On 10/09/2012 06:30 PM, Craig James wrote:
ra:8192 walb:1M ra:256 walb:1M ra:256 walb:256kB
---------------- ---------------- -----------------
-c -t Run1 Run2 Run3 Run4 Run5 Run6 Run7 Run8 Run9
40 2500 4261 3722 4243 9286 9240 5712 9310 8530 8872
50 2000 4138 4399 3865 9213 9351 9578 8011 7651 8362
I think I speak for more than a few people here when I say: wat.
About the only thing I can ask, is: did you make these tests fair? And
by fair, I mean:
echo 3 > /proc/sys/vm/drop_caches
pg_ctl -D /your/pg/dir restart
Between every test to make sure shared buffers and the OS inode cache
was empty before the start of each test? If you're using that bash-style
for-loop you attached earlier, probably not. Still though, I don't think
that would account for this much variance between having read-ahead at
8M as opposed to 256kb.
My head hurts.
--
Shaun Thomas
OptionsHouse | 141 W. Jackson Blvd. | Suite 500 | Chicago IL, 60604
312-444-8534
sthomas@xxxxxxxxxxxxxxxx
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