Messages in this thread | | | Date | Wed, 07 Apr 2004 15:33:38 -0700 | From | "Martin J. Bligh" <> | Subject | Re: [Lhms-devel] Re: [patch 0/3] memory hotplug prototype |
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--On Wednesday, April 07, 2004 11:59:53 -0700 Mike Kravetz <kravetz@us.ibm.com> wrote:
> On Wed, Apr 07, 2004 at 11:12:55AM -0700, Martin J. Bligh wrote: >> > This is an updated version of memory hotplug prototype patch, which I >> > have posted here several times. >> >> I really, really suggest you take a look at Dave McCracken's work, which >> he posted as "Basic nonlinear for x86" recently. It's going to be much >> much easier to use this abstraction than creating 1000s of zones ... >> > > I agree. However, one could argue that taking a zone offline is 'easier' > than taking a 'section' offline: at least right now. Note that I said > easier NOT better. Currently a section represents a subset of one or more > zones. Ideally, these sections represent units that can be added or > removed. IIRC these sections only define a range of physical memory. > To determine if it is possible to take a section offline, one needs to > dig into the zone(s) that the section may be associated with. We'll > have to do things like: > - Stop allocations of pages associated with the section. > - Grab all 'free pages' associated with the section. > - Try to reclaim/free all pages associated with the section. > - Work on this until all pages in the section are not in use (or free). > - OR give up if we know we will not succeed. > > My claim of zones being easier to work with today is due to the > fact that zones contain much of the data/infrastructure to make > these types of operations easy. For example, in IWAMOTO's code a > node/zone can be take offline when 'z->present_pages == z->free_pages'.
I really think the level of difference in difficultly here is trivial. The hard bit is freeing the pages, not measuring them. I would suspect altering the swap path to just not "free" the pages, but put them into a pool for hotplug is fairly easy.
M.
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