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SubjectRe: [patch] remove the BKL (Big Kernel Lock), this time for real
On Fri, 17 Sep 2004 08:43:21 +0200, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Bill Huey <bhuey@lnxw.com> wrote:
>
> > Judging from how the Linux code is done and the numbers I get from
> > Bill Irwin in casual conversation, the Linux SMP approach is clearly
> > the right track at this time with it's hand honed per-CPU awareness of
> > things. The only serious problem that spinlocks have as they aren't
> > preemptable, which is what Ingo is trying to fix.
>
> a clarification: note that the current BKL is a special case. No way do
> i suggest that the BKS is the proper model for any SMP implementation.
> It is a narrow special-case because it wraps historic UP-only kernel
> code.
>
> our primary multiprocessing primitives are still the following 4:
> lockless data structures, RCU, spinlocks and mutexes. (reverse ordered
> by level of parallelism.) The BKS is basically a fifth method, a special
> type of semaphore that i'd never want to be seen used by any new SMP
> code. It is completely local to sched.c.
>
> Ingo

I coded a IPC system before use atomic add + share memory.
It works very well (fast) on 4 CPU SMP system, since it doesn't use
any locking API at all. Very good for resource allocation for
SMP. I implemented speciall malloc/free use by ISR, different
prority process
completely without any lock. Negative side, it use more memory.


--
-Tony
Having a lot of fun with Xilinx Virtex Pro II reconfigurable HW + ppc + Linux
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