Re: Sequential Scan Read-Ahead - Mailing list pgsql-hackers

From Curt Sampson
Subject Re: Sequential Scan Read-Ahead
Date
Msg-id Pine.NEB.4.43.0204251805000.3111-100000@angelic.cynic.net
Whole thread Raw
In response to Re: Sequential Scan Read-Ahead  (Curt Sampson <cjs@cynic.net>)
List pgsql-hackers
On Thu, 25 Apr 2002, Curt Sampson wrote:

> Here's the ratio table again, with another column comparing the
> aggregate number of requests per second for one process and four
> processes:
>

Just for interest, I ran this again with 20 processes working
simultaneously. I did six runs at each blockread size and summed
the tps for each process to find the aggregate number of reads per
second during the test. I dropped the higest and the lowest ones,
and averaged the rest. Here's the new table:
    1 proc    4 procs    20 procs
   1 block    310    440    260   2 blocks    262    401    481   4 blocks    199    346    354   8 blocks    132
260   250   16 blocks     66    113    116
 

I'm not sure at all why performance gets so much *worse* with a lot of
contention on the 1K reads. This could have something to with NetBSD, or
its buffer cache, or my laptop's crappy little disk drive....

Or maybe I'm just running out of CPU.

cjs
-- 
Curt Sampson  <cjs@cynic.net>   +81 90 7737 2974   http://www.netbsd.org   Don't you know, in this new Dark Age, we're
alllight.  --XTC
 



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