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

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Message-Id: <20150807155537.d483456f753355059f9ce10a@linux-foundation.org>
Date:	Fri, 7 Aug 2015 15:55:37 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	David Rientjes <rientjes@...gle.com>,
	Jörn Engel <joern@...estorage.com>,
	Mike Kravetz <mike.kravetz@...cle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Naoya Horiguchi <nao.horiguchi@...il.com>
Subject: Re: [PATCH v2 2/2] mm: hugetlb: add VmHugetlbRSS: field in
 /proc/pid/status

On Fri, 7 Aug 2015 07:24:50 +0000 Naoya Horiguchi <n-horiguchi@...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.


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