Re: [PATCH] Add __GFP_MOVABLE for callers to flag allocations that may be migrated

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]


On (05/12/06 12:01), Christoph Lameter didst pronounce:
> On Tue, 5 Dec 2006, Andrew Morton wrote:
> > > We always run reclaim against the whole zone not against parts. Why 
> > > would we start running reclaim against a portion of a zone?
> > 
> > Oh for gawd's sake.
> Yes indeed. Another failure to answer a simple question.

There are times you want to reclaim just part of a zone - specifically
satisfying a high-order allocations. See sitations 1 and 2 from elsewhere
in this thread. On a similar vein, there will be times when you want to
migrate a PFN range for similar reasons.

> > If you want to allocate a page from within the first 1/4 of a zone, and if
> > all those pages are in use for something else then you'll need to run
> > reclaim against the first 1/4 of that zone.  Or fail the allocation.  Or
> > run reclaim against the entire zone.  The second two options are
> > self-evidently dumb.
> Why would one want to allocate from the 1/4th of a zone? (Are we still 
> discussing Mel's antifrag scheme or what is this about?)

Because you wanted contiguous blocks of pages.  This is related to anti-frag
because with anti-frag, reclaiming memory or migration memory will free up
contiguous blocks. Without it, you're probably wasting your time.

Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at
Please read the FAQ at

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux