Skip site navigation (1) Skip section navigation (2)

Re: Hyperthreading (was: Two identical systems, radically different performance)

From: Shaun Thomas <sthomas(at)optionshouse(dot)com>
To: Craig James <cjames(at)emolecules(dot)com>
Cc: <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Hyperthreading (was: Two identical systems, radically different performance)
Date: 2012-10-10 12:52:37
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
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


See for terms and conditions related to this email

In response to


pgsql-performance by date

Next:From: Shaun ThomasDate: 2012-10-10 13:09:56
Subject: Re: shared_buffers/effective_cache_size on 96GB server
Previous:From: Fran├žois BeausoleilDate: 2012-10-10 12:38:28
Subject: Re: Ways to speed up ts_rank

Privacy Policy | About PostgreSQL
Copyright © 1996-2017 The PostgreSQL Global Development Group