Re: [PATCH] mm: make transparent hugepage size public

[Hugh Dickins <hughd@google.com>]

On Tue, 6 Dec 2016, Dave Hansen wrote:
> On 12/06/2016 09:19 AM, Kirill A. Shutemov wrote:
> >>> > > We have in /proc/meminfo
> >>> > > 
> >>> > > Hugepagesize:       2048 kB
> >>> > > 
> >>> > > Does it makes it easy for application to find THP page size also there ?
> >> > 
> >> > Nope.  That's the default hugetlbfs page size.  Even on x86, that can be
> >> > changed and _could_ be 1G.  If hugetlbfs is configured out, you also
> >> > won't get this in meminfo.
> > I think Aneesh propose to add one more line into the file.
> 
> Ahhh, ok...
> 
> Personally, I think Hugh did the right things.  There's no reason to
> waste cycles sticking a number in meminfo that never changes.

Thanks, yes, that was my feeling: I prefer not to clutter /proc/meminfo
with constants - especially not a unit, or granularity, as this is
(too late to stop Hugepagesize of course, but I wish it weren't there,
and those HugePages_ numbers in kB).

On top of that, /proc/meminfo is the mm admin's "front page", whereas
this is a low-level detail: it somewhat goes against our claim of
"transparent" hugepages to post it up there, even though a few tests
etc may find the value useful: I'd rather bury it among the tunables.
(My guess is that Andrea felt rather the same, in choosing not to
publish it six years ago.)

But of course, that's just my/our opinion: any strong preferences?

Hugh

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