From: | Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp> |
---|---|
To: | Vadim Mikheev <vadim(at)krs(dot)ru> |
Cc: | t-ishii(at)sra(dot)co(dot)jp, Stupor Genius <stuporg(at)erols(dot)com>, Pgsql-Hackers <pgsql-hackers(at)postgreSQL(dot)org> |
Subject: | Re: [HACKERS] 8K block limit |
Date: | 1999-02-18 03:33:51 |
Message-ID: | 199902180333.MAA06625@srapc451.sra.co.jp |
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Thread: | |
Lists: | pgsql-hackers |
>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
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