[sugar] Re: [OLPC-devel] pygtk performance issue
Wed Sep 6 10:10:12 EDT 2006
Marco Pesenti Gritti wrote:
> Mitch Bradley wrote:
>> The processor on OLPC is inherently slower than the processors that
>> are used in modern laptops. To get ultra low power you have to
>> sacrifice something. It seems unlikely that we would be able to hide
>> that inherent speed differential by a kernel change. In the short
>> term, I don't know of any planned hardware changes that would
>> substantially increase the performance of file system activity on USB
> Ok, this is the kind of feedback I was looking for. What about the
> internal flash? Is it going to be substantially faster than USB drives?
I wouldn't count on it being enough faster to make a huge difference in
the case you are investigating. I expect that the process is mostly
CPU-bound. Somebody correct me if I'm wrong, but the kernel buffer
cache is probably preventing most of those failed opens from having to
re-access the USB hardware.
You could test that easily; just create/mount a tmpfs (RAM-resident)
directory and try your script on it.
> I believe that "work smarter" is a key component of the OLPC plan. It
> looks like you have found some "low-hanging fruit" that is ripe for
> the picking. Improving pygtk to start up in a less "brute force" way
> would benefit not only OLPC, but everybody else as well.
> Definitely. But it's also important to prioritize the work. The whole
> point of this mail is to figure out how critical the "opening a bunch
> of files" issues is going to be on the final hardware/kernel.
The current hardware and kernel is a reasonable model for the speed of
the final system. We'll certainly make some improvements to the core
performance of the low-level system, but it won't be an order of
magnitude*. So order of magnitude speedups will have to come from
avoiding unnecessary work, rather than depending on the system to be so
fast that waste doesn't matter.
*I am, however, confident that we can make huge improvements in the
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