[nylug-talk] LOWMEM vs. HIGHMEM performance advantage?

[jh]

Peter C. Norton wrote:
> On Thu, Apr 17, 2008 at 10:30:55AM -0400, jh wrote:
>> I have an application that appears to slow down once it starts using 
>> about 900 megs of memory.
>>
>> Interestingly, from dmesg:
>>
>> [42949372.960000] 1150MB HIGHMEM available.
>> [42949372.960000] 896MB LOWMEM available.
>>
>> Is HIGHMEM slower, or are there circumstances or kernel configs such 
>> that I could be seeing such a slowdown once memory usage goes above a 
>> certain level?
> 
> Are you using a 2.4 kernel? I thought the split was moved much closer
> to the 4gb line in 2.6.

Nope:

Linux rerender02 2.6.17-12-server #2 SMP Tue Feb 12 01:19:08 UTC 2008 
i686 GNU/Linux

 From a recentish version of Ubuntu server.

jh

> 
> http://www.linux.org/docs/ldp/howto/IO-Perf-HOWTO/overview.html
> 
> -Peter
> 
>