Re: [PATCH] proc: task_mmu: show page size in /proc/<pid>/numa_maps

[Rafael Aquini <aquini@redhat.com>]

On Mon, Dec 22, 2014 at 09:10:34AM -0800, Dave Hansen wrote:
> On 12/21/2014 02:28 PM, Rafael Aquini wrote:
> >>> > > I'm fine either way, it makes the change even simpler. Also, if we
> >>> > > decide to get rid of page_size != PAGE_SIZE condition I believe we can 
> >>> > > also get rid of that "huge" hint being conditionally printed out too.
> >> > 
> >> > That would break existing users of the "huge" flag.  That makes it out
> >> > of the question, right?
> >> >
> > Yeah, but it sort of follows the same complaint Johannes did for the 
> > conditional page size printouts. If we start to print out page size
> > deliberately for each map regardless their backing pages being PAGE_SIZE 
> > long or bigger, I don't see much point on keep conditionally printing out 
> > the 'huge' hint out.
> 
> Because existing userspace might be relying on it.  If we take the
> 'huge' hint out, userspace will break.
> 
> > As I said before, I'm fine either way though I think
> > we can keep the current behaviour, and just disambiguate page sizes !=
> > PAGE_SIZE as in the current proposal.
> 
> Unless we somehow have a (really good) handle on how many apps out there
> are reading and using 'huge', I think we have to keep the existing behavior.
>
Right. I definitely don't have anything better than what I already
presented which seems beaten by your argument, already. 
Remaining question here is: should we print out 'pagesize' deliberately 
or conditionally, only to disambiguate cases where page_size != PAGE_SIZE?

Have a very nice holidays folks!
-- Rafael

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