Re: aio stress panic on 2.6.11-mm1

From: Andi Kleen
Date: Wed Mar 09 2005 - 06:26:30 EST

Arjan van de Ven <arjan@xxxxxxxxxxxxx> writes:

> On Wed, 2005-03-09 at 16:34 +0530, Suparna Bhattacharya wrote:
>> Any sense of how costly it is to use spin_lock_irq's vs spin_lock
>> (across different architectures) ? Isn't rwsem used very widely ?
> oh also rwsems aren't used all that much simply because they are quite
> more expensive than regular semaphores, so that you need a HUGE bias in
> reader/writer ratio to make it even worth it...

I agree. I think in fact once Christopher L's lockless page fault fast path
goes in it would be a good idea to reevaluate if mmap_sem should
be really a rwsem and possibly change it back to a normal semaphore
that perhaps gets dropped only on a page cache miss.

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