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SubjectRe: [PATCH v2] mm: show total hugetlb memory consumption in /proc/meminfo
On Tue, 21 Nov 2017 15:15:55 +0000 Roman Gushchin <guro@fb.com> wrote:

> > > +
> > > + for_each_hstate(h) {
> > > + unsigned long count = h->nr_huge_pages;
> > > +
> > > + total += (PAGE_SIZE << huge_page_order(h)) * count;
> > > +
> > > + if (h == &default_hstate)
> >
> > I'm not understanding this test. Are we assuming that default_hstate
> > always refers to the highest-index hstate? If so why, and is that
> > valid?
>
> As Mike and Michal pointed, default_hstate is defined as
> #define default_hstate (hstates[default_hstate_idx]),
> where default_hstate_idx can be altered by a boot argument.
>
> We're iterating over all states to calculate total and also
> print some additional info for the default size. Having a single
> loop guarantees consistency of these numbers.
>

OK, I misread the handling of `count' -> HugePages_Total.

It seems unnecessarily obscure?

for_each_hstate(h) {
unsigned long count = h->nr_huge_pages;

total += (PAGE_SIZE << huge_page_order(h)) * count;

if (h == &default_hstate)
seq_printf(m,
"HugePages_Total: %5lu\n"
"HugePages_Free: %5lu\n"
"HugePages_Rsvd: %5lu\n"
"HugePages_Surp: %5lu\n"
"Hugepagesize: %8lu kB\n",
count,
h->free_huge_pages,
h->resv_huge_pages,
h->surplus_huge_pages,
(PAGE_SIZE << huge_page_order(h)) / 1024);
}

seq_printf(m, "Hugetlb: %8lu kB\n", total / 1024);


Why not

seq_printf(m,
"HugePages_Total: %5lu\n"
"HugePages_Free: %5lu\n"
"HugePages_Rsvd: %5lu\n"
"HugePages_Surp: %5lu\n"
"Hugepagesize: %8lu kB\n",
h->nr_huge_pages,
h->free_huge_pages,
h->resv_huge_pages,
h->surplus_huge_pages,
1UL << (huge_page_order(h) + PAGE_SHIFT - 10));

for_each_hstate(h)
total += (PAGE_SIZE << huge_page_order(h)) * h->nr_huge_pages;
seq_printf(m, "Hugetlb: %8lu kB\n", total / 1024);

?

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