Re: [PATCH] Document the new Anonymous field in smaps.

Hugh Dickins
2010-09-16T16:50:34Z

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On Thu, 16 Sep 2010, Nikanth Karthikesan wrote:

> Sorry, I missed to add documentation, when I sent the patch. This depends on
> the patch titled, "[PATCH] Export amount of anonymous memory in a mapping via
> smaps".
>
> Thanks
> Nikanth
>
>
> Document the new Anonymous field in smaps.
>
> Signed-off-by: Nikanth Karthikesan <knikanth@suse.de>

Thanks for adding this, but...

>
> ---
>
> diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
> index a6aca87..75c7368 100644
> --- a/Documentation/filesystems/proc.txt
> +++ b/Documentation/filesystems/proc.txt
> @@ -370,6 +370,7 @@ Shared_Dirty: 0 kB
> Private_Clean: 0 kB
> Private_Dirty: 0 kB
> Referenced: 892 kB
> +Anonymous: 0 kB
> Swap: 0 kB
> KernelPageSize: 4 kB
> MMUPageSize: 4 kB
> @@ -380,7 +381,10 @@ the amount of the mapping that is currently resident in RAM, the "proportional
> set size” (divide each shared page by the number of processes sharing it), the
> number of clean and dirty shared pages in the mapping, and the number of clean
> and dirty private pages in the mapping. The "Referenced" indicates the amount
> -of memory currently marked as referenced or accessed.
> +of memory currently marked as referenced or accessed. The "Anonymous" shows
> +the amount of mapping that is not associated with a file. Even the private
> +pages in a mapping associated with a file, would become anonymous, when they
> +are modified.

... unfortunately it needs rewording, because you're describing it well
with respect to MAP_SHARED versus MAP_PRIVATE, but /proc/pid/smaps has a
different definition of whether pages are shared or private, just depending
on their mapcount at the instant.

Indeed, adding a comment on that would be helpful too, if you've time.

>
> This file is only present if the CONFIG_MMU kernel configuration option is
> enabled.