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

From: Zach O'Keefe <zokeefe@google.com>
To: Yang Shi <shy828301@gmail.com>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	linux-api@vger.kernel.org,
	Axel Rasmussen <axelrasmussen@google.com>,
	James Houghton <jthoughton@google.com>,
	Hugh Dickins <hughd@google.com>,
	Miaohe Lin <linmiaohe@huawei.com>,
	David Hildenbrand <david@redhat.com>,
	David Rientjes <rientjes@google.com>,
	Matthew Wilcox <willy@infradead.org>,
	Pasha Tatashin <pasha.tatashin@soleen.com>,
	Peter Xu <peterx@redhat.com>,
	Rongwei Wang <rongwei.wang@linux.alibaba.com>,
	SeongJae Park <sj@kernel.org>, Song Liu <songliubraving@fb.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Chris Kennelly <ckennelly@google.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Minchan Kim <minchan@kernel.org>,
	Patrick Xia <patrickx@google.com>
Subject: Re: [PATCH mm-unstable v3 04/10] mm/khugepaged: add tracepoint to hpage_collapse_scan_file()
Date: Fri, 16 Sep 2022 16:05:37 -0700	[thread overview]
Message-ID: <YyUBQbIgLmAoAOLo@google.com> (raw)
In-Reply-To: <CAHbLzko9MsLcKhV9hh_0ZN8j5Zqh9cvLTCOrhNXGRcVYWQ1q3g@mail.gmail.com>

On Sep 16 13:41, Yang Shi wrote:
> 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>
> 

Thanks, as always!

> > ---
> >  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
> >