Re: page fault scalability patch V11 [0/7]: overview

Nick Piggin
2004-11-20T02:46:11Z

William Lee Irwin III wrote:
> William Lee Irwin III wrote:
>
>>>Unprivileged triggers for full-tasklist scans are NMI oops material.
>
>
> On Sat, Nov 20, 2004 at 01:25:37PM +1100, Nick Piggin wrote:
>
>>What about pushing the per-thread rss delta back into the global atomic
>>rss counter in each schedule()?
>>Pros:
>>This would take the task exiting problem into its stride as a matter of
>>course.
>>Single atomic read to get rss.
>>Cons:
>>would just be moving the atomic op somewhere else if we don't get
>>many page faults per schedule.
>>Not really nice dependancies.
>>Assumes schedule (not context switch) must occur somewhat regularly.
>>At present this is not true for SCHED_FIFO tasks.
>>Too nasty?
>
>
> This doesn't sound too hot. There's enough accounting that can't be
> done anywhere but schedule(), and this can be done elsewhere. Plus,
> you're moving an already too-frequent operation to a more frequent
> callsite.
>

No, it won't somehow increase the number of atomic rss operations
just because schedule is called more often. The number of ops will
be at _most_ the number of page faults.

But I agree with your overall evaluation of its 'hotness'. Just
another idea. Give this monkey another thousand years at the keys
and he'll come up with the perfect solution :P