Re: [PATCH] low-latency zap_page_range()

[Andrew Morton]

Robert Love wrote:
> 
> ...
> unless we
> wanted to unconditionally drop the locks and let preempt just do the
> right thing and also reduce SMP lock contention in the SMP case.

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.

I suspect that yes, voluntarily popping the lock during the long holdtimes
will allow other CPUs to get on with stuff, and will provide efficiency
increases.  (It's a pretty lame way of doing that though).

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.