[PATCH] um: clean up mm creation

[Johannes Berg]

On Fri, 2023-09-22 at 21:08 +0100, Anton Ivanov wrote:
> On 22/09/2023 20:41, Johannes Berg wrote:
> > On Fri, 2023-09-22 at 14:41 +0100, Anton Ivanov wrote:
> > > 
> > > It is nearly twice slower than the current approach on a find /usr -type f -exec cat {} > /dev/null \;
> > > 
> > 
> > Btw, I cannot reproduce that at all - seems about the same in my tests?
> > 
> > Is there anything special in your setup?
> > 
> > Or maybe it's because I'm using hostfs? But not sure why that would
> > matter.
> 
> I am using a ubd with ext4 sitting on an nfs server. The host, however, 
> has more than enough memory to cache all of it, so it is pretty much 
> like reading off a ramdisk as it is fully cached.
> 
> It is quite clear in that case.
> 

Did you have your preempt patch applied also, btw? Because I was working
off that now.

But even with PREEMPT turned off, I see basically no difference in such
a benchmark. I was running only over /usr/bin/ because otherwise it's
just too much time on my system overall, but there's basically no
difference in the 4x4 matrix of

 - preempt off / preempt voluntary
 - with / without my patch

johannes