linux-kernel - Re: [PATCH v16 22/23] tracing: Add hist trigger 'log2' modifier

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Date:	Tue, 29 Mar 2016 12:01:40 +0200
From:	Daniel Wagner <wagi@...om.org>
To:	Tom Zanussi <tom.zanussi@...ux.intel.com>, rostedt@...dmis.org
Cc:	masami.hiramatsu.pt@...achi.com, namhyung@...nel.org,
	josh@...htriplett.org, andi@...stfloor.org,
	mathieu.desnoyers@...icios.com, peterz@...radead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v16 22/23] tracing: Add hist trigger 'log2' modifier

Hi,

On 03/03/2016 07:55 PM, Tom Zanussi wrote:
> When using '.log2' modifier, the output looks like:
> 
>   # echo 'hist:key=bytes_req.log2' > kmalloc/trigger
>   # cat kmalloc/hist
> 
>   { bytes_req: ~ 2^12 } hitcount:          1
>   { bytes_req: ~ 2^11 } hitcount:          1
>   { bytes_req: ~ 2^9  } hitcount:          2
>   { bytes_req: ~ 2^6  } hitcount:          3
>   { bytes_req: ~ 2^3  } hitcount:         13
>   { bytes_req: ~ 2^5  } hitcount:         19
>   { bytes_req: ~ 2^8  } hitcount:         49
>   { bytes_req: ~ 2^7  } hitcount:         57
>   { bytes_req: ~ 2^4  } hitcount:         74


I found a small inconsistency. My command line is

  echo 'hist:key=latency.log2:sort=latency' > /sys/kernel/debug/tracing/events/test/latency_complete/trigger

When looking at the output of 'hist' you see that the 
'sort=' is not what I provided.

cat /sys/kernel/debug/tracing/events/test/latency_complete/hist
# event histogram
#
# trigger info: hist:keys=latency.log2:vals=hitcount:sort=latency.log2:size=2048 [active]
#
#

This is not terrible important. 

cheers,
daniel