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

Andrew Morton
2021-03-06T00:57:49Z

On Thu, 18 Feb 2021 15:57:44 -0800 Saravanan D <saravanand@fb.com> 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?