Re: [PATCH] mm/zsmalloc: add trace events for zs_compact

Ganesh Mahendran
2016-06-13T05:14:00Z

2016-06-13 12:42 GMT+08:00 Minchan Kim <minchan@kernel.org>:
> On Wed, Jun 08, 2016 at 02:39:19PM +0800, Ganesh Mahendran wrote:
>
> <snip>
>
>> zsmalloc is not only used by zram, but also zswap. Maybe
>> others in the future.
>>
>> I tried to use function_graph. It seems there are too much log
>> printed:
>> ------
>> root@leo-test:/sys/kernel/debug/tracing# cat trace
>> # tracer: function_graph
>> #
>> # CPU DURATION FUNCTION CALLS
>> # | | | | | | |
>> 2) | zs_compact [zsmalloc]() {
>> 2) | /* zsmalloc_compact_start: pool zram0 */
>> 2) 0.889 us | _raw_spin_lock();
>> 2) 0.896 us | isolate_zspage [zsmalloc]();
>> 2) 0.938 us | _raw_spin_lock();
>> 2) 0.875 us | isolate_zspage [zsmalloc]();
>> 2) 0.942 us | _raw_spin_lock();
>> 2) 0.962 us | isolate_zspage [zsmalloc]();
>> ...
>> 2) 0.879 us | insert_zspage [zsmalloc]();
>> 2) 4.520 us | }
>> 2) 0.975 us | _raw_spin_lock();
>> 2) 0.890 us | isolate_zspage [zsmalloc]();
>> 2) 0.882 us | _raw_spin_lock();
>> 2) 0.894 us | isolate_zspage [zsmalloc]();
>> 2) | /* zsmalloc_compact_end: pool zram0: 0 pages
>> compacted(total 0) */
>> 2) # 1351.241 us | }
>> ------
>> => 1351.241 us used
>>
>> And it seems the overhead of function_graph is bigger than trace event.
>>
>> bash-3682 [002] .... 1439.180646: zsmalloc_compact_start: pool zram0
>> bash-3682 [002] .... 1439.180659: zsmalloc_compact_end: pool zram0:
>> 0 pages compacted(total 0)
>> => 13 us > 1351.241 us
>
> You could use to cut out.
>
> To introduce new event trace to get a elasped time, it's pointless,
> I think.

Agree.

>
> It should have more like pool name you mentioned.
> Like saying other thread, It would be better to show
> [pool name, compact size_class,
> the number of object moved, the number of freed page], IMO.

Thanks for you suggestion!
I would be useful to see compact details for each class.
I will send another patch to do this.

Thanks.

>
> Thanks.