From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 27 Oct 2006 19:24:29 -0700 From: Andrew Morton Subject: Re: Page allocator: Single Zone optimizations Message-Id: <20061027192429.42bb4be4.akpm@osdl.org> In-Reply-To: References: <20061017102737.14524481.kamezawa.hiroyu@jp.fujitsu.com> <45347288.6040808@yahoo.com.au> <45360CD7.6060202@yahoo.com.au> <20061018123840.a67e6a44.akpm@osdl.org> <20061026150938.bdf9d812.akpm@osdl.org> <20061027190452.6ff86cae.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Nick Piggin , KAMEZAWA Hiroyuki , linux-mm@kvack.org List-ID: On Fri, 27 Oct 2006 19:12:16 -0700 (PDT) Christoph Lameter wrote: > On Fri, 27 Oct 2006, Andrew Morton wrote: > > > On Fri, 27 Oct 2006 18:00:42 -0700 (PDT) > > Christoph Lameter wrote: > > > > > But I cannot find any justification in my contexts to complete work on > > > this functionality because plainly all the hardware that I use does not > > > have problem laden DMA controllers and works just fine with a single > > > zone. > > > > How about memory hot-unplug? > > Cannot figure out how that relates to what I said above. We need some way of preventing unreclaimable kernel memory allocations from using certain physical pages. That means zones. > Memory hot unplug > seems to have been dropped in favor of baloons. Has it? I don't recall seeing a vague proposal, let alone an implementation? > > The only feasible way we're going to implement that is to support it on > > user allocations only. IOW: for all those allocations which were performed > > with __GFP_HIGHMEM. > > The alloc_page_range() functionality was intended for device drivers and > other ZONE_DMA users. I am not sure what the point is of user space > having the ability to allocate memory in specific physical memory areas. Userspace allocations are reclaimable: pagecache, anonymous memory. These happen to be allocated with __GFP_HIGHMEM set. So right now __GFP_HIGHMEM is an excellent hint telling the page allocator that it is safe to satisfy this request from removeable memory. -- 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