[bf1942] 64bit linux BF2 performance stats

Steven Hartland killing at multiplay.co.uk
Wed Jul 20 20:18:57 EDT 2005

I dont think the linux scheduler is really NUMA aware. Its quite
a complex problem to solve. I know its something that the BSD
folks are looking at but really hasn't got very far.
tbh if the thread is primarily io / kernel its quite poss the effect
of migration is minimal especially if any data set is small.
NUMA really comes into play in heavily memory access apps.
and Im not sure BF2 comes into the category.

----- Original Message ----- 
From: "James Gurney" <james at globalmegacorp.org>
To: <bf1942 at icculus.org>
Sent: Wednesday, July 20, 2005 11:04 PM
Subject: Re: [bf1942] 64bit linux BF2 performance stats

> On 7/20/2005 3:46 AM, Andreas Fredriksson wrote:
>> The only price you pay for CPU migration of a thread is some
>> added migration overhead in the kernel which amounts to very little
>> time compared to the 10ms (standard) timeslice of most kernels.
> Is that still true for NUMA based systems? I'm a little unclear, but my 
> understanding was that the main advantage of NUMA was dedicated memory 
> per cpu, so migrating from one cpu to the other would lose that 
> advantage. Quoting from the (hugely out of date) Linux NUMA page:
> "On NUMA systems, optimal performance is obtained by locating processes 
> as close to the memory they access as possible.  For most processes, 
> optimal performance is obtained by allocating all memory for the process 
> from the same node, and dispatching the process on processors on that 
> node.  NUMA awareness within the scheduler is necessary in order to 
> support locality of processes to memory - primarily by dispatching a 
> process on the same node through the duration of the procesess' life."
> From that, I'm concluding that locking at least the most memory 
> intensive threads to one cpu would be of benefit on a NUMA system, but 
> perhaps I'm misunderstanding the overall picture..

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