Re: Software prefetching considered harmful

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

> Yeah, over the past 10 years we have been suffering from an increasing level of 
> blindness in the area of x86 performance analysis. Our old tools gradually 
> deteriorated, the hardware got smarter and more parallel and it was harder and 
> harder to see what happens. The 32-bit/64-bit split did not help us stay 
> focused either. I think i warned about this 4-5 years ago at a KS.
> 
> This has improved meanwhile, we now have better tools (*wink* :) and have a 
> good performance monitoring model (*wink* :) and people are again looking at 
> the fine details and i think we now have a good chance to speed up the kernel 
> again and keep it fast - and not just on PowerPC which has its envied Olympus 
> of performance gods! :-)

Hehe, right. I agree completely.

> Watching out for performance is a fundamentally critical mass thing: for a long 
> time it seems a Sisyphean task with little progress, then it just happens very 
> quickly.

I used to pay a lot more attention to performance myself than I do
nowadays, and that is definitely not a good thing. Mostly blame being
swamped with other things but still something I need to remedy in the
near future.

Cheers,
Ben.