linux-kernel - Re: [driver-core PATCH v8 0/9] Add NUMA aware async

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Message-ID: <20181210233507.GK28501@garbanzo.do-not-panic.com>
Date:   Mon, 10 Dec 2018 15:35:07 -0800
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Alexander Duyck <alexander.h.duyck@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        linux-nvdimm@...ts.01.org, tj@...nel.org,
        akpm@...ux-foundation.org, linux-pm@...r.kernel.org,
        jiangshanlai@...il.com, rafael@...nel.org, len.brown@...el.com,
        pavel@....cz, zwisler@...nel.org, dan.j.williams@...el.com,
        dave.jiang@...el.com, bvanassche@....org
Subject: Re: [driver-core PATCH v8 0/9] Add NUMA aware async_schedule calls

On Mon, Dec 10, 2018 at 03:25:04PM -0800, Alexander Duyck wrote:
> On Mon, 2018-12-10 at 11:22 -0800, Luis Chamberlain wrote:
> > On Wed, Dec 05, 2018 at 09:25:13AM -0800, Alexander Duyck wrote:
> > > This patch set provides functionality that will help to improve the
> > > locality of the async_schedule calls used to provide deferred
> > > initialization.
> > > 
> > > This patch set originally started out focused on just the one call to
> > > async_schedule_domain in the nvdimm tree that was being used to defer the
> > > device_add call however after doing some digging I realized the scope of
> > > this was much broader than I had originally planned. As such I went
> > > through and reworked the underlying infrastructure down to replacing the
> > > queue_work call itself with a function of my own and opted to try and
> > > provide a NUMA aware solution that would work for a broader audience.
> > > 
> > > In addition I have added several tweaks and/or clean-ups to the front of the
> > > patch set. Patches 1 through 4 address a number of issues that actually were
> > > causing the existing async_schedule calls to not show the performance that
> > > they could due to either not scaling on a per device basis, or due to issues
> > > that could result in a potential deadlock. For example, patch 4 addresses the
> > > fact that we were calling async_schedule once per driver instead of once
> > > per device, and as a result we would have still ended up with devices
> > > being probed on a non-local node without addressing this first.
> > 
> > No tests were added. Again, I think it would be good to add test
> > cases to showcase the old mechanisms, illustrate the new, and ensure
> > we don't regress both now and also help us ensure we don't regress
> > moving forward.
> > 
> > This is all too critical of a path for the kernel, and these changes
> > are rather instrusive. I'd readlly like to see test code for it now
> > rather than later.
> > 
> >   Luis
> 
> Sorry about that. I was more focused on the rewrite of patch 2 and
> overlooked the comment about lib/test_kmod.c.
> 
> I'll look into it and see if I can squeeze it in for v9.

Superb!

  Luis