Re: [Lsf-pc] LSFMMBPF proposal [MM]: Eliminate vmap/vmalloc lock contention

[Lorenzo Stoakes <lstoakes@gmail.com>]

On Mon, Apr 24, 2023 at 12:08:22PM +0200, Uladzislau Rezki wrote:
> On Mon, Apr 24, 2023 at 10:55:20AM +0200, Michal Hocko wrote:
> > On Mon 24-04-23 09:44:00, Uladzislau Rezki wrote:
> > > On Fri, Apr 21, 2023 at 02:03:43PM +0200, Michal Hocko wrote:
> > > > On Tue 28-02-23 17:42:43, Uladzislau Rezki wrote:
> > > > > Hello, LSF.
> > > > >
> > > > > Title: Introduce a per-cpu-vmap-cache to eliminate a vmap lock contention
> > > > >
> > > > > Description:
> > > > >  Currently the vmap code is not scaled to number of CPU cores in a system
> > > > >  because a global vmap space is protected by a single spinlock. Such approach
> > > > >  has a clear bottleneck if many CPUs simultaneously access to one resource.
> > > > >
> > > > >  In this talk i would like to describe a drawback, show some data related
> > > > >  to contentions and places where those occur in a code. Apart of that i
> > > > >  would like to share ideas how to eliminate it providing a few approaches
> > > > >  and compare them.
> > > >
> > > > It's been some time since you brough this up. Has there been any
> > > > progress on the topic? Do you still find it important to discuss it at
> > > > LSFMM?
> > > >
> > > The idea about sequence was/is:
> > >
> > > 1) Give an overview on the proposal;
> > > 2) Submit patches to address the problem;
> > > 3) Start a discussion over lkml with people who are interested in it;
> > > 4) Send out a complete solution.
> >
> > Thanks for the clarification. The usual LSFMM format is strongly
> > discussion focused. Long presentations are usually discouraged and they
> > should only introduce people to the underlying problem to kick of a
> > discussion.
> >
> I have not posted yet any RFC and have not kicked it yet. Though people
> are aware the problem.
>
> >
> > That being said, IMO it would be helpful to have some material on the
> > mailing list before any discussion could be productive.
> >
> This is what i have so far:
>
> wget ftp://vps418301.ovh.net/incoming/Fix_a_vmalloc_lock_contention_in_SMP_env.pdf
>
> I can, of course, move it forward over lkml only. If you are fully
> booked or there other reason then please just withdraw my proposal
> from your conference.

For what it's worth I'm definitely interested in attending this session if
it goes ahead. I am sure Baoquan, if he's attending LSF/MM, would be too! (cc'd).