BFS vs. mainline scheduler benchmarks and measurements

BFS vs. mainline scheduler benchmarks and measurements

And no I don't think Fedoras smolt data is any good here. Fedora users are technical people and are unlikely to run really old hardware like my sisters for example.

That's all fine and i have a Fedora Core 6 box too on old hardware - which is very old.

I wouldnt upgrade the kernel on it though - and non-technical users would do that even less likely. Software and hardware is in a single unit and for similar reasons it is hard to upgrade hardware is it difficult to upgrade software as well. Yes, you pick up security fixes, etc. - but otherwise main components like the kernel tend to be cast into stone at install time. (And no, if you are reading this on LWN.Net then your box probably does not qualify ;-)

Which means that most of the 4 years old systems have a 4 years old distribution on them, with a 4 years old kernel. That kernel was developed 5 years ago and any deep scheduler decisions were done 6 years ago or even later.

So yes, i agree that the upgrade treadmill has to stop eventually, but _I_ cannot make it stop - i just observe reality and adopt to it. I see what users do, i see what vendors do and i try to develop the kernel in the best possible technical way, matching those externalities.

What i'm seeing right now as the scheduler and as the x86 co-maintainer is that the hardware side shows no signs of slowing down and that users who are willing to install new kernels show eagerness to buy shiny new hardware. Quads yesterday, six-cores today, opto-cores in a year or two.

Most of the new kernel installs goes to fresh new systems, so that's an important focus of the upstream kernel - and of any distribution maker. That is the space where we _can_ do something realistically and if we did something else we'd be ignoring our users.

I could certainly be wrong about all that in some subtle (or not so subtle) way - but right now the fact is that most of the bugreports i get against development code we release is done on relatively new hardware.

That is natural to a certain degree - new hardware triggers new, previously unknown limitations and bottlenecks, and new hardware has its own problems too that gets mixed into kernel problems, etc. Old hardware is also already settled into its workload so there's little reason to upgrade an old, working box in general. There's also the built-in human excitement factor that shiny new hardware triggers on a genetic level ;-)

There's an easy way out though: please report bugs on old hardware and make old hardware count. The mainline kernel can only recognize and consider people who are willing to engage. The upstream kernel process is a fundamentally auto-tuning and auto-correcting mechanism and it is mainly influenced by people willing to improve code.