Re: [PATCH V2 1/7] trace/events: Add gup trace events

From: Steven Rostedt
Date: Wed Dec 02 2015 - 23:09:19 EST


On Wed, 2 Dec 2015 14:53:27 -0800
Yang Shi <yang.shi@xxxxxxxxxx> 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@xxxxxxxxxx>
> ---
> include/trace/events/gup.h | 71 ++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 71 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..03a4674
> --- /dev/null
> +++ b/include/trace/events/gup.h
> @@ -0,0 +1,71 @@
> +#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),

Arges added and not used by TP_fast_assign(), this will slow down the
code while tracing is enabled, as they need to be added to the trace
function call.

> +
> + TP_STRUCT__entry(
> + __field( unsigned long, address )
> + ),
> +
> + TP_fast_assign(
> + __entry->address = address;
> + ),
> +
> + TP_printk("address=%lx", __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),
> +
> + TP_ARGS(tsk, mm, start, nr_pages),

Here too but this is worse. See below.

> +
> + 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)
> +);
> +
> +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),

This and the above "gup_get_user_pages" have the same entry field,
assign and printk. They should be combined into a DECLARE_EVENT_CLASS()
and two DEFINE_EVENT()s. That will save on size as the
DECLARE_EVENT_CLASS() is the biggest part of each TRACE_EVENT().

-- Steve


> +
> + 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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