Re: [PATCH mm-unstable v3 04/10] mm/khugepaged: add tracepoint to hpage_collapse_scan_file()

[Yang Shi <shy828301@gmail.com>]

On Wed, Sep 7, 2022 at 7:45 AM Zach O'Keefe <zokeefe@google.com> wrote:
>
> Add huge_memory:trace_mm_khugepaged_scan_file tracepoint to
> hpage_collapse_scan_file() analogously to hpage_collapse_scan_pmd().
> While this change is targeted at debugging MADV_COLLAPSE pathway, the
> "mm_khugepaged" prefix is retained for symmetry with
> huge_memory:trace_mm_khugepaged_scan_pmd, which retains it's legacy name
> to prevent changing kernel ABI as much as possible.
>
> Signed-off-by: Zach O'Keefe <zokeefe@google.com>

Reviewed-by: Yang Shi <shy828301@gmail.com>

> ---
>  include/trace/events/huge_memory.h | 34 ++++++++++++++++++++++++++++++
>  mm/khugepaged.c                    |  3 ++-
>  2 files changed, 36 insertions(+), 1 deletion(-)
>
> diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
> index df33453b70fc..935af4947917 100644
> --- a/include/trace/events/huge_memory.h
> +++ b/include/trace/events/huge_memory.h
> @@ -169,5 +169,39 @@ TRACE_EVENT(mm_collapse_huge_page_swapin,
>                 __entry->ret)
>  );
>
> +TRACE_EVENT(mm_khugepaged_scan_file,
> +
> +       TP_PROTO(struct mm_struct *mm, struct page *page, const char *filename,
> +                int present, int swap, int result),
> +
> +       TP_ARGS(mm, page, filename, present, swap, result),
> +
> +       TP_STRUCT__entry(
> +               __field(struct mm_struct *, mm)
> +               __field(unsigned long, pfn)
> +               __string(filename, filename)
> +               __field(int, present)
> +               __field(int, swap)
> +               __field(int, result)
> +       ),
> +
> +       TP_fast_assign(
> +               __entry->mm = mm;
> +               __entry->pfn = page ? page_to_pfn(page) : -1;
> +               __assign_str(filename, filename);
> +               __entry->present = present;
> +               __entry->swap = swap;
> +               __entry->result = result;
> +       ),
> +
> +       TP_printk("mm=%p, scan_pfn=0x%lx, filename=%s, present=%d, swap=%d, result=%s",
> +               __entry->mm,
> +               __entry->pfn,
> +               __get_str(filename),
> +               __entry->present,
> +               __entry->swap,
> +               __print_symbolic(__entry->result, SCAN_STATUS))
> +);
> +
>  #endif /* __HUGE_MEMORY_H */
>  #include <trace/define_trace.h>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 66457a06b4e7..9325aec25abc 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -2152,7 +2152,8 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
>                 }
>         }
>
> -       /* TODO: tracepoints */
> +       trace_mm_khugepaged_scan_file(mm, page, file->f_path.dentry->d_iname,
> +                                     present, swap, result);
>         return result;
>  }
>  #else
> --
> 2.37.2.789.g6183377224-goog
>