Messages in this thread |  | | Subject | Re: [PATCH] Significant performace improvements on reiserfs systems | From | Robert Love <> | Date | 20 Sep 2001 23:14:21 -0400 |
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On Thu, 2001-09-20 at 21:20, Andrew Morton wrote: > This may not be practical. > > Take, for example, zap_page_range(). It simply has a lot > of work to do, and it does it inside a spinlock. By doing > it in a tight loop, it's optimal. > > There is no way to speed this function up by two or three orders > of magnitude. (Well, there is: don't take the lock at all if > the mm isn't shared, but this is merely an example. There are > other instances).
Agreed, but...
> It seems that for a preemptive kernel to be successful, we need > to globally alter the kernel so that it never holds locks for > more than 500 microseconds. Which is what the conditional_schedule() > (aka cooperative multitasking :)) patches do. > > It seems that there are no magic bullets, and low latency will > forever have a global impact on kernel design, unless a way is > found to reschedule with locks held. I recall that a large > part of the MontaVista patch involved turning spinlocks into > semaphores, yes? That would seem to be the way to go.
This would be the situation that solved the problem with little complaint, huh?
-- Robert M. Love rml at ufl.edu rml at tech9.net
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