From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <435883B2.2090400@jp.fujitsu.com> Date: Fri, 21 Oct 2005 14:59:14 +0900 From: KAMEZAWA Hiroyuki MIME-Version: 1.0 Subject: Re: [PATCH 0/4] Swap migration V3: Overview References: <20051020225935.19761.57434.sendpatchset@schroedinger.engr.sgi.com> <20051020160638.58b4d08d.akpm@osdl.org> In-Reply-To: <20051020160638.58b4d08d.akpm@osdl.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: Christoph Lameter , kravetz@us.ibm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, magnus.damm@gmail.com, marcelo.tosatti@cyclades.com List-ID: Andrew Morton wrote: > Christoph Lameter wrote: > >>Page migration is also useful for other purposes: >> >> 1. Memory hotplug. Migrating processes off a memory node that is going >> to be disconnected. >> >> 2. Remapping of bad pages. These could be detected through soft ECC errors >> and other mechanisms. > > > It's only useful for these things if it works with close-to-100% reliability. > > And there are are all sorts of things which will prevent that - mlock, > ongoing direct-io, hugepages, whatever. > In lhms tree, current status is below: (If I'm wrong, plz fix) == For mlock, direct page migration will work fine. try_to_unmap_one() in -mhp tree has an argument *force* and ignore VM_LOCKED, it's for this. For direct-io, we have to wait for completion. The end of I/O is not notified and memory_migrate() is just polling pages. For hugepages, we'll need hugepage demand paging and more work, I think. == When a process migrates to other nodes by hand, it can cooperate with migration subsystem. So we don't have to be afraid of some special using of memory, in many case. I think Christoph's approach will work fine. When it comes to memory-hotplug, arbitrary processes are affected. It's more difficult. We should focus on 'process migraion on demand', in this thread. -- Kame -- 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