hyperthreading performance with dbt-2 on 2.6.0-test11

[markw@osdl.org]

Hello, I have some data with hyperthreading I wanted to share.

I've seen about a 15% performance decrease in performance on a 4-way
Xeon system when I enable hyperthreading for my DBT-2 workload.  I also
gave Ingo's test11-C1 patch that someone pointed me to a try and only
saw a 12% decrease. Has anyone found this to be common with any specific
workloads?

I'm not really sure what to look for, but I do see some changes in the
readprofile data, which I've copied in part below.  It appears that the
count of schedule, __make_request, and try_to_wake_up are the only
functions at the top of the profile that are significantly different.
The links I have posted also have pointers to oprofile data as well as
annotated assembly source output, if that interests anyone.  If I can
provide any other details, let me know.

For the test with no hyperthreading
(http://developer.osdl.org/markw/dbt2-pgsql/258/):

8199701 poll_idle                                141374.1552
159442 schedule                                  93.5144
133488 __copy_from_user_ll                      1059.4286
128589 __copy_to_user_ll                        1071.5750
 73209 DAC960_LP_InterruptHandler               367.8844
 51885 __make_request                            36.0062
 35614 try_to_wake_up                            55.6469


For the test with hyperthreading
(http://developer.osdl.org/markw/dbt2-pgsql/253/):

20893773 poll_idle                                360237.4655
351988 schedule                                 206.4446
155826 __copy_from_user_ll                      1038.8400
152346 __copy_to_user_ll                        1269.5500
 90983 DAC960_LP_InterruptHandler               457.2010
 86936 try_to_wake_up                           135.8375
 70122 __make_request                            48.6620


For the test with hyperthreading and Ingo's patch
(http://developer.osdl.org/markw/dbt2-pgsql/260/):

20544823 poll_idle                                354221.0862
520575 schedule                                 231.6756
159609 __copy_from_user_ll                      1266.7381
153279 __copy_to_user_ll                        1277.3250
139321 try_to_wake_up                           221.4960
 92447 DAC960_LP_InterruptHandler               464.5578
 72162 __make_request                            50.0777


-- 
Mark Wong - - markw@osdl.org
Open Source Development Lab Inc - A non-profit corporation
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