From: Pavel Tatashin <pasha.tatashin@oracle.com>
To: dan.j.williams@intel.com
Cc: Michal Hocko <mhocko@suse.com>,
jack@suse.cz, benh@kernel.crashing.org,
Heiko Carstens <heiko.carstens@de.ibm.com>,
Linux Memory Management List <linux-mm@kvack.org>,
dalias@libc.org, paulus@samba.org, hpa@zytor.com, hch@lst.de,
Yoshinori Sato <ysato@users.sourceforge.jp>,
linux-nvdimm@lists.01.org, x86@kernel.org, willy@infradead.org,
Daniel Jordan <daniel.m.jordan@oracle.com>,
mingo@redhat.com, fenghua.yu@intel.com, jglisse@redhat.com,
tglx@linutronix.de, tony.luck@intel.com,
LKML <linux-kernel@vger.kernel.org>,
mpe@ellerman.id.au, schwidefsky@de.ibm.com,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v2 00/14] mm: Asynchronous + multithreaded memmap init for ZONE_DEVICE
Date: Tue, 17 Jul 2018 10:46:39 -0400 [thread overview]
Message-ID: <CAGM2reacO1HF91yH8OR5w5AdZwPgwfSFfjDNBsHbP66v1rEg=g@mail.gmail.com> (raw)
In-Reply-To: <CAPcyv4jo91jKjwn-M7cOhG=6vJ3c-QCyp0W+T+CtmiKGyZP1ng@mail.gmail.com>
> > Hi Dan,
> >
> > I am worried that this work adds another way to multi-thread struct
> > page initialization without re-use of already existing method. The
> > code is already a mess, and leads to bugs [1] because of the number of
> > different memory layouts, architecture specific quirks, and different
> > struct page initialization methods.
>
> Yes, the lamentations about the complexity of the memory hotplug code
> are known. I didn't think this set made it irretrievably worse, but
> I'm biased and otherwise certainly want to build consensus with other
> mem-hotplug folks.
>
> >
> > So, when DEFERRED_STRUCT_PAGE_INIT is used we initialize struct pages
> > on demand until page_alloc_init_late() is called, and at that time we
> > initialize all the rest of struct pages by calling:
> >
> > page_alloc_init_late()
> > deferred_init_memmap() (a thread per node)
> > deferred_init_pages()
> > __init_single_page()
> >
> > This is because memmap_init_zone() is not multi-threaded. However,
> > this work makes memmap_init_zone() multi-threaded. So, I think we
> > should really be either be using deferred_init_memmap() here, or teach
> > DEFERRED_STRUCT_PAGE_INIT to use new multi-threaded memmap_init_zone()
> > but not both.
>
> I agree it would be good to look at unifying the 2 async
> initialization approaches, however they have distinct constraints. All
> of the ZONE_DEVICE memmap initialization work happens as a hotplug
> event where the deferred_init_memmap() threads have already been torn
> down. For the memory capacities where it takes minutes to initialize
> the memmap it is painful to incur a global flush of all initialization
> work. So, I think that a move to rework deferred_init_memmap() in
> terms of memmap_init_async() is warranted because memmap_init_async()
> avoids a global sync and supports the hotplug case.
>
> Unfortunately, the work to unite these 2 mechanisms is going to be
> 4.20 material, at least for me, since I'm taking an extended leave,
> and there is little time for me to get this in shape for 4.19. I
> wouldn't be opposed to someone judiciously stealing from this set and
> taking a shot at the integration, I likely will not get back to this
> until September.
Hi Dan,
I do not want to hold your work, so if Michal or Andrew are OK with
the general approach of teaching memmap_init_zone() to be async
without re-using deferred_init_memmap() or without changing
deferred_init_memmap() to use the new memmap_init_async() I will
review your patches.
Thank you,
Pavel
>
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next prev parent reply other threads:[~2018-07-17 14:47 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-16 17:00 [PATCH v2 00/14] mm: Asynchronous + multithreaded memmap init for ZONE_DEVICE Dan Williams
2018-07-16 17:00 ` [PATCH v2 01/14] mm: Plumb dev_pagemap instead of vmem_altmap to memmap_init_zone() Dan Williams
2018-07-16 17:00 ` [PATCH v2 02/14] mm: Enable asynchronous __add_pages() and vmemmap_populate_hugepages() Dan Williams
2018-07-16 17:00 ` [PATCH v2 03/14] mm: Teach memmap_init_zone() to initialize ZONE_DEVICE pages Dan Williams
2018-07-16 17:00 ` [PATCH v2 04/14] mm: Multithread ZONE_DEVICE initialization Dan Williams
2018-07-16 17:00 ` [PATCH v2 05/14] mm, memremap: Up-level foreach_order_pgoff() Dan Williams
2018-07-16 21:00 ` Matthew Wilcox
2018-07-16 17:00 ` [PATCH v2 06/14] mm: Allow an external agent to coordinate memmap initialization Dan Williams
2018-07-16 17:00 ` [PATCH v2 07/14] libnvdimm, pmem: Allow a NULL-pfn to ->direct_access() Dan Williams
2018-07-16 17:01 ` [PATCH v2 08/14] tools/testing/nvdimm: " Dan Williams
2018-07-16 17:01 ` [PATCH v2 09/14] s390, dcssblk: " Dan Williams
2018-07-16 17:01 ` [PATCH v2 10/14] filesystem-dax: Do not request a pfn when not required Dan Williams
2018-07-16 17:01 ` [PATCH v2 11/14] filesystem-dax: Make mount time pfn validation a debug check Dan Williams
2018-07-16 17:01 ` [PATCH v2 12/14] libnvdimm, pmem: Initialize the memmap in the background Dan Williams
2018-07-16 17:01 ` [PATCH v2 13/14] device-dax: " Dan Williams
2018-07-16 17:01 ` [PATCH v2 14/14] libnvdimm, namespace: Publish page structure init state / control Dan Williams
2018-07-16 19:12 ` [PATCH v2 00/14] mm: Asynchronous + multithreaded memmap init for ZONE_DEVICE Pavel Tatashin
2018-07-16 20:30 ` Dan Williams
2018-07-17 14:46 ` Pavel Tatashin [this message]
2018-07-17 15:50 ` Michal Hocko
2018-07-17 17:32 ` Dan Williams
2018-07-18 12:05 ` Michal Hocko
2018-07-19 18:41 ` Dave Hansen
2018-07-23 11:09 ` Michal Hocko
2018-07-23 16:15 ` Dave Hansen
2018-07-24 7:29 ` Michal Hocko
2018-09-10 19:06 ` Dan Williams
2018-09-10 19:47 ` Alexander Duyck
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