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SubjectRe: [PATCH] low-latency zap_page_range()
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


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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