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

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Message-ID: <56608BCA.3030303@linaro.org>
Date:	Thu, 03 Dec 2015 10:36:58 -0800
From:	"Shi, Yang" <yang.shi@...aro.org>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	akpm@...ux-foundation.org, mingo@...hat.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH V2 1/7] trace/events: Add gup trace events

On 12/2/2015 8:07 PM, Steven Rostedt wrote:
> On Wed,  2 Dec 2015 14:53:27 -0800
> Yang Shi <yang.shi@...aro.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@...aro.org>
>> ---
>>   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().

Thanks for the suggestion, will fix them in V3.

Regards,
Yang

>
> -- 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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