From: Greg Smith <greg@2ndquadrant.com>
To: Greg Smith <greg@2ndQuadrant.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Benchmarking a large server
Date: Tue, 10 May 2011 13:50:40 -0400
Message-ID: <4DC97AF0.2050204@2ndquadrant.com> (raw)
In-Reply-To: <4DC8C2B1.1020004@2ndQuadrant.com>
References: <BANLkTikONPZ_7zQNfbyyN4MGBnn5PXHrAg@mail.gmail.com>
<BANLkTikecJCGWH0WyKFiSnC08kmcwS7FqA@mail.gmail.com>
<4DC88793.4000708@emolecules.com>
<4DC88905.8030200@boreham.org>
<0683F5F5A5C7FE419A752A034B4A0B9702B61997@sswchi5pmbx2.peak6.net>
<4DC8C2B1.1020004@2ndQuadrant.com>
Greg Smith wrote:
> On 05/09/2011 11:13 PM, Shaun Thomas wrote:
>> Take a look at /proc/sys/vm/dirty_ratio and
>> /proc/sys/vm/dirty_background_ratio if you have an older Linux
>> system, or /proc/sys/vm/dirty_bytes, and
>> /proc/sys/vm/dirty_background_bytes with a newer one.
>> On older systems for instance, those are set to 40 and 20
>> respectively (recent kernels cut these in half).
>
> 1/4 actually; 10% and 5% starting in kernel 2.6.22. The main sources
> of this on otherwise new servers I see are RedHat Linux RHEL5 systems
> running 2.6.18. But as you say, even the lower defaults of the newer
> kernels can be way too much on a system with lots of RAM.
Ugh...we're both right, sort of. 2.6.22 dropped them to 5/10:
http://kernelnewbies.org/Linux_2_6_22 as I said. But on the new
Scientific Linux 6 box I installed yesterday, they're at 10/20--as you
suggested.
Can't believe I'm going to need a table by kernel version and possibly
distribution to keep this all straight now, what a mess.
--
Greg Smith 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: greg@2ndquadrant.com
Subject: Re: Benchmarking a large server
In-Reply-To: <4DC97AF0.2050204@2ndquadrant.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox