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From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org,
	pavel.tatashin@microsoft.com, dave.jiang@intel.com,
	linux-kernel@vger.kernel.org, willy@infradead.org,
	davem@davemloft.net, yi.z.zhang@linux.intel.com,
	khalid.aziz@oracle.com, rppt@linux.vnet.ibm.com, vbabka@suse.cz,
	sparclinux@vger.kernel.org, dan.j.williams@intel.com,
	ldufour@linux.vnet.ibm.com, mgorman@techsingularity.net,
	mingo@kernel.org, kirill.shutemov@linux.intel.com
Subject: Re: [mm PATCH v3 4/6] mm: Move hot-plug specific memory init into separate functions and optimize
Date: Wed, 24 Oct 2018 10:35:09 -0700	[thread overview]
Message-ID: <15bf78bdadd282b0587097d49cc39d0d7b662736.camel@linux.intel.com> (raw)
In-Reply-To: <20181024152742.GJ18839@dhcp22.suse.cz>

On Wed, 2018-10-24 at 17:27 +0200, Michal Hocko wrote:
> On Wed 24-10-18 08:08:41, Alexander Duyck wrote:
> > On Wed, 2018-10-24 at 14:36 +0200, Michal Hocko wrote:
> > > On Wed 17-10-18 08:26:20, Alexander Duyck wrote:
> > > [...]
> > > > With that said I am also wondering if a possible solution to
> > > > the complaints you had would be to look at just exporting the
> > > > __init_pageblock function later and moving the call to
> > > > memmap_init_zone_device out to the memremap or hotplug code
> > > > when Dan gets the refactoring for HMM and memremap all sorted
> > > > out.
> > > 
> > > Why cannot we simply provide a constructor for each page by the
> > > caller if there are special requirements? we currently have
> > > alt_map
> > > to do struct page allocation but nothing really prevents to make
> > > it
> > > more generic and control both allocation and initialization
> > > whatever
> > > suits a specific usecase. I really do not want make special cases
> > > here and there.
> > 
> > The advantage to the current __init_pageblock function is that we
> > end up constructing everything we are going to write outside of the
> > main loop and then are focused only on init.
> 
> But we do really want move_pfn_range_to_zone to provide a usable pfn
> range without any additional tweaks. If there are potential
> optimizations to be done there then let's do it but please do not try
> to micro optimize to the point that the interface doesn't make any
> sense anymore.

The actual difference between the two setups is not all that great.
From the sound of things the ultimate difference between the
ZONE_DEVICE pages and regular pages is the pgmap and if we want the
reserved bit set or not.

What I am providing with __init_pageblock at this point is a function
that is flexible enough for us to be able to do either one and then
just expose a different front end on it for the specific type of page
we have to initialize. It works for regular hotplug, ZONE_DEVICE, and
deferred memory initialization. The way I view it is that this funciton
is a high performance multi-tasker, not something that is micro-
optimized for any one specific function.

Thanks.

- Alex




  reply	other threads:[~2018-10-24 17:35 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-15 20:26 [mm PATCH v3 0/6] Deferred page init improvements Alexander Duyck
2018-10-15 20:26 ` [mm PATCH v3 1/6] mm: Use mm_zero_struct_page from SPARC on all 64b architectures Alexander Duyck
2018-10-16 19:01   ` Pavel Tatashin
2018-10-17  7:30     ` Mike Rapoport
2018-10-17 14:52       ` Alexander Duyck
2018-10-17  8:47   ` Michal Hocko
2018-10-17 15:07     ` Alexander Duyck
2018-10-17 15:12       ` Pavel Tatashin
2018-10-17 15:40         ` David Laight
2018-10-17 16:31           ` Alexander Duyck
2018-10-17 17:08             ` Pavel Tatashin
2018-10-17 16:34       ` Michal Hocko
2018-10-15 20:27 ` [mm PATCH v3 2/6] mm: Drop meminit_pfn_in_nid as it is redundant Alexander Duyck
2018-10-16 20:33   ` Pavel Tatashin
2018-10-16 20:49     ` Alexander Duyck
2018-10-16 21:06       ` Pavel Tatashin
2018-10-17  9:04   ` Michal Hocko
2018-10-15 20:27 ` [mm PATCH v3 3/6] mm: Use memblock/zone specific iterator for handling deferred page init Alexander Duyck
2018-10-17  9:11   ` Michal Hocko
2018-10-17 15:17     ` Alexander Duyck
2018-10-17 16:42   ` Mike Rapoport
2018-10-15 20:27 ` [mm PATCH v3 4/6] mm: Move hot-plug specific memory init into separate functions and optimize Alexander Duyck
2018-10-17  9:18   ` Michal Hocko
2018-10-17 15:26     ` Alexander Duyck
2018-10-24 12:36       ` Michal Hocko
2018-10-24 15:08         ` Alexander Duyck
2018-10-24 15:27           ` Michal Hocko
2018-10-24 17:35             ` Alexander Duyck [this message]
2018-10-25 12:41               ` Michal Hocko
2018-10-15 20:27 ` [mm PATCH v3 5/6] mm: Use common iterator for deferred_init_pages and deferred_free_pages Alexander Duyck
2018-10-15 20:27 ` [mm PATCH v3 6/6] mm: Add reserved flag setting to set_page_links Alexander Duyck

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