Re: [RFC PATCH 6/8] mm: Demarcate and maintain pageblocks in region-orderin the zones' freelists

[Dave Hansen]

On 11/06/2012 11:53 AM, Srivatsa S. Bhat wrote:
> This is the main change - we keep the pageblocks in region-sorted order,
> where pageblocks belonging to region-0 come first, followed by those belonging
> to region-1 and so on. But the pageblocks within a given region need *not* be
> sorted, since we need them to be only region-sorted and not fully
> address-sorted.
> 
> This sorting is performed when adding pages back to the freelists, thus
> avoiding any region-related overhead in the critical page allocation
> paths.

It's probably _better_ to do it at free time than alloc, but it's still
pretty bad to be doing a linear walk over a potentially 256-entry array
holding the zone lock.  The overhead is going to show up somewhere.  How
does this do with a kernel compile?  Looks like exit() when a process
has a bunch of memory might get painful.

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