Re: [PATCH] mm/vmstat: Reduce zone lock hold time when reading /proc/pagetypeinfo

[Feng Tang]

On Wed, Oct 23, 2019 at 11:01:04PM +0800, Waiman Long wrote:
> On 10/23/19 10:48 AM, Qian Cai wrote:
> >>> this still isn't a bulletproof fix.  Maybe just terminate the list
> >>> walk if freecount reaches 1024.  Would anyone really care?
> >>>
> >>> Sigh.  I wonder if anyone really uses this thing for anything
> >>> important.  Can we just remove it all?
> >>>
> >> Removing it will be a breakage of kernel API.
> > Who cares about breaking this part of the API that essentially nobody will use
> > this file?
> >
> There are certainly tools that use /proc/pagetypeinfo and this is how
> the problem is found. I am not against removing it, but we have to be
> careful and deprecate it in way that minimize user impact.

We have been using the /proc/pagetypeinfo for debugging, mainly for
client platforms like phones/tablets. We met problems like very slow
system response or OOM things, and many of them could be related with
memory pressure or fragmentation issues, where monitoring /proc/pagetypeinfo
will be very useful for debugging.

So I think Michal's idea to change it to 0400 is a good idea.

Thanks,
Feng

 
> Cheers,
> Longman
> 
>