 > KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > > On Tue, 07 Sep 2010 09:29:21 +0200 > > Andi Kleen <andi@xxxxxxxxxxxxxx> wrote: > > > > > KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> writes: > > > > > > > This is a page allcoator based on memory migration/hotplug code. > > > > passed some small tests, and maybe easier to read than previous > > > > one. > > > > > > Maybe I'm missing context here, but what is the use case for this? > > > > > > > I hear some drivers want to allocate xxMB of continuous area.(camera?) > > Maybe embeded guys can answer the question. > > Ok what I wanted to say -- assuming you can make this work > nicely, and the delays (swap storms?) likely caused by this are not > too severe, it would be interesting for improving the 1GB pages on x86. > Oh, I didn't consider that. Hmm. If x86 really wants to support 1GB page, MAX_ORDER should be raised. (I'm sorry if it was already disccused.) > This would be a major use case and probably be enough > to keep the code around. > > But it depends on how well it works. > Sure. > e.g. when the zone is already fully filled how long > does the allocation of 1GB take? > Maybe not very quick, even slow. > How about when parallel programs are allocating/freeing > in it too? > This code doesn't assume that. I wonder I should add mutex because this code generates IPI for draining some per-cpu lists. I think 1GB pages should be preallocated as current hugepage does. > What's the worst case delay under stress? > memory offline itself is robust against stress because it make pageblock ISOLATED. But memory allocation of 1GB is problem. I have an idea (see below). > Does it cause swap storms? > Maybe same as allocating 1GB of memory when memory is full. It's LRU matter. > One issue is also that it would be good to be able to decide > in advance if the OOM killer is likely triggered (and if yes > reject the allocation in the first place). > Checking the amount of memory and swap before starts ? It sounds nice. I'd like to add something. Or changing my patche's logic as.. 1. allocates required migration target pages (of 1GB) 2. start migration to allocated pages. 3. create a big page. Then, we can use some GFP_XXXX at (1) and can do some tuning as usual vm codes. Thanks, -Kame -- 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>