From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <436888E7.1060609@yahoo.com.au> Date: Wed, 02 Nov 2005 20:37:43 +1100 From: Nick Piggin MIME-Version: 1.0 Subject: Re: [Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19 References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Gerrit Huizenga Cc: Ingo Molnar , Kamezawa Hiroyuki , Dave Hansen , Mel Gorman , "Martin J. Bligh" , Andrew Morton , kravetz@us.ibm.com, linux-mm , Linux Kernel Mailing List , lhms List-ID: Gerrit Huizenga wrote: > On Wed, 02 Nov 2005 19:50:15 +1100, Nick Piggin wrote: >>Isn't the solution for your hypervisor problem to dish out pages of >>the same size that are used by the virtual machines. Doesn't this >>provide you with a nice, 100% solution that doesn't add complexity >>where it isn't needed? > > > So do you see the problem with fragementation if the hypervisor is > handing out, say, 1 MB pages? Or, more likely, something like 64 MB > pages? What are the chances that an entire 64 MB page can be freed > on a large system that has been up a while? > I see the problem, but if you want to be able to shrink memory to a given size, then you must either introduce a hard limit somewhere, or have the hypervisor hand out guest sized pages. Use zones, or Xen? > And, if you create zones, you run into all of the zone rebalancing > problems of ZONE_DMA, ZONE_NORMAL, ZONE_HIGHMEM. In that case, on > any long running system, ZONE_HOTPLUGGABLE has been overwhelmed with > random allocations, making almost none of it available. > If there are zone rebalancing problems[*], then it would be great to have more users of zones because then they will be more likely to get fixed. [*] and there are, sadly enough - see the recent patches I posted to lkml for example. But I'm fairly confident that once the particularly silly ones have been fixed, zone balancing will no longer be a derogatory term as has been thrown around (maybe rightly) in this thread! -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com -- 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