lkml.org 
[lkml]   [2009]   [Nov]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCHv2 2/5] vmscan: Kill hibernation specific reclaim logic and unify it
Date
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


\
 
 \ /
  Last update: 2009-11-03 23:01    [from the cache]
©2003-2011 Jasper Spaans