linux-kernel - Re: [PATCH v2 00/14] mm: Asynchronous + multithreaded memmap init for ZONE

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Message-ID: <CAKgT0UeN1Et7+5ddGW3-rD8M5o9MJ5xr755f2T7szBX=PEczRQ@mail.gmail.com>
Date:   Mon, 10 Sep 2018 12:47:55 -0700
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     dan.j.williams@...el.com
Cc:     mhocko@...nel.org, Dave Hansen <dave.hansen@...el.com>,
        Pavel Tatashin <pasha.tatashin@...cle.com>, dalias@...c.org,
        jack@...e.cz, Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        linux-mm <linux-mm@...ck.org>, Paul Mackerras <paulus@...ba.org>,
        Peter Anvin <hpa@...or.com>, ysato@...rs.sourceforge.jp,
        linux-nvdimm@...ts.01.org,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Ingo Molnar <mingo@...hat.com>, fenghua.yu@...el.com,
        jglisse@...hat.com, Thomas Gleixner <tglx@...utronix.de>,
        Tony Luck <tony.luck@...el.com>,
        LKML <linux-kernel@...r.kernel.org>, mpe@...erman.id.au,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>,
        "Duyck, Alexander H" <alexander.h.duyck@...el.com>
Subject: Re: [PATCH v2 00/14] mm: Asynchronous + multithreaded memmap init for ZONE_DEVICE

On Mon, Sep 10, 2018 at 12:06 PM Dan Williams <dan.j.williams@...el.com> wrote:
>
> [ adding Alex ]
>
> On Tue, Jul 24, 2018 at 12:29 AM, Michal Hocko <mhocko@...nel.org> wrote:
> > On Mon 23-07-18 09:15:32, Dave Hansen wrote:
> >> On 07/23/2018 04:09 AM, Michal Hocko wrote:
> >> > On Thu 19-07-18 11:41:10, Dave Hansen wrote:
> >> >> Are you looking for the actual end-user reports?  This was more of a
> >> >> case of the customer plugging in some persistent memory DIMMs, noticing
> >> >> the boot delta and calling the folks who sold them the DIMMs (Intel).
> >> > But this doesn't sound like something to rush a solution for in the
> >> > upcoming merge windown, does it?
> >>
> >> No, we should not rush it.  We'll try to rework it properly.
> >
> > Thanks a lot Dave! I definitely do not mean to block this at all. I just
> > really do not like to have the code even more cluttered than we have
> > now.
>
> Hi Michal,
>
> I'm back from vacation. I owe you an apology I was entirely too
> prickly on this thread, and the vacation cool-off-time was much
> needed.
>
> I come back to see that Alex has found a trove of low hanging fruit to
> speed up ZONE_DEVICE init and ditch most of the complication I was
> pushing. I'll let him chime in on the direction he wants to take this.

The basic plan I have for now will basically replace the entire set-up
with just 2 patches that would build on the 2 patches I had submitted
earlier.

One is a patch to the libnvdimm code to make it so that the probe
routine NUMA aware similar to what is done in pci_call_probe. All of
the async bits necessary were already contained in the libnvdimm code
anyway. Ideally I need to probably look at following up with adding
some NUMA awareness to the async_schedule_domain function.

The second is actually pretty simple. Instead of moving the setting of
the pgmap into memmap_init_zone we instead create a new function to
take care of setting the pgmap and include the functionality from
memmap_init_zone. The boundary between what is initialized and what
isn't is where we start replacing the LRU list pointers with pgmap and
hmm_data.

I might try to send them out as an RFC later today to get everyone's thoughts.

Thanks.

- Alex