On Wed, Dec 01, 2010 at 11:27:32AM +0100, Johannes Weiner wrote:
> On Mon, Nov 22, 2010 at 03:43:50PM +0000, Mel Gorman wrote:
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -51,11 +51,20 @@
> > #define CREATE_TRACE_POINTS
> > #include <trace/events/vmscan.h>
> >
> > -enum lumpy_mode {
> > - LUMPY_MODE_NONE,
> > - LUMPY_MODE_ASYNC,
> > - LUMPY_MODE_SYNC,
> > -};
> > +/*
> > + * lumpy_mode determines how the inactive list is shrunk
> > + * LUMPY_MODE_SINGLE: Reclaim only order-0 pages
> > + * LUMPY_MODE_ASYNC: Do not block
> > + * LUMPY_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback
> > + * LUMPY_MODE_CONTIGRECLAIM: For high-order allocations, take a reference
> > + * page from the LRU and reclaim all pages within a
> > + * naturally aligned range
>
> I find those names terribly undescriptive. It also strikes me as an
> odd set of flags. Can't this be represented with less?
>
> LUMPY_MODE_ENABLED
> LUMPY_MODE_SYNC
>
> or, after the rename,
>
> RECLAIM_MODE_HIGHER = 1
> RECLAIM_MODE_SYNC = 2
> RECLAIM_MODE_LUMPY = 4
>
My problem with that is you have to infer what the behaviour is from what the
flags "are not" as opposed to what they are. For example, !LUMPY_MODE_SYNC
implies LUMPY_MODE_ASYNC instead of specifying LUMPY_MODE_ASYNC. It also
looks very odd when trying to distinguish between order-0 standard reclaim,
lumpy reclaim and reclaim/compaction.
> where compaction mode is default if RECLAIM_MODE_HIGHER, and
> RECLAIM_MODE_LUMPY will go away eventually.
>
> Also, if you have a flag name for 'reclaim with extra efforts for
> higher order pages' that is better than RECLAIM_MODE_HIGHER... ;)
>
> > +typedef unsigned __bitwise__ lumpy_mode;
>
> lumpy_mode_t / reclaim_mode_t?
>
It can't hurt!
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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