Re: [PATCH 2/3] mm, meminit: Recalculate pcpu batch and high limits after init completes

[Mel Gorman]

On Fri, Oct 18, 2019 at 06:40:24PM -0700, Andrew Morton wrote:
> On Fri, 18 Oct 2019 15:09:59 +0100 Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote:
> 
> > > > Cc: stable@xxxxxxxxxxxxxxx # v4.15+
> > > 
> > > Hmm, are you sure about 4.15? Doesn't this go all the way down to
> > > deferred initialization? I do not see any recent changes on when
> > > setup_per_cpu_pageset is called.
> > > 
> > 
> > No, I'm not 100% sure. It looks like this was always an issue from the
> > code but did not happen on at least one 4.12-based distribution kernel for
> > reasons that are non-obvious. Either way, the tag should have been "v4.1+"
> 
> I could mark
> 
> mm-pcp-share-common-code-between-memory-hotplug-and-percpu-sysctl-handler.patch
> mm-meminit-recalculate-pcpu-batch-and-high-limits-after-init-completes.patch
> 
> as Cc: <stable@xxxxxxxxxxxxxxx>	[4.1+]
> 

That would be fine.

> But for backporting purposes it's a bit cumbersome that [2/3] is the
> important patch.  I think I'll switch the ordering so that
> mm-meminit-recalculate-pcpu-batch-and-high-limits-after-init-completes.patch
> is the first patch and the other two can be queued for 5.5-rc1, OK?
> 

It might be easier to simply collapse patch 1 and 2 together. They were
only split to make the review easier and to avoid two relatively big
changes in one patch.

> Also, is a Reported-by:Matt appropriate here?
> 

I don't object but I'm not actually sure who reported this first. I think
it was Thomas who talked to Boris about an EPYC performance issue, who
talked to Matt thinking it might be a scheduler issue who identified it
was my problem :P

-- 
Mel Gorman
SUSE Labs