Re: Benchmarking a large server

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(at)2ndQuadrant(dot)com Baltimore, MD
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