linux-kernel - Re: [PATCH] mm/vmstat: add events for THP max_ptes

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Date:   Mon, 27 Dec 2021 11:19:32 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     cgel.zte@...il.com
Cc:     akpm@...ux-foundation.org, yang.shi@...ux.alibaba.com,
        dave.hansen@...ux.intel.com, yang.yang29@....com.cn,
        minchan@...nel.org, saravanand@...com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm/vmstat: add events for THP max_ptes_* exceeds

cgel.zte@...il.com writes:

> From: Yang Yang <yang.yang29@....com.cn>
>
> There are interfaces to adjust max_ptes_none, max_ptes_swap,
> max_ptes_shared values, see
> /sys/kernel/mm/transparent_hugepage/khugepaged/.
>
> But system administrator maynot know which value is the best. So
> Add those events to support adjusting max_ptes_* to suitable values.
>
> For example, if default max_ptes_swap value causes too much failures,
> and system uses zram whose IO is fast, administrator could increase
> max_ptes_swap until THP_SCAN_EXCEED_SWAP_PTE not increase anymore.
>
> Signed-off-by: Yang Yang <yang.yang29@....com.cn>
> ---
>  include/linux/vm_event_item.h | 3 +++
>  mm/khugepaged.c               | 7 +++++++
>  mm/vmstat.c                   | 3 +++
>  3 files changed, 13 insertions(+)
>
> diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
> index a185cc75ff52..7b2363388bfa 100644
> --- a/include/linux/vm_event_item.h
> +++ b/include/linux/vm_event_item.h
> @@ -98,6 +98,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
>  		THP_SPLIT_PAGE_FAILED,
>  		THP_DEFERRED_SPLIT_PAGE,
>  		THP_SPLIT_PMD,
> +		THP_SCAN_EXCEED_NONE_PTE,
> +		THP_SCAN_EXCEED_SWAP_PTE,
> +		THP_SCAN_EXCEED_SHARED_PTE,

"SCAN" appears too general, how about

  THP_COLLAPSE_EXCEED_SWAP_PTE

?

Best Regards,
Huang, Ying

[snip]