Re: [HACKERS] 8K block limit

>Tatsuo Ishii wrote:
>>
>> But modern Unixes have read/write ahead i/o if it seems a sequential
>> access, don't they. I did some testing on my LinuxPPC box.
>>
>> 0. create table t2(i int,c char(4000));
>> 1. time psql -c "copy t2 from '/tmp/aaa'" test
>> (aaa has 5120 records and this will create 20MB table)
>> 2. time psql -c "select count(*) from t2" test
>> 3. total time of the regression test
>>
>> o result of testing 1
>>
>> 8K: 0.02user 0.04system 3:26.20elapsed
>> 32K: 0.03user 0.06system 0:48.25elapsed
>>
>> 32K is 4 times faster than 8k!
>>
>> o result of testing 2
>>
>> 8K: 0.02user 0.04system 6:00.31elapsed
>> 32K: 0.04user 0.02system 1:02.13elapsed
>>
>> 32K is neary 6 times faster than 8k!
>
>Did you use the same -B for 8K and 32K ?
>You should use 4x buffers in 8K case!

Ok. This time I started postmaster as 'postmaster -S -i -B 256'.

test1:
0.03user 0.02system 3:21.65elapsed

test2:
0.01user 0.08system 5:30.94elapsed

a little bit faster, but no significant difference?
--
Tatsuo Ishii