From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 10 Jul 2007 18:54:49 +0900 From: Yasunori Goto Subject: Re: zone movable patches comments In-Reply-To: <46934F9C.9060201@shadowen.org> References: <46933BD7.2020200@yahoo.com.au> <46934F9C.9060201@shadowen.org> Message-Id: <20070710182944.83D7.Y-GOTO@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Andy Whitcroft Cc: Nick Piggin , Mel Gorman , Linux Memory Management , Andrew Morton , kamezawa.hiroyu@jp.fujitsu.com List-ID: > > No I really don't see why kernelcore=toosmall is any better than > > movable_mem=toobig. And why do you think the admin knows how much > > memory is enough to run the kernel, or why should that be the same > > between different sized machines? If you have a huge machine, you > > need much more addressable kernel memory for the mem_map array > > before you even think about anything else. > > > > Actually, it is more likely that the admin knows exactly how much > > memory they need to reserve (eg. for their database's shared > > memory segment or to hot unplug or whatever), and in that case > > it is much better to be able to specify movable_mem= and just be > > given exactly what you asked for and the kernel can be given the > > rest. If hot-unplug is invoked after bootup, then movable_mem will be useful to specify removable memory size. It is true. However, if hot-add is invoked at first after bootup, movable_mem is not so useful. I think admin expects hot-add memory will be removable zone in many case, because he wish the memory for his application rather than for kernel. But, movable mem can't specify size of hot-add memory in the future. I suppose "kernelcore" is desirable for its case. > > If somebody is playing with this parameter, they definitely know > > what they are doing and they are not just blindly throwing it out > > over their cluster because it might be a good idea. > > It feels very much that there are two usage models. Those who know how > much "kernel" memory works for them and want whatever is left usable for > their small/huge page workloads, and those who know how much they need > for their DB and are happy for the system to have the rest. Both seem > like valid use cases, both would have the same underlying implementation > a sized ZONE_MOVABLE. > > How about we have two kernel options "kernelcore=" and "movable=" which > would both size ZONE_MOVABLE. Both would be the minimum sizes, so the > effective differences would be the rounding to whole pageblocks. I would like to vote it due to above mentioned. :-) Bye. -- Yasunori Goto -- 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