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

[Baoquan He <bhe@redhat.com>]

On 04/24/23 at 11:22am, Lorenzo Stoakes wrote:
> 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).

Thanks for CC. 

Yes, I am very interested in this topic, have read it from the beginning.
Unfortunately, I can't attend LSF/MM this year because of some reasons.
I look forward to learning the decision or conclusion of the sessin, and
reviewing Uladzislau's RFC or formal patchset later.  Wish the session a
great success, and you guys a pleasant meeting and discussion.

Thanks
Baoquan