Messages in this thread |  | | | From | "Rafael J. Wysocki" <> | | Subject | Re: [PATCHv2 2/5] vmscan: Kill hibernation specific reclaim logic and unify it | | Date | Tue, 3 Nov 2009 23:00:14 +0100 |
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On Tuesday 03 November 2009, Nigel Cunningham wrote: > Hi Rafael. > > Rafael J. Wysocki wrote: > > On Monday 02 November 2009, Nigel Cunningham wrote: > >> Hi. > > > > Hi, > > > >> KOSAKI Motohiro wrote: > >>>> I haven't given much thought to numa awareness in hibernate code, but I > >>>> can say that the shrink_all_memory interface is woefully inadequate as > >>>> far as zone awareness goes. Since lowmem needs to be atomically restored > >>>> before we can restore highmem, we really need to be able to ask for a > >>>> particular number of pages of a particular zone type to be freed. > >>> Honestly, I am not suspend/hibernation expert. Can I ask why caller need to know > >>> per-zone number of freed pages information? if hibernation don't need highmem. > >>> following incremental patch prevent highmem reclaim perfectly. Is it enough? > >> (Disclaimer: I don't think about highmem a lot any more, and might have > >> forgotten some of the details, or swsusp's algorithms might have > >> changed. Rafael might need to correct some of this...) > >> > >> Imagine that you have a system with 1000 pages of lowmem and 5000 pages > >> of highmem. Of these, 950 lowmem pages are in use and 500 highmem pages > >> are in use. > >> > >> In order to to be able to save an image, we need to be able to do an > >> atomic copy of those lowmem pages. > >> > >> You might think that we could just copy everything into the spare > >> highmem pages, but we can't because mapping and unmapping the highmem > >> pages as we copy the data will leave us with an inconsistent copy. > > > > This isn't the case any more for the mainline hibernate code. We use highmem > > for storing image data as well as lowmem. > > Highmem for storing copies of lowmem pages?
It is possible in theory, but I don't think it happens in practice given the way in which the memory is freed. Still copy_data_page() takes this possibility into account.
Thanks, Rafael
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