Re: [PATCH V6] x86/mm: Tracking linear mapping split events

[Andrew Morton]

On Thu, 18 Feb 2021 15:57:44 -0800 Saravanan D <saravanand@xxxxxx> wrote:

> To help with debugging the sluggishness caused by TLB miss/reload,
> we introduce monotonic hugepage [direct mapped] split event counts since
> system state: SYSTEM_RUNNING to be displayed as part of
> /proc/vmstat in x86 servers
>
> ...
>
> --- a/arch/x86/mm/pat/set_memory.c
> +++ b/arch/x86/mm/pat/set_memory.c
> @@ -120,6 +120,10 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
>  #ifdef CONFIG_SWAP
>  		SWAP_RA,
>  		SWAP_RA_HIT,
> +#endif
> +#ifdef CONFIG_X86
> +		DIRECT_MAP_LEVEL2_SPLIT,
> +		DIRECT_MAP_LEVEL3_SPLIT,
>  #endif
>  		NR_VM_EVENT_ITEMS
>  };

This is the first appearance of arch-specific fields in /proc/vmstat.

I don't really see a problem with this - vmstat is basically a dumping
ground of random developer stuff.  But was this the best place in which
to present this data?