Messages in this thread | | | Date | Wed, 7 May 2003 19:40:27 +0200 | From | Jörn Engel <> | Subject | Re: top stack (l)users for 2.5.69 |
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On Wed, 7 May 2003 10:18:29 -0700, Davide Libenzi wrote: > On Wed, 7 May 2003, [iso-8859-1] Jörn Engel wrote: > > > It also matters if people writing applications for embedded systems > > have a fetish for many threads. 1000 threads, each eating 8k memory > > for pure existance (no actual work done yet), do put some memory > > pressure on small machines. Yes, it would be possible to educate those > > people, but changing kernel code is more fun and less work. > > I'm afraid I do not agree with both your sentences. Changing a *working > kernel* code is definitely not much fun and not really less work if your > target is the per-cpu kernel stack. You'll completely lose kernel > preemption and this is really bad since many paths inside the kernel are > easily preemptable. The design and the code of the kernel will become more > complex (and slow) and even people that are correctly programming it are > going to pay the price. No thanks, I'd say screw you thread maniacs ...
I'm not sure if I got you wrong, or vice versa. Either way, some definitions first. Process Stack == the traditional per-process kernel stack Interrupt Stack == a dedicated per-CPU stack for interrupts only CPU Stack == all kernel data on a per-CPU stack
Not for anything would I want a CPU Stack. At first thought, this is impossible, but in reality it is just ugly beyond anything I could bear.
An Interrupt Stack is a very good thing. I know PPC machines with 125 Interrupt lines (3 for cascading) that could theoretically all happen at once. That alone demands for a stack size well above 8k and having this per process is just a bad design. But that is another issue.
The real Process Stack without the interrupt overhead should not need to be bigger than 4k. It currently is for all platforms I know about, s390 has even 16k. This is the point of my regular allyesconfig compilations and postings.
Do you still disagree? Then I must have misread your mail.
Jörn
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