On 28.12.2011 14:03, Tatsuo Ishii wrote:
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/8292.1314641...@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.
Here is new patch using TAS_SPIN(), created by Manabu Ori from IBM
Japan. Also this patch deal with older Power architectures which do
not have "hint" argument of lwarx opcode.
According to him, the patch resulted in much better performance stock
git head.
Impressive results.
config/c-compiler.m4 doesn't seem like the right place for the configure
test. Would there be any harm in setting the lwarx hint always; what
would happen on older ppc processors that don't support it?
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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