Re: opreport on time window of operf data

William Cohen <[email protected]> wrote on 03/24/2015 08:56:48 AM:

> From: William Cohen <[email protected]>
> To: Henry May/Rochester/IBM@IBMUS, [email protected]
> Date: 03/24/2015 08:57 AM
> Subject: Re: opreport on time window of operf data
> 
> On 03/23/2015 08:24 AM, Henry May wrote:
> > Is there a way to make opreport only process events that occurred 
> in a subset window of the total operf collection time?  I have a 
> long running workload that occasionally sees a spike in L2 misses. 
> I can determine when this happens because throughput drops.  I'd 
> like to profile the workload, but only consider events that fall 
> within the window of decreased throughput when generating the opreport.
> > 
> > 
> 
> Hi Henry,
> 
> operf doesn't have a convenient mechanism to control when the data 
> is collected.  If operf is collecting data for a process that is 
> spawned by operf, it will collect data for the lifetime of the 
> child.  As a kludge you might get a smaller duration measurement by 
> having operf attach to the currently running process with  "--pid 
> <pid>" option when the dip in throughput starts and then interrupt 
> operf with ctl-c or "kill -2 <operf_pid>" when want to stop data 
collection.
Thanks Will.  I don't think I expressed my thinking clearly.  The feature 
I want would actually be on opreport.  I want operf to collect over the 
entire long interval. Then after identifying the shorter subset interval 
where throughput drops I would specify the start and end times on opreport 
- maybe something like:

opreport --start-time=<subset start> --stop-time=<subset end>

opreport would generate the histogram, but only include the profiling 
events that fall in the specified subset interval. 

> 
> A couple other possible things that might affect L2 performance are 
> other processes polluting/invalidating the cache and the task being 
> migrated between processors. 
> 
> -Will
> 
> > Henry May
> > IBM InfoSphere Streams Performance
> > [email protected]
> > 720-342-8873
> > Tie: 963-8873
> > 
> > 
> > 
> 
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