linux-kernel - Re: [PATCH 1/4] mm: khugepaged: add trace_mm_khugepaged

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Message-ID: <eblxs7da63lg3bgbngq22kprlkxv5ggzpkfcktg4pl756tqzse@tk5gyu3ytcja>
Date: Fri, 19 Dec 2025 13:21:14 +0800
From: Vernon Yang <vernon2gm@...il.com>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>
Cc: akpm@...ux-foundation.org, lorenzo.stoakes@...cle.com, ziy@...dia.com, 
	baohua@...nel.org, lance.yang@...ux.dev, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, Vernon Yang <yanglincheng@...inos.cn>
Subject: Re: [PATCH 1/4] mm: khugepaged: add trace_mm_khugepaged_scan event

On Thu, Dec 18, 2025 at 10:24:05AM +0100, David Hildenbrand (Red Hat) wrote:
> On 12/15/25 10:04, Vernon Yang wrote:
> > Add mm_khugepaged_scan event to track the total time for full scan
> > and the total number of pages scanned of khugepaged.
> >
> > Signed-off-by: Vernon Yang <yanglincheng@...inos.cn>
> > ---
> >   include/trace/events/huge_memory.h | 24 ++++++++++++++++++++++++
> >   mm/khugepaged.c                    |  2 ++
> >   2 files changed, 26 insertions(+)
> >
> > diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
> > index dd94d14a2427..b2824c2f8238 100644
> > --- a/include/trace/events/huge_memory.h
> > +++ b/include/trace/events/huge_memory.h
> > @@ -237,5 +237,29 @@ TRACE_EVENT(mm_khugepaged_collapse_file,
> >   		__print_symbolic(__entry->result, SCAN_STATUS))
> >   );
> > +TRACE_EVENT(mm_khugepaged_scan,
> > +
> > +	TP_PROTO(struct mm_struct *mm, int progress, bool full),
> > +
> > +	TP_ARGS(mm, progress, full),
> > +
> > +	TP_STRUCT__entry(
> > +		__field(struct mm_struct *, mm)
> > +		__field(int, progress)
> > +		__field(bool, full)
> > +	),
> > +
> > +	TP_fast_assign(
> > +		__entry->mm = mm;
> > +		__entry->progress = progress;
> > +		__entry->full = full;
> > +	),
> > +
> > +	TP_printk("mm=%p, progress=%d, full=%d",
> > +		__entry->mm,
> > +		__entry->progress,
> > +		__entry->full)
> > +);
> > +
> >   #endif /* __HUGE_MEMORY_H */
> >   #include <trace/define_trace.h>
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index abe54f0043c7..0598a19a98cc 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -2516,6 +2516,8 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
> >   		collect_mm_slot(slot);
> >   	}
> > +	trace_mm_khugepaged_scan(mm, progress, khugepaged_scan.mm_slot == NULL);
> > +
> >   	return progress;
> >   }
>
> Nothing jumped at me, except that "full" could be called
> "full_scan_finished" or smth like that.

Thanks for your review. The full_scan_finished sounds good to me, I'll
do it in the next version.

>
> Acked-by: David Hildenbrand (Red Hat) <david@...nel.org>
>
> --
> Cheers
>
> David

--
Thanks,
Vernon