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    SubjectRe: [PATCH 1/7] trace/events: Add gup trace events
    On Tue,  1 Dec 2015 15:06:11 -0800
    Yang Shi <yang.shi@linaro.org> wrote:

    > page-faults events record the invoke to handle_mm_fault, but the invoke
    > may come from do_page_fault or gup. In some use cases, the finer event count
    > mey be needed, so add trace events support for:
    >
    > __get_user_pages
    > __get_user_pages_fast
    > fixup_user_fault
    >
    > Signed-off-by: Yang Shi <yang.shi@linaro.org>
    > ---
    > include/trace/events/gup.h | 77 ++++++++++++++++++++++++++++++++++++++++++++++
    > 1 file changed, 77 insertions(+)
    > create mode 100644 include/trace/events/gup.h
    >
    > diff --git a/include/trace/events/gup.h b/include/trace/events/gup.h
    > new file mode 100644
    > index 0000000..37d18f9
    > --- /dev/null
    > +++ b/include/trace/events/gup.h
    > @@ -0,0 +1,77 @@
    > +#undef TRACE_SYSTEM
    > +#define TRACE_SYSTEM gup
    > +
    > +#if !defined(_TRACE_GUP_H) || defined(TRACE_HEADER_MULTI_READ)
    > +#define _TRACE_GUP_H
    > +
    > +#include <linux/types.h>
    > +#include <linux/tracepoint.h>
    > +
    > +TRACE_EVENT(gup_fixup_user_fault,
    > +
    > + TP_PROTO(struct task_struct *tsk, struct mm_struct *mm,
    > + unsigned long address, unsigned int fault_flags),
    > +
    > + TP_ARGS(tsk, mm, address, fault_flags),
    > +
    > + TP_STRUCT__entry(
    > + __array( char, comm, TASK_COMM_LEN )

    Why save the comm? The tracing infrastructure should keep track of that.

    > + __field( unsigned long, address )
    > + ),
    > +
    > + TP_fast_assign(
    > + memcpy(__entry->comm, tsk->comm, TASK_COMM_LEN);
    > + __entry->address = address;
    > + ),
    > +
    > + TP_printk("comm=%s address=%lx", __entry->comm, __entry->address)
    > +);
    > +
    > +TRACE_EVENT(gup_get_user_pages,
    > +
    > + TP_PROTO(struct task_struct *tsk, struct mm_struct *mm,
    > + unsigned long start, unsigned long nr_pages,
    > + unsigned int gup_flags, struct page **pages,
    > + struct vm_area_struct **vmas, int *nonblocking),
    > +
    > + TP_ARGS(tsk, mm, start, nr_pages, gup_flags, pages, vmas, nonblocking),

    Why so many arguments? Most are not used.

    -- Steve

    > +
    > + TP_STRUCT__entry(
    > + __array( char, comm, TASK_COMM_LEN )
    > + __field( unsigned long, start )
    > + __field( unsigned long, nr_pages )
    > + ),
    > +
    > + TP_fast_assign(
    > + memcpy(__entry->comm, tsk->comm, TASK_COMM_LEN);
    > + __entry->start = start;
    > + __entry->nr_pages = nr_pages;
    > + ),
    > +
    > + TP_printk("comm=%s start=%lx nr_pages=%lu", __entry->comm, __entry->start, __entry->nr_pages)
    > +);
    > +
    > +TRACE_EVENT(gup_get_user_pages_fast,
    > +
    > + TP_PROTO(unsigned long start, int nr_pages, int write,
    > + struct page **pages),
    > +
    > + TP_ARGS(start, nr_pages, write, pages),
    > +
    > + TP_STRUCT__entry(
    > + __field( unsigned long, start )
    > + __field( unsigned long, nr_pages )
    > + ),
    > +
    > + TP_fast_assign(
    > + __entry->start = start;
    > + __entry->nr_pages = nr_pages;
    > + ),
    > +
    > + TP_printk("start=%lx nr_pages=%lu", __entry->start, __entry->nr_pages)
    > +);
    > +
    > +#endif /* _TRACE_GUP_H */
    > +
    > +/* This part must be outside protection */
    > +#include <trace/define_trace.h>



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