linux-kernel - Re: [PATCH 3/3] Add name fields in shrinker tracepoint definitions

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Date:	Wed, 13 Jul 2016 11:46:51 +0530
From:	Janani Ravichandran <janani.rvchndrn@...il.com>
To:	Tony Jones <tonyj@...e.de>
Cc:	Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, riel@...riel.com,
	akpm@...ux-foundation.org, hannes@...xchg.org,
	vdavydov@...tuozzo.com, mhocko@...e.com,
	mgorman@...hsingularity.net, kirill.shutemov@...ux.intel.com,
	bywxiaobai@....com
Subject: Re: [PATCH 3/3] Add name fields in shrinker tracepoint definitions


> On Jul 13, 2016, at 6:05 AM, Tony Jones <tonyj@...e.de> wrote:
> 
> On 07/11/2016 07:18 AM, Vlastimil Babka wrote:
>> On 07/09/2016 11:05 AM, Janani Ravichandran wrote:
>>> 
>>> 	TP_fast_assign(
>>> +		__entry->name = shr->name;
>>> 		__entry->shr = shr;
>>> 		__entry->shrink = shr->scan_objects;
>>> 		__entry->nid = sc->nid;
>>> @@ -214,7 +216,8 @@ TRACE_EVENT(mm_shrink_slab_start,
>>> 		__entry->total_scan = total_scan;
>>> 	),
>>> 
>>> -	TP_printk("%pF %p: nid: %d objects to shrink %ld gfp_flags %s pgs_scanned %ld lru_pgs %ld cache items %ld delta %lld total_scan %ld",
>>> +	TP_printk("name: %s %pF %p: nid: %d objects to shrink %ld gfp_flags %s pgs_scanned %ld lru_pgs %ld cache items %ld delta %lld total_scan %ld",
>>> +		__entry->name,
>> 
>> Is this legal to do when printing is not done via the /sys ... file 
>> itself, but raw data is collected and then printed by e.g. trace-cmd? 
>> How can it possibly interpret the "char *" kernel pointer?
> 
> I actually had a similar patch set to this,  I was going to post it but Janani beat me to it ;-)
> 
> Vlastimil is correct,  I'll attach my patch below so you can see the difference.  Otherwise you won't get correct behavior passing through perf.

Thanks for that! I will have a look at it.
>   
> 
> I also have a patch which adds a similar latency script (python) but interfaces it into the perf script setup.

I’m looking for pointers for writing latency scripts using tracepoints as I’m new to it. Can I have a look at yours, please?

Thanks :)

Janani.
> 
> Tony
> 
> ---
> 
> Pass shrinker name in shrink slab tracepoints
> 
> Signed-off-by: Tony Jones <tonyj@...e.de>
> ---
> include/trace/events/vmscan.h | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
> index 0101ef3..0a15948 100644
> --- a/include/trace/events/vmscan.h
> +++ b/include/trace/events/vmscan.h
> @@ -16,6 +16,8 @@
> #define RECLAIM_WB_SYNC		0x0004u /* Unused, all reclaim async */
> #define RECLAIM_WB_ASYNC	0x0008u
> 
> +#define SHRINKER_NAME_LEN 	(size_t)32
> +
> #define show_reclaim_flags(flags)				\
> 	(flags) ? __print_flags(flags, "|",			\
> 		{RECLAIM_WB_ANON,	"RECLAIM_WB_ANON"},	\
> @@ -190,6 +192,7 @@ TRACE_EVENT(mm_shrink_slab_start,
> 
> 	TP_STRUCT__entry(
> 		__field(struct shrinker *, shr)
> +		__array(char, name, SHRINKER_NAME_LEN)
> 		__field(void *, shrink)
> 		__field(int, nid)
> 		__field(long, nr_objects_to_shrink)
> @@ -203,6 +206,7 @@ TRACE_EVENT(mm_shrink_slab_start,
> 
> 	TP_fast_assign(
> 		__entry->shr = shr;
> +		strlcpy(__entry->name, shr->name, SHRINKER_NAME_LEN);
> 		__entry->shrink = shr->scan_objects;
> 		__entry->nid = sc->nid;
> 		__entry->nr_objects_to_shrink = nr_objects_to_shrink;
> @@ -214,9 +218,10 @@ TRACE_EVENT(mm_shrink_slab_start,
> 		__entry->total_scan = total_scan;
> 	),
> 
> -	TP_printk("%pF %p: nid: %d objects to shrink %ld gfp_flags %s pgs_scanned %ld lru_pgs %ld cache items %ld delta %lld total_scan %ld",
> +	TP_printk("%pF %p(%s): nid: %d objects to shrink %ld gfp_flags %s pgs_scanned %ld lru_pgs %ld cache items %ld delta %lld total_scan %ld",
> 		__entry->shrink,
> 		__entry->shr,
> +		__entry->name,
> 		__entry->nid,
> 		__entry->nr_objects_to_shrink,
> 		show_gfp_flags(__entry->gfp_flags),
> @@ -236,6 +241,7 @@ TRACE_EVENT(mm_shrink_slab_end,
> 
> 	TP_STRUCT__entry(
> 		__field(struct shrinker *, shr)
> +		__array(char, name, SHRINKER_NAME_LEN)
> 		__field(int, nid)
> 		__field(void *, shrink)
> 		__field(long, unused_scan)
> @@ -246,6 +252,7 @@ TRACE_EVENT(mm_shrink_slab_end,
> 
> 	TP_fast_assign(
> 		__entry->shr = shr;
> +		strlcpy(__entry->name, shr->name, SHRINKER_NAME_LEN);
> 		__entry->nid = nid;
> 		__entry->shrink = shr->scan_objects;
> 		__entry->unused_scan = unused_scan_cnt;
> @@ -254,9 +261,10 @@ TRACE_EVENT(mm_shrink_slab_end,
> 		__entry->total_scan = total_scan;
> 	),
> 
> -	TP_printk("%pF %p: nid: %d unused scan count %ld new scan count %ld total_scan %ld last shrinker return val %d",
> +	TP_printk("%pF %p(%s): nid: %d unused scan count %ld new scan count %ld total_scan %ld last shrinker return val %d",
> 		__entry->shrink,
> 		__entry->shr,
> +		__entry->name,
> 		__entry->nid,
> 		__entry->unused_scan,
> 		__entry->new_scan,
> 
>