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Re: [PerfSuite-users] Questions about "Wall clock time"
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From: <rk...@il...> - 2009-11-16 17:44:19
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Jie -
My initial guess is that psprocess is miscalculating the wall clock time you mention. To be sure, I would like to see the original XML document that you got from the benchmark (the complete document). Can you please send me a copy?
The wall clock you found in the XML document is not (I believe) displayed by psprocess, but in this instance it would seem to be more accurate; I am saying that based on its agreement with the "time" command.
The difference between these two measures of time is that one is calculated from the elapsed clock ticks (this is the one that is off in your report); the other is gotten from information taken from the /proc filesystem related to the process/thread being measured. Another important difference is that the first is meant to be literally "wall clock time", while the second is "CPU time" where this is the amount of time actually spent using the processor (these can be very different depending on the application).
Rick
----- Original Message -----
From: "Jie Jiang" <jj...@nu...>
To: rk...@il...
Cc: per...@li...
Sent: Monday, November 16, 2009 8:03:13 AM GMT -06:00 US/Canada Central
Subject: [PerfSuite-users] Questions about "Wall clock time"
Hi Rick,
When processing the collected data with "psprocess", it always show the
"Wall clock time" result.
I have two questions about the "Wall clock time".
First, it is much larger than the run time of the target program.
[root@node2 bin]# time psrun -c test_config1.xml ./cg.A
libpsrun.c:181 : SIGPROF ignored on startup. Handler=0x1, flags=14000000
PerfSuite debugging enabled (debug level: PS_DEBUG_OFF) [PID 5562]
Library version: threaded
[PID 5562] Environment (entry of psrun_init)
[PID 5562] PSRUN_DOFORK = (null)
[PID 5562] LD_PRELOAD = libpsrun.so.0
[PID 5562] PSRUN_PID = 5562
[PID 5562] PS_HWPC_FILE = cg.A
NAS Parallel Benchmarks (NPB3.2-SER) - CG Benchmark
Size: 14000
Iterations: 15
Initialization time = 0.656 seconds
iteration ||r|| zeta
1 0.25789587124191E-12 19.9997581277040
2 0.25434985977194E-14 17.1140495745506
3 0.25346577542259E-14 17.1296668946143
4 0.25342984287709E-14 17.1302113581192
5 0.25247550490803E-14 17.1302338856353
6 0.25375789728060E-14 17.1302349879482
7 0.25309911213776E-14 17.1302350498916
8 0.24971158788969E-14 17.1302350537510
9 0.24662516791025E-14 17.1302350540101
10 0.25086578290790E-14 17.1302350540284
11 0.24878397192172E-14 17.1302350540298
12 0.24359141964394E-14 17.1302350540299
13 0.24247346800617E-14 17.1302350540299
14 0.24157219672237E-14 17.1302350540299
15 0.24243304908282E-14 17.1302350540299
Benchmark completed
VERIFICATION SUCCESSFUL
Zeta is 0.171302350540E+02
Error is 0.526781606656E-13
CG Benchmark Completed.
Class = A
Size = 14000
Iterations = 15
Time in seconds = 2.06
Mop/s total = 724.79
Operation type = floating point
Verification = SUCCESSFUL
Version = 3.2.1
Compile date = 09 Nov 2009
Compile options:
F77 = ifort
FLINK = $(F77)
F_LIB = (none)
F_INC = (none)
FFLAGS = -O -g
FLINKFLAGS = -O
RAND = randi8
Please send all errors/feedbacks to:
NPB Development Team
np...@na...
real 0m2.756s
user 0m2.711s
sys 0m0.022s
[root@node2 bin]# psprocess -m test_metric.xml cg.A.5562.node2.xml
PerfSuite Hardware Performance Summary Report
Version : 1.0
Created : Mon Nov 16 20:46:23 CST 2009
Generator : psprocess 0.5
XML Source : cg.A.5562.node2.xml
Execution Information
============================================================================================
Collector : libpshwpc
Date : Mon Nov 16 20:45:34 2009
Host : node2
Process ID : 5562
Thread : 0
User : root
Command : cg.A
Processor and System Information
============================================================================================
Node CPUs : 8
Vendor : Intel
Family : Pentium Pro (P6)
Brand : Intel(R) Xeon(R) CPU E5540 @
2.53GHz
CPU Revision : 5
Clock (MHz) : 1600.000
Memory (MB) : 16078.69
Pagesize (KB) : 4
Cache Information
============================================================================================
Cache levels : 3
--------------------------------
Level 1
Type : instruction
Size (KB) : 32
Linesize (B) : 64
Assoc : 4
Type : data
Size (KB) : 32
Linesize (B) : 64
Assoc : 8
--------------------------------
Level 2
Type : unified
Size (KB) : 256
Linesize (B) : 64
Assoc : 8
--------------------------------
Level 3
Type : unified
Size (KB) : 8192
Linesize (B) : 64
Assoc : 16
Index Description
Counter Value
============================================================================================
1 MEM_LOAD_RETIRED:LLC_UNSHARED_HIT (description not available)....
338818848
2 MEM_LOAD_RETIRED:LLC_MISS (description not available)............
3219718
3 UNHALTED_CORE_CYCLES (description not available).................
7312056865
Event Index
============================================================================================
1: MEM_LOAD_RETIRED:LLC_UNSHARED_HIT 2: MEM_LOAD_RETIRED:LLC_MISS
3: UNHALTED_CORE_CYCLES
Statistics
============================================================================================
Counting domain........................................................
user
Multiplexed............................................................
no
Wall clock time (seconds)..............................................
4.310
----------------------------------------------
Here we can see that the "Wall clock time" output (4.31s) by psprocess
is quite larger than the runtime of cg.A (both in terms of the outputs
of cg.A,2.06s, and time command, about 2.7s.).
Where does other part of time go? What causes the overhead?
And what's the real meaning of the "Wall clock time" here?
Second, in the output xml file of psrun, there is the count of cpu time:
<cputime units="seconds">
<usertime>2.002680</usertime>
<systemtime>0.000010</systemtime>
</cputime>
We can see that this is quite close to the real run time of cg.A.
Why does psprocess not show these valuse?
Will you add this function in upcoming ps-1.0?
Regards,
Jie
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