[ oprofile-Bugs-2646425 ] opreport side-by-side archive comparison fails

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Bugs item #2646425, was opened at 2009-02-27 13:54
Message generated for change (Comment added) made by maynardj
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 9
Private: No
Submitted By: Jim Blandy (jimblandy)
Assigned to: Maynard Johnson (maynardj)
Summary: opreport side-by-side archive comparison fails

Initial Comment:
When I use opreport to compare two archives, to measure the effect of a change to a program, opreport doesn't show the change between the two archives.

I have two archives named op-in and op-lazy, in which I've run an executable (at the same path in both archives).  When I use opreport on each archive individually, the difference in the sample count for the top function is clear:

$ opreport -xl archive:op-in | head
CPU: Core 2, speed 800 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (Unhalted core cycles) count 100000
samples  %        symbol name
34469015 63.9760  js_Interpret
5160045   9.5773  js_ExecuteRegExp
1527153   2.8345  js_NewDoubleInRootedValue
866500    1.6083  js_SearchScope
644681    1.1966  js_DoubleToECMAInt32
630017    1.1693  PushBackTrackState(REGlobalData*, REOp, unsigned char*, REMatchState*, unsigned short const*, unsigned int, unsigned int)
571575    1.0609  __i686.get_pc_thunk.bx
$ opreport -xl archive:op-lazy | head
CPU: Core 2, speed 800 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (Unhalted core cycles) count 100000
samples  %        symbol name
34878417 64.3587  js_Interpret
5172438   9.5443  js_ExecuteRegExp
1522564   2.8095  js_NewDoubleInRootedValue
863839    1.5940  js_SearchScope
649108    1.1978  js_DoubleToECMAInt32
626030    1.1552  PushBackTrackState(REGlobalData*, REOp, unsigned char*, REMatchState*, unsigned short const*, unsigned int, unsigned int)
543344    1.0026  __i686.get_pc_thunk.bx
$ 

Note js_Interpret got 101% as many samples in op-lazy as it did in op-in.  However, a side-by-side comparison doesn't show that:

$ opreport -xl { archive:op-in } { archive:op-lazy } | head
CPU: Core 2, speed 800 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (Unhalted core cycles) count 100000
samples  %        diff %    symbol name
34878417 64.3587        0   js_Interpret
5172438   9.5443        0   js_ExecuteRegExp
1522564   2.8095        0   js_NewDoubleInRootedValue
863839    1.5940        0   js_SearchScope
649108    1.1978        0   js_DoubleToECMAInt32
626030    1.1552        0   PushBackTrackState(REGlobalData*, REOp, unsigned char*, REMatchState*, unsigned short const*, unsigned int, unsigned int)
543344    1.0026        0   __i686.get_pc_thunk.bx
$ 

I would expect to see a 1% difference reported in the entry for js_Interpret.


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>Comment By: Maynard Johnson (maynardj)
Date: 2009-03-23 14:08

Message:
My previous comment was incorrect due to a user error of mine when trying
to diff two profiles.  So now, using the current oprofile cvs, I am able to
get a correct differential profile.  The symptom reported in this bug of 0%
differences for the symbols is not reproducible with current cvs. 

Jim, please re-try your profile diff with current cvs. 

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Comment By: Maynard Johnson (maynardj)
Date: 2009-03-19 16:53

Message:
AFAICT, differential profiles has never worked.  I reproduced the problem
on current cvs, so then I went back and installed 0.9, where this feature
was first introduced.  It didn't work there either.  I will continue to
investigate.

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Comment By: Jim Blandy (jimblandy)
Date: 2009-03-01 19:15

Message:
If you have trouble reproducing this, I can put the two archives up for you
to download.  (They're 17MB each, but having the right data can make all
the difference.)


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Comment By: John Levon (movement)
Date: 2009-02-28 09:03

Message:
It sounds like diff mode is completely broken, serious bug. Maynard?

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