Re: [mm-unstable v7 11/18] mm/madvise: add huge_memory:mm_madvise_collapse tracepoint

[Yang Shi <shy828301@gmail.com>]

On Wed, Jul 6, 2022 at 5:06 PM Zach O'Keefe <zokeefe@google.com> wrote:
>
> Add a tracepoint to expose mm, address, and enum scan_result of each
> hugepage attempted to be collapsed by call to madvise(MADV_COLLAPSE).

Is this necessary? Isn't mm_khugepaged_scan_pmd tracepoint good
enough? It doesn't have "address", but you should be able to calculate
address from it with syscall trace together.


>
> Signed-off-by: Zach O'Keefe <zokeefe@google.com>
> ---
>  include/trace/events/huge_memory.h | 22 ++++++++++++++++++++++
>  mm/khugepaged.c                    |  2 ++
>  2 files changed, 24 insertions(+)
>
> diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
> index 55392bf30a03..38d339ffdb16 100644
> --- a/include/trace/events/huge_memory.h
> +++ b/include/trace/events/huge_memory.h
> @@ -167,5 +167,27 @@ TRACE_EVENT(mm_collapse_huge_page_swapin,
>                 __entry->ret)
>  );
>
> +TRACE_EVENT(mm_madvise_collapse,
> +
> +       TP_PROTO(struct mm_struct *mm, unsigned long addr, int result),
> +
> +       TP_ARGS(mm, addr, result),
> +
> +       TP_STRUCT__entry(__field(struct mm_struct *, mm)
> +                        __field(unsigned long, addr)
> +                        __field(int, result)
> +       ),
> +
> +       TP_fast_assign(__entry->mm = mm;
> +                      __entry->addr = addr;
> +                      __entry->result = result;
> +       ),
> +
> +       TP_printk("mm=%p addr=%#lx result=%s",
> +                 __entry->mm,
> +                 __entry->addr,
> +                 __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 e0d00180512c..0207fc0a5b2a 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -2438,6 +2438,8 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
>                 if (!mmap_locked)
>                         *prev = NULL;  /* Tell caller we dropped mmap_lock */
>
> +               trace_mm_madvise_collapse(mm, addr, result);
> +
>                 switch (result) {
>                 case SCAN_SUCCEED:
>                 case SCAN_PMD_MAPPED:
> --
> 2.37.0.rc0.161.g10f37bed90-goog
>