Messages in this thread | | | Subject | Re: [PATCH] low-latency zap_page_range() | From | Robert Love <> | Date | 29 Aug 2002 17:12:11 -0400 |
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On Thu, 2002-08-29 at 17:00, Andrew Morton wrote:
> That's an interesting point. page_table_lock is one of those locks > which is occasionally held for ages, and frequently held for a short > time.
Since latency is a direct function of lock held times in the preemptible kernel, and I am seeing disgusting zap_page_range() latencies, the lock is held a long time.
So we know it is held forever and a day... but is there contention?
> But I don't recall seeing nasty page_table_lock spintimes on > anyone's lockmeter reports, so we can leave it as-is for now.
I do not recall seeing this either and I have not done my own tests.
Personally, I would love to rip out the "cond_resched_lock()" and just do
spin_unlock(); spin_lock();
and be done with it. This gives automatic preemption support and the SMP benefit. Preemption being an "automatic" consequence of improved locking was always my selling point (albeit, this is a gross example of improving the locking, but it gets the job done).
But, the current implementation was more palatable to you and Linus when I first posted this, and that counts for something.
Robert Love
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