Re: [PATCH] mm: Free per cpu pages async to shorten program exit time

[David Hildenbrand]

On 11.10.21 11:28, Michal Hocko wrote:
> On Fri 08-10-21 10:17:50, David Hildenbrand wrote:
> > On 08.10.21 08:39, ultrachin@xxxxxxx wrote:
> > > From: chen xiaoguang <xiaoggchen@xxxxxxxxxxx>
> > >
> > > The exit time is long when program allocated big memory and
> > > the most time consuming part is free memory which takes 99.9%
> > > of the total exit time. By using async free we can save 25% of
> > > exit time.
> > >
> > > Signed-off-by: chen xiaoguang <xiaoggchen@xxxxxxxxxxx>
> > > Signed-off-by: zeng jingxiang <linuszeng@xxxxxxxxxxx>
> > > Signed-off-by: lu yihui <yihuilu@xxxxxxxxxxx>
> >
> > I recently discussed with Claudio if it would be possible to tear down the
> > process MM deferred, because for some use cases (secure/encrypted
> > virtualization, very large mmaps) tearing down the page tables is already
> > the much more expensive operation.
> >
> > There is mmdrop_async(), and I wondered if one could reuse that concept when
> > tearing down a process -- I didn't look into feasibility, however, so it's
> > just some very rough idea.
>
> This is not a new problem. Large process tear down can take ages. The
> primary road block has been accounting. This lot of work has to be
> accounted to the proper domain (e.g. cpu cgroup). 

In general, yes. For some setups where admins don't care about that 
accounting (e.g., enabled via some magic toggle for large VMs), I guess 
this accounting isn't the major roadblock, correct?

--
Thanks,

David / dhildenb