This is the mail archive of the
systemtap@sourceware.org
mailing list for the systemtap project.
overhead testing results of systemtap/LKET
- From: "Gui,Jian" <guij at cn dot ibm dot com>
- To: systemtap at sources dot redhat dot com
- Date: Tue, 25 Jul 2006 18:19:22 +0800
- Subject: overhead testing results of systemtap/LKET
Hi, we've tested the overhead of systemtap/LKET with some benchmarks
on a ppc64 machine.
It shows the overhead of systemtap/LKET is acceptable generally.
But it will also cause significant overhead for some benchmark of
special behavior, e.g. dbench. Dbench calls kill() in a very high
frequency to check whether a task is complete, thus leads to a high
overhead.
We categorized the event hooks into five groups in the testing:
grp1 - syscall.entry, process
grp2 - syscall.return, process
grp3 - iosyscall, ioscheduler, scsi, aio, process
grp4 - tskdispatch, pagefault, netdev, process
grp5 - syscall.entry, syscall.return, process
All the results are
(score1 - score2)/score2 * 100%, where:
score1: the benchmark score when probed by systemtap
score2: the benchmark score without probing
dbench (<3% is noise)
--------------------
grp1 -14.4%
grp2 -33.1%
grp3 -7.92%
grp4 -13.6%
grp5 -43.3%
specjbb (<3% is noise)
---------------------
grp 1 -0.87%
grp 2 -0.67%
grp 4 +0.47%
grp 5 +0.05%
tiobench (<3% is noise)
----------------------
grp1 sequential reads +1.45%
sequential writes -6.98%
random reads +0.57%
random writes -2.11%
grp2 sequential reads +0.11%
sequential writes -5.81%
random reads +0.03%
random writes -2.11%
grp3 sequential reads +1.42%
sequential writes -6.98%
random reads +0.51%
random writes -2.11%
grp4 sequential reads +1.38%
sequential writes -5.81%
random reads +0.60%
random writes -2.11%
grp5 sequential reads +0.22%
sequential writes -8.14%
random reads -0.10%
random writes -1.05%
Rawiobench (<3% is noise)
------------------------
grp1 sequential aioread() 0%
sequential aiowrite() 0%
random aioread() 0%
random aiowrite() 0%
grp2 sequential aioread() 0%
sequential aiowrite() 0%
random aioread() 0%
random aiowrite() -0.82%
grp3 sequential aioread() 0%
sequential aiowrite() 0%
random aioread() 0%
random aiowrite() 0%
grp4 sequential aioread() 0%
sequential aiowrite() 0%
random aioread() +0.79%
random aiowrite() -0.82%
grp5 sequential aioread() 0%
sequential aiowrite() -6.41%
random aioread() +0.79%
random aiowrite() 0%
Test environment:
Machine: Open Power 720/ 8 cpus/ 2 cores/ 6GB RAM (tiobench use 1G)
Software: RHEL4-U3GA/ 2.6.17.2/ systemtap-20060718/ elfutils-0.122-0.4