Re: Buffer Requests Trace - Mailing list pgsql-hackers

From Jeff Janes
Subject Re: Buffer Requests Trace
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Msg-id CAMkU=1z5n6FZVcb_7bHAU8QXAmsE=-Vv8x3CAOkVN3XrjrSRuw@mail.gmail.com
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In response to Re: Buffer Requests Trace  (Lucas Lersch <lucaslersch@gmail.com>)
Responses Re: Buffer Requests Trace
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On Wed, Oct 15, 2014 at 6:22 AM, Lucas Lersch <lucaslersch@gmail.com> wrote:
So is it a possible normal behavior that running tpcc for 10min only access 50% of the database? Furthermore, is there a guideline of parameters for tpcc (# of warehouses, execution time, operations weight)?


I'm not familiar with your benchmarking tool.  With the one I am most familiar with, pgbench, if you run it against a database which is too big to fit in memory, it can take a very long time to touch each page once, because the constant random disk reads makes it run very slowly.  Maybe that is something to consider here--how many transactions were actually executed during your 10 min run?

Also, the tool might build tables that are only used under certain run options.  Perhaps you just aren't choosing the options which invoke usage of those tables.  Since you have the trace data, it should be pretty easy to count how many distinct blocks are accessed from each relation, and compare that to the size of the relations to see which relations are unused or lightly used.

Cheers,

Jeff

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