>> With help from IBM Japan Ltd. we did some tests on a larger IBM
>> machine than Tom Lane has used for his
>> test(http://archives.postgresql.org/message-id/8292.1314641721@sss.pgh.pa.us).
>> In his case it was IBM 8406-71Y, which has 8 physical cores and
>> 4SMT(32 threadings). Ours is IBM Power 750 Express, which has 32
>> physical cores and 4SMT(128 threadings), 256GB RAM.
>>
>> The test method was same as the one in the article above. The
>> differences are OS(RHEL 6.1), gcc version (4.4.5) and shared buffer
>> size(8GB).
>>
>> We tested 3 methods to enhance spin lock contention:
>>
>> 1) Add "hint" parameter to lwarx op which is usable POWER6 or later
>> architecure.
>>
>> 2) Add non-locked test in TAS()
>>
>> 3) #1 + #2
>>
>> We saw small performance enhancement with #1, larger one with #2 and
>> even better with #1+#2.
>
> Hmm, so you added the non-locked test in TAS()? Did you try adding it
> just to TAS_SPIN()? On Itanium, I found that it was slightly better
> to do it only in TAS_SPIN() - i.e. in the contended case.
The actual test was performed by one of our engineers in my company
(Toshihiro Kitagawa). I think the answer to your question is yes, but
let me talk to him to make it sure.
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp