Re: [RFC] - Some notions that I would like comments on

(no name) ((no email))
11 Jul 1999 10:53:32 -0400


>>>>> "Jeff" == Jeff Dike <jdike@karaya.com> writes:
> Making idle threads earn their living
> This involves finding parallelism in the kernel and getting an otherwise idle
> processor to handle one of the parallel chunks of work.

Hopeless. The cost of inter-CPU communication is way too high to try
to share such fine-grained tasks.

> Compressive paging
> Before writing a page out to swap, compress it.

Keeps coming back every once in a while. Has already been tried in a few
cases, and it has some definite advantages in a few cases. But it also has
some nasty difficulties. Sadly every experiment I know of ended up stopping
as soon as some code worked and showed little improvement.

> Speculative I/O

Usually called ~asynchronous I/O".

> IPC through page remapping

Slow. Only worth it if the message is big enough (last time I heard, the
cut-over point was around 8KB).

> Runaway process detection

Excellent way to bloat the kernel with code that catches about 1% of the
problematic cases, which happen to be the least annoying cases (your runaway
processes will simply eat up some of your CPU time, but will have a very low
priority, so it doesn't slow down the machine too much, is trivial to kill,
...).

Stefan

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