Re: [PATCH 6/8] Add __GFP_OTHER_NODE flag

[KOSAKI Motohiro]

> From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> 
> Add a new __GFP_OTHER_NODE flag to tell the low level numa statistics
> in zone_statistics() that an allocation is on behalf of another thread.
> This way the local and remote counters can be still correct, even
> when background daemons like khugepaged are changing memory
> mappings.
> 
> This only affects the accounting, but I think it's worth doing that
> right to avoid confusing users.
> 
> I first tried to just pass down the right node, but this required
> a lot of changes to pass down this parameter and at least one
> addition of a 10th argument to a 9 argument function. Using
> the flag is a lot less intrusive.

Yes, less intrusive. But are you using current NUMA stastics on
practical system?
I didn't numa stat recent 5 years at all. So, I'm curious your usecase.
IOW, I haven't convinced this is worthful to consume new GFP_ flags bit.

_now_, I can say I don't found any bug in this patch.

> 
> Open: should be also used for migration?
> 
> Cc: aarcange@xxxxxxxxxx
> Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> ---
>  include/linux/gfp.h    |    2 ++
>  include/linux/vmstat.h |    4 ++--
>  mm/page_alloc.c        |    2 +-
>  mm/vmstat.c            |    9 +++++++--
>  4 files changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 814d50e..a064724 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -35,6 +35,7 @@ struct vm_area_struct;
>  #define ___GFP_NOTRACK		0
>  #endif
>  #define ___GFP_NO_KSWAPD	0x400000u
> +#define ___GFP_OTHER_NODE	0x800000u



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