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Solaris Eye for the Linux Guy… Part II (oprofile, Dtrace, and Oracle Event Trace)

Proper tool for the job

My grandfather used to say to me: “Use the proper tool for the job”.  This is important to keep in mind when faced with performance issues.  When I am faced with performance problems in Oracle, I typically start at a high level with AWR reports or Enterprise Manager to get a high level understanding of the workload.   To drill down further, the next step is to use Oracle “10046 event” tracing.  Cary Millsap created a methodology around event tracing called “Method-R” which shows how to focus in on the source of a performance problem by analyzing the components that contribute to response time.   These are all fine places to start to analyze performance problems from the “user” or “application” point of view.  But what happens if the OS is in peril?

If you are experiencing high system time or strange application behavior, it is likely time to drill deeper with OS based tools.  I mentioned in my last post , “prstat” is the “top” equivalent for Solaris.  “prstat” is the best place to start to see how processes are running on Solaris, but at some point you may need to drill down deeper to gain a better understanding of the problem.

With Linux “oprofile” allows you to sample the kernel and user code to build a profile of how the system and applications are behaving.  This is an incredibly useful tool, but it doesn’t exist on Solaris.  Luckily, there is something that is arguably better – Dtrace.

Solaris Dtrace(1m) / Linux “oprofile”

Dtrace was developed for the release of Solaris 10 by kernel engineers as a way to better debug and monitor Solaris.  Unlike “oprofile”, Dtrace is an really an environment that involves writing code in “D” to make use of the numerous amounts of probe data that exist.  Dtrace is really powerful, but it does require some heavy lifting to get started.  This is where the “Dtrace Toolkit” comes in handy.

The “Dtrace Toolkit” is a set of scripts that server as a starting point for those interested in using Dtrace.  Also included in the “Dtrace Toolkit” are some real clever utilities.  My two favorite utilities for Dtrace are the “hotkernel” and “hotuser” scripts.  These scripts analyze either the kernel or a user “PID” to show which routines are most used.  This can be extremely useful when diagnosing performance problems that extend beyond the V$ tables or Oracle “10046 event trace” data.

To illustrate the use of these utilities, I have included output from a benchmark that shows how these might be used.


root@apl5-1> ./hotkernel
Sampling... Hit Ctrl-C to end.
FUNCTION                                                COUNT   PCNT
nxge`nxge_check_10g_link                                    1   0.0%
genunix`ioctl                                               1   0.0%
genunix`fop_read                                         5730   2.1%
genunix`kstrgetmsg                                       6091   2.2%
unix`utl0                                                7058   2.6%
FJSV,SPARC64-VII`cpu_halt_cpu                            7220   2.6%
FJSV,SPARC64-VII`copyout                                 9340   3.4%
ip`tcp_fuse_output                                      12637   4.6%
unix`_resume_from_idle                                  12922   4.7%
unix`disp_getwork                                       18864   6.8%
unix`mutex_enter                                        34033  12.3%


root@apl5-1> ./hotuser -p 12626
Sampling... Hit Ctrl-C to end.
FUNCTION                                                COUNT   PCNT
oracle`kxsInitExecutionHeap                                 1   0.0%
oracle`0x10b319ad0                                          1   0.0%
oracle`kews_pls_jvm_event_resume_i                          1   0.0%
oracle`0x10b319ac8                                          1   0.0%
oracle`kghfrh                                               1   0.0%
oracle`opiptc                                               1   0.0%
oracle`qertbFetchByRowID                                   91   1.0%
oracle`kghalf                                              94   1.1%`memcpy                                      102   1.2%
oracle`opikndf2                                           105   1.2%
oracle`kpofcr                                             113   1.3%
oracle`opiodr                                             120   1.4%
oracle`kslwtectx                                          120   1.4%
oracle`kslwt_update_stats_int                             126   1.4%
oracle`opitsk                                             126   1.4%
oracle`ksupucg                                            151   1.7%
oracle`nsbasic_brc                                        153   1.7%
oracle`kdxbrs1                                            187   2.1%
oracle`kdxlrs2                                            192   2.2%
oracle`kews_sqlcol_end                                    194   2.2%
oracle`opifch2                                            212   2.4%
oracle`opiexe                                             250   2.8%
oracle`skgslcas                                           265   3.0%`memset                                      416   4.7%
oracle`kcbgtcr                                            826   9.4%

You can begin to see how Dtrace can be useful to see the effect of the workload on Solaris and profile the user application – in this case an Oracle shadow process.  But this is just the beginning.  If you are so inclined, Dtrace can be used to correlate all sorts of performance data both inside the kernel and application.

Filed under: Linux, Oracle, Solaris Tagged: 10046, Dtrace, linux, oprofile, Oracle, performance, prstat, sar, Solaris, top