[Devel] [PATCH rh7] mm/page_alloc: fix latency in tracepoint.

[Evgenii Shatokhin]

On 06.03.2019 21:38, Denis Lunev wrote:
> On 3/6/19 7:12 PM, Andrey Ryabinin wrote:
>> Since transition from jiffies to sched_clock(), mm_page_alloc
>> garbadge since we substract from jiffies nanoseconds.
>> Fix this.
>>
>> Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
>> ---
>>   include/trace/events/kmem.h |  2 +-
>>   mm/page_alloc.c             | 12 ++++++------
>>   2 files changed, 7 insertions(+), 7 deletions(-)
>>
>> diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
>> index af1a8ffb106b..9ecda0f99463 100644
>> --- a/include/trace/events/kmem.h
>> +++ b/include/trace/events/kmem.h
>> @@ -213,7 +213,7 @@ TRACE_EVENT(mm_page_alloc,
>>   		__entry->migratetype	= migratetype;
>>   	),
>>   
>> -	TP_printk("page=%p pfn=%lu order=%d migratetype=%d gfp_flags=%s lat=%d",
>> +	TP_printk("page=%p pfn=%lu order=%d migratetype=%d gfp_flags=%s lat=%lld",
>>   		__entry->page,
>>   		__entry->page ? page_to_pfn(__entry->page) : 0,
>>   		__entry->order,
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 362c2a2235c1..134c93a1962b 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -3464,14 +3464,13 @@ void update_maxlat(struct kstat_lat_snap_struct *alloc_lat,
>>   }
>>   
>>   static void __alloc_collect_stats(gfp_t gfp_mask, unsigned int order,
>> -		struct page *page, u64 time)
>> +		struct page *page, u64 time, u64 current_clock)
>>   {
>>   #ifdef CONFIG_VE
>>   	unsigned long flags;
>> -	u64 current_clock, delta;
>> +	u64 delta;
>>   	int ind, cpu;
>>   
>> -	current_clock = sched_clock();
>>   	delta = current_clock - time;
>>   	if (!(gfp_mask & __GFP_WAIT)) {
>>   		if (in_task())
>> @@ -3547,7 +3546,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
>>   	int migratetype = allocflags_to_migratetype(gfp_mask);
>>   	unsigned int cpuset_mems_cookie;
>>   	int alloc_flags = ALLOC_WMARK_LOW|ALLOC_CPUSET|ALLOC_FAIR;
>> -	u64 start;
>> +	u64 start, current_clock;
>>   
>>   	gfp_mask &= gfp_allowed_mask;
>>   
>> @@ -3618,9 +3617,10 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
>>   				preferred_zone, migratetype);
>>   	}
>>   
>> -	__alloc_collect_stats(gfp_mask, order, page, start);
>> +	current_clock = sched_clock();
>> +	__alloc_collect_stats(gfp_mask, order, page, start, current_clock);
>>   	trace_mm_page_alloc(page, order, gfp_mask, migratetype,
>> -			jiffies_to_usecs(jiffies - start));
>> +			(current_clock - start));
>>   
>>   out:
>>   	/*
> and this is 120% not enough!!
> 
> diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
> index af1a8ffb106b..49153bbacb95 100644
> --- a/include/trace/events/kmem.h
> +++ b/include/trace/events/kmem.h
> @@ -211,6 +211,7 @@ TRACE_EVENT(mm_page_alloc,
>                  __entry->order          = order;
>                  __entry->gfp_flags      = gfp_flags;
>                  __entry->migratetype    = migratetype;
> +               __entry->time       = time;
>          ),
>   
>          TP_printk("page=%p pfn=%lu order=%d migratetype=%d gfp_flags=%s
> lat=%d",
> iris ~/src/git/linux-vz7 $
> 
> This hunk __MUST__ be added to RK!

I adapted thus hunk to RK and prepared a binary patch from it for the 
kernel vz7.73.29.

Files, details and usage instructions are here:
https://jira.sw.ru/browse/PSBM-92391

I suppose, it should be enough for kernel debugging and such.

> 
> Den
> 
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