The sample time decreases when I run high cpu utilization job.

Hi All,

I use oprofile to try profile the database server's (MySQL) performance.

I start with this command before I start my test:
sudo nohup operf --pid `pgrep mysqld` &
All the tests will be run for 150s.

When the CPU utilization is low, the sample number seems reasonable.
However, when the CPU utilization is very high, more than 100%, the sample
number decreases dramatically.

*Because the sample numbers change a lot in these tests. So I'm not sure if
I can still believe the results I got in the high CPU utilization case. I
think the sampling should be done in a fix time interval. So the sampling
number should be similar.*

The total sample numbers are 42417612 samples and 1226 samples, for 70% CPU
utilization and 100% CPU utilization.

*Is my understanding right? Or what's the right way to use oprofile in the
high CPU utilization case?*

Looking forward to your reply.

Thanks,
Tim
---------------------------------------------------------------------------------
Below are the symbols results.
70% cpu utilization:
samples  %        image name               symbol name
2340974   5.5390  mysqld                   MYSQLparse(THD*)
1024614   2.4243  mysqld                   rec_get_offsets_func(unsigned
char const*, dict_index_t c
onst*, unsigned long*, unsigned long, mem_block_info_t**)
610260    1.4439  mysqld                   lex_one_token(YYSTYPE*, THD*)
[clone .constprop.119]

>100% cpu utilization:

samples  %        image name               symbol name
63        4.8951  libc-2.22.so             __strcmp_sse2_unaligned
60        4.6620  mysqld                   fill_schema_collation(THD*,
TABLE_LIST*, Item*)
44        3.4188  mysqld                   my_strnncollsp_utf8
29        2.2533  libc-2.22.so             __memcpy_avx_unaligned

------------------------------------------------------------------------------
Transform Data into Opportunity.
Accelerate data analysis in your applications with
Intel Data Analytics Acceleration Library.
Click to learn more.
http://pubads.g.doubleclick.net/gampad/clk?id=278785111&iu=/4140

_______________________________________________
oprofile-list mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/oprofile-list