Re: Performance on PowerQuicc8280 linux based

["aldo lab" <aldo.lab@gmail.com>]

If I remove the changes I'm not available to reach the previous
result, and to perform the test I use an external traffic generator (
Smartbit) and this has an hight precision.
So the problem in some way should be tied to cache but I don't know
what I can try.I blocked some critical function (in term of cpu
cycles)  in istruction cache but I didn't obtained a good result
Let me know if you have some idea

Thanks
Aldo


On 11/15/06, Dan Malek <dan@embeddedalley.com> wrote:
>
> On Nov 15, 2006, at 11:21 AM, Jeff Mock wrote:
>
> > I'm no big help, but the problem might be TLB related instead of cache
> > related.  The performance of embedded PPCs with small TLBs requiring
> > software assist for TLB misses can be performance sensitive to TLB
> > misses.
>
> The 82xx is fully cache coherent and has BATs for
> mapping the kernel space.  This is not a PPC with
> a small TLB, but rather one of the most efficient.
> The TLBs are not an issue,  and I doubt the caches
> are as well.
>
> I don't know what kind of test is used to measure this
> performance, but the first thing you must always scrutinize
> are your testing methods and procedures.  Just using
> a user application to measure network performance
> enables a large number of variables that must be
> properly understood and controlled.  Some other
> thread could have switched in and stolen CPU cycles,
> you could have some sampling rate and time
> measurement hysteresis due to buffering,
> you need to find and control such things.
>
> Can you "undo" the changes and get the old
> results?  That's the first thing I would verify,
> and then verify the results are repeatable.
> If that's the case, I'd carefully try to understand
> what this "unrelated" change really affects
> in terms of using CPU cycles.
>
> Thanks.
>
>        -- Dan
>
>