Subject: Re: Page allocator bottleneck

From: Aaron Lu <[email-masked]>
Date: Fri, 27 Apr 2018 16:45:58 +0800

On Mon, Apr 23, 2018 at 09:10:33PM +0800, Aaron Lu wrote:
> On Mon, Apr 23, 2018 at 11:54:57AM +0300, Tariq Toukan wrote:
> > Hi,
> > 
> > I ran my tests with your patches.
> > Initial BW numbers are significantly higher than I documented back then in
> > this mail-thread.
> > For example, in driver #2 (see original mail thread), with 6 rings, I now
> > get 92Gbps (slightly less than linerate) in comparison to 64Gbps back then.
> > 
> > However, there were many kernel changes since then, I need to isolate your
> > changes. I am not sure I can finish this today, but I will surely get to it
> > next week after I'm back from vacation.
> > 
> > Still, when I increase the scale (more rings, i.e. more cpus), I see that
> > queued_spin_lock_slowpath gets to 60%+ cpu. Still high, but lower than it
> > used to be.
> 
> I wonder if it is on allocation path or free path?

Just FYI, I have pushed two more commits on top of the branch.
They should improve free path zone lock contention for MIGRATE_UNMOVABLE
pages(most kernel code alloc such pages), you may consider apply them if
free path contention is a problem.