Re: [PATCH 0/4] Extend migrate_misplaced_page() to support batch migration

[Baolin Wang]

On 8/21/2023 4:41 PM, Huang, Ying wrote:
> Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> writes:
>
> > On 8/21/2023 10:29 AM, Huang, Ying wrote:
> > > Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> writes:
> > >
> > > > Hi,
> > > >
> > > > Currently, on our ARM servers with NUMA enabled, we found the cross-die latency
> > > > is a little larger that will significantly impact the workload's performance.
> > > > So on ARM servers we will rely on the NUMA balancing to avoid the cross-die
> > > > accessing. And I posted a patchset[1] to support speculative numa fault to
> > > > improve the NUMA balancing's performance according to the principle of data
> > > > locality. Moreover, thanks to Huang Ying's patchset[2], which introduced batch
> > > > migration as a way to reduce the cost of TLB flush, and it will also benefit
> > > > the migration of multiple pages all at once during NUMA balancing.
> > > >
> > > > So we plan to continue to support batch migration in do_numa_page() to improve
> > > > the NUMA balancing's performance, but before adding complicated batch migration
> > > > algorithm for NUMA balancing, some cleanup and preparation work need to do firstly,
> > > > which are done in this patch set. In short, this patchset extends the
> > > > migrate_misplaced_page() interface to support batch migration, and no functional
> > > > changes intended.
> > > Will these cleanup benefit anything except batching migration?  If
> > > not,
> >
> > I hope these cleanup can also benefit the compound page's NUMA
> > balancing, which was discussed in the thread[1]. IIUC, for the
> > compound page's NUMA balancing, it is possible that partial pages were
> > successfully migrated, so it is necessary to return the number of
> > pages that were successfully migrated from
> > migrate_misplaced_page(). (But I did not look this in detail yet,
> > please correct me if I missed something, and I will find some time to
> > look this in detail). That is why I think these cleanups are
> > straightforward.
> >
> > Yes, I will post the batch migration patches after more polish and
> > testing, but I think these cleanups are separate and straightforward,
> > so I plan to submit the patches separately.
>
> Then, please state the benefit explicitly in the patch description
> instead of just preparation for batching migration.

Sure, will do. Thanks.