From: Keith Busch <keith.busch@intel.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>,
linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org,
linux-mm@kvack.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Rafael Wysocki <rafael@kernel.org>,
Dave Hansen <dave.hansen@intel.com>,
Dan Williams <dan.j.williams@intel.com>
Subject: Re: [PATCH 1/7] node: Link memory nodes to their compute nodes
Date: Mon, 19 Nov 2018 08:49:37 -0700 [thread overview]
Message-ID: <20181119154937.GD23062@localhost.localdomain> (raw)
In-Reply-To: <d5c7a267-840b-f253-ef0d-3715b2bcc196@arm.com>
On Mon, Nov 19, 2018 at 08:45:25AM +0530, Anshuman Khandual wrote:
> On 11/17/2018 12:02 AM, Keith Busch wrote:
> > On Thu, Nov 15, 2018 at 12:36:54PM -0800, Matthew Wilcox wrote:
> >> So ... let's imagine a hypothetical system (I've never seen one built like
> >> this, but it doesn't seem too implausible). Connect four CPU sockets in
> >> a square, each of which has some regular DIMMs attached to it. CPU A is
> >> 0 hops to Memory A, one hop to Memory B and Memory C, and two hops from
> >> Memory D (each CPU only has two "QPI" links). Then maybe there's some
> >> special memory extender device attached on the PCIe bus. Now there's
> >> Memory B1 and B2 that's attached to CPU B and it's local to CPU B, but
> >> not as local as Memory B is ... and we'd probably _prefer_ to allocate
> >> memory for CPU A from Memory B1 than from Memory D. But ... *mumble*,
> >> this seems hard.
> >
> > Indeed, that particular example is out of scope for this series. The
> > first objective is to aid a process running in node B's CPUs to allocate
> > memory in B1. Anything that crosses QPI are their own.
>
> This is problematic. Any new kernel API interface should accommodate B2 type
> memory as well from the above example which is on a PCIe bus. Because
> eventually they would be represented as some sort of a NUMA node and then
> applications will have to depend on this sysfs interface for their desired
> memory placement requirements. Unless this interface is thought through for
> B2 type of memory, it might not be extensible in the future.
I'm not sure I understand the concern. The proposal allows linking B
to B2 memory.
next prev parent reply other threads:[~2018-11-19 15:52 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-14 22:49 [PATCH 1/7] node: Link memory nodes to their compute nodes Keith Busch
2018-11-14 22:49 ` [PATCH 2/7] node: Add heterogenous memory performance Keith Busch
2018-11-19 3:35 ` Anshuman Khandual
2018-11-19 15:46 ` Keith Busch
2018-11-22 13:22 ` Anshuman Khandual
2018-11-27 7:00 ` Dan Williams
2018-11-27 17:42 ` Dan Williams
2018-11-27 17:44 ` Keith Busch
2018-11-14 22:49 ` [PATCH 3/7] doc/vm: New documentation for " Keith Busch
2018-11-15 12:59 ` Jonathan Cameron
2018-12-10 16:12 ` Dan Williams
2018-11-20 13:51 ` Mike Rapoport
2018-11-20 15:31 ` Keith Busch
2018-11-14 22:49 ` [PATCH 4/7] node: Add memory caching attributes Keith Busch
2018-11-15 0:40 ` Dave Hansen
2018-11-19 4:14 ` Anshuman Khandual
2018-11-19 23:06 ` Keith Busch
2018-11-22 13:29 ` Anshuman Khandual
2018-11-26 15:14 ` Keith Busch
2018-11-26 19:06 ` Greg Kroah-Hartman
2018-11-26 19:53 ` Keith Busch
2018-11-26 19:06 ` Greg Kroah-Hartman
2018-11-14 22:49 ` [PATCH 5/7] doc/vm: New documentation for memory cache Keith Busch
2018-11-15 0:41 ` Dave Hansen
2018-11-15 13:16 ` Jonathan Cameron
2018-11-20 13:53 ` Mike Rapoport
2018-11-14 22:49 ` [PATCH 6/7] acpi: Create subtable parsing infrastructure Keith Busch
2018-11-19 9:58 ` Rafael J. Wysocki
2018-11-19 18:36 ` Keith Busch
2018-11-14 22:49 ` [PATCH 7/7] acpi/hmat: Parse and report heterogeneous memory Keith Busch
2018-11-15 13:57 ` [PATCH 1/7] node: Link memory nodes to their compute nodes Matthew Wilcox
2018-11-15 14:59 ` Keith Busch
2018-11-15 17:50 ` Dan Williams
2018-11-19 3:04 ` Anshuman Khandual
2018-11-15 20:36 ` Matthew Wilcox
2018-11-16 18:32 ` Keith Busch
2018-11-19 3:15 ` Anshuman Khandual
2018-11-19 15:49 ` Keith Busch [this message]
2018-12-04 15:43 ` Aneesh Kumar K.V
2018-12-04 16:54 ` Keith Busch
2018-11-16 22:55 ` Dan Williams
2018-11-19 2:52 ` Anshuman Khandual
2018-11-19 2:46 ` Anshuman Khandual
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