Re: [PATCH] Export amount of anonymous memory in a mapping via smaps

[Hugh Dickins <hughd@google.com>]

On Thu, 16 Sep 2010, Nikanth Karthikesan wrote:

> Export the number of anonymous pages in a mapping via smaps.
> 
> Even the private pages in a mapping backed by a file, would be marked as
> anonymous, when they are modified. Export this information to user-space via
> smaps.
> 
> Signed-off-by: Nikanth Karthikesan <knikanth@suse.de>

Acked-by: Hugh Dickins <hughd@google.com>

but I'd prefer if we added a little more justification, such as:

Exporting this count will help gdb to make a better decision on which
areas need to be dumped in its coredump; and should be useful to others
studying the memory usage of a process.

> 
> ---
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 439fc1f..3c18fc8 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -326,6 +326,7 @@ struct mem_size_stats {
>  	unsigned long private_clean;
>  	unsigned long private_dirty;
>  	unsigned long referenced;
> +	unsigned long anonymous;
>  	unsigned long swap;
>  	u64 pss;
>  };
> @@ -356,6 +357,9 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
>  		if (!page)
>  			continue;
>  
> +		if (PageAnon(page))
> +			mss->anonymous += PAGE_SIZE;
> +
>  		mss->resident += PAGE_SIZE;
>  		/* Accumulate the size in pages that have been accessed. */
>  		if (pte_young(ptent) || PageReferenced(page))
> @@ -409,6 +413,7 @@ static int show_smap(struct seq_file *m, void *v)
>  		   "Private_Clean:  %8lu kB\n"
>  		   "Private_Dirty:  %8lu kB\n"
>  		   "Referenced:     %8lu kB\n"
> +		   "Anonymous:      %8lu kB\n"
>  		   "Swap:           %8lu kB\n"
>  		   "KernelPageSize: %8lu kB\n"
>  		   "MMUPageSize:    %8lu kB\n",
> @@ -420,6 +425,7 @@ static int show_smap(struct seq_file *m, void *v)
>  		   mss.private_clean >> 10,
>  		   mss.private_dirty >> 10,
>  		   mss.referenced >> 10,
> +		   mss.anonymous >> 10,
>  		   mss.swap >> 10,
>  		   vma_kernel_pagesize(vma) >> 10,
>  		   vma_mmu_pagesize(vma) >> 10);
> 
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