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SubjectRe: [PATCH 2/7] mm: vmscan: Convert lumpy_mode into a bitmask
On Wed, Dec 01, 2010 at 11:56:33AM +0000, Mel Gorman wrote:
> On Wed, Dec 01, 2010 at 12:21:16PM +0100, Johannes Weiner wrote:
> > On Wed, Dec 01, 2010 at 10:50:29AM +0000, Mel Gorman wrote:
> > > 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:
> > > > > + * 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.
> >
> > Sounds like a boolean value to me. And it shows: you never actually
> > check for RECLAIM_MODE_ASYNC in the code, you just always set it to
> > the opposite of RECLAIM_MODE_SYNC - the flag which is actually read.
>
> If you insist, the ASYNC flag can be dropped. I found it easier to flag
> what behaviour was expected than infer it.

It seems to be a matter of taste and nobody else seems to care, so I
am not insisting. Let's just keep it as it is.


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