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SubjectRe: [PATCH] mm: show total hugetlb memory consumption in /proc/meminfo
On Wed, 15 Nov 2017, Michal Hocko wrote:

> > > > if (!hugepages_supported())
> > > > return;
> > > > seq_printf(m,
> > > > @@ -2987,6 +2989,11 @@ void hugetlb_report_meminfo(struct seq_file *m)
> > > > 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;
> > >
> > > Please keep the total calculation consistent with what we have there
> > > already.
> > >
> >
> > Yeah, and I'm not sure if your comment eludes to this being racy, but it
> > would be better to store the default size for default_hstate during the
> > iteration to total the size for all hstates.
>
> I just meant to have the code consistent. I do not prefer one or other
> option.

It's always nice when HugePages_Total * Hugepagesize cannot become greater
than Hugetlb. Roman, could you factor something like this into your
change accompanied with a documentation upodate as suggested by Dave?

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2975,20 +2975,33 @@ int hugetlb_overcommit_handler(struct ctl_table *table, int write,

void hugetlb_report_meminfo(struct seq_file *m)
{
- struct hstate *h = &default_hstate;
+ struct hstate *h;
+ unsigned long total = 0;
+
if (!hugepages_supported())
return;
- 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) {
+ unsigned long nr_huge_pages = h->nr_huge_pages;
+
+ total += nr_huge_pages <<
+ (huge_page_order(h) + PAGE_SHIFT - 10);
+
+ 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",
+ nr_huge_pages,
+ h->free_huge_pages,
+ h->resv_huge_pages,
+ h->surplus_huge_pages,
+ 1UL << (huge_page_order(h) + PAGE_SHIFT - 10));
+ }
+ }
+ seq_printf(m, "Hugetlb: %5lu kB\n", total);
}

int hugetlb_report_node_meminfo(int nid, char *buf)
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