Re: [PATCH v2 2/2] mm: hugetlb: add VmHugetlbRSS: field in /proc/pid/status

Andrew Morton
2015-08-07T22:55:39Z

On Fri, 7 Aug 2015 07:24:50 +0000 Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> wrote:

> Currently there's no easy way to get per-process usage of hugetlb pages, which
> is inconvenient because applications which use hugetlb typically want to control
> their processes on the basis of how much memory (including hugetlb) they use.
> So this patch simply provides easy access to the info via /proc/pid/status.
>
> This patch shouldn't change the OOM behavior (so hugetlb usage is ignored as
> is now,) which I guess is fine until we have some strong reason to do it.
>

A procfs change triggers a documentation change. Always, please.
Documentation/filesystems/proc.txt is the place.

>
> ...
>
> @@ -504,6 +519,9 @@ static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
> {
> return &mm->page_table_lock;
> }
> +
> +#define get_hugetlb_rss(mm) 0
> +#define mod_hugetlb_rss(mm, value) do {} while (0)

I don't think these have to be macros? inline functions are nicer in
several ways: more readable, more likely to be documented, can prevent
unused variable warnings.

> #endif /* CONFIG_HUGETLB_PAGE */
>
> static inline spinlock_t *huge_pte_lock(struct hstate *h,
>
> ...
>
> --- v4.2-rc4.orig/mm/memory.c
> +++ v4.2-rc4/mm/memory.c
> @@ -620,12 +620,12 @@ int __pte_alloc_kernel(pmd_t *pmd, unsigned long address)
> return 0;
> }
>
> -static inline void init_rss_vec(int *rss)
> +inline void init_rss_vec(int *rss)
> {
> memset(rss, 0, sizeof(int) * NR_MM_COUNTERS);
> }
>
> -static inline void add_mm_rss_vec(struct mm_struct *mm, int *rss)
> +inline void add_mm_rss_vec(struct mm_struct *mm, int *rss)
> {
> int i;

The inlines are a bit odd, but this does save ~10 bytes in memory.o for
some reason.