From: Mike Rapoport <rppt@linux.ibm.com>
To: Keith Busch <keith.busch@intel.com>
Cc: 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 3/7] doc/vm: New documentation for memory performance
Date: Tue, 20 Nov 2018 14:51:50 +0100 [thread overview]
Message-ID: <20181120135149.GA24627@rapoport-lnx> (raw)
In-Reply-To: <20181114224921.12123-4-keith.busch@intel.com>
Hi,
Sorry if I'm jumping too late.
On Wed, Nov 14, 2018 at 03:49:16PM -0700, Keith Busch wrote:
> Platforms may provide system memory where some physical address ranges
> perform differently than others. These heterogeneous memory attributes are
> common to the node that provides the memory and exported by the kernel.
>
> Add new documentation providing a brief overview of such systems and
> the attributes the kernel makes available to aid applications wishing
> to query this information.
>
> Signed-off-by: Keith Busch <keith.busch@intel.com>
> ---
> Documentation/vm/numaperf.rst | 71 +++++++++++++++++++++++++++++++++++++++++++
As this document describes user-space interfaces it belongs to
Documentation/admin-guide/mm.
> 1 file changed, 71 insertions(+)
> create mode 100644 Documentation/vm/numaperf.rst
>
> diff --git a/Documentation/vm/numaperf.rst b/Documentation/vm/numaperf.rst
> new file mode 100644
> index 000000000000..5a3ecaff5474
> --- /dev/null
> +++ b/Documentation/vm/numaperf.rst
> @@ -0,0 +1,71 @@
> +.. _numaperf:
> +
> +================
> +NUMA Performance
> +================
> +
> +Some platforms may have multiple types of memory attached to a single
> +CPU. These disparate memory ranges share some characteristics, such as
> +CPU cache coherence, but may have different performance. For example,
> +different media types and buses affect bandwidth and latency.
> +
> +A system supporting such heterogeneous memory groups each memory type
> +under different "nodes" based on similar CPU locality and performance
> +characteristics. Some memory may share the same node as a CPU, and
> +others are provided as memory-only nodes. While memory only nodes do not
> +provide CPUs, they may still be local to one or more compute nodes. The
> +following diagram shows one such example of two compute noes with local
> +memory and a memory only node for each of compute node:
> +
> + +------------------+ +------------------+
> + | Compute Node 0 +-----+ Compute Node 1 |
> + | Local Node0 Mem | | Local Node1 Mem |
> + +--------+---------+ +--------+---------+
> + | |
> + +--------+---------+ +--------+---------+
> + | Slower Node2 Mem | | Slower Node3 Mem |
> + +------------------+ +--------+---------+
> +
> +A "memory initiator" is a node containing one or more devices such as
> +CPUs or separate memory I/O devices that can initiate memory requests. A
> +"memory target" is a node containing one or more CPU-accessible physical
> +address ranges.
> +
> +When multiple memory initiators exist, accessing the same memory
> +target may not perform the same as each other. The highest performing
> +initiator to a given target is considered to be one of that target's
> +local initiators.
> +
> +To aid applications matching memory targets with their initiators,
> +the kernel provide symlinks to each other like the following example::
> +
> + # ls -l /sys/devices/system/node/nodeX/initiator*
> + /sys/devices/system/node/nodeX/targetY -> ../nodeY
> +
> + # ls -l /sys/devices/system/node/nodeY/target*
> + /sys/devices/system/node/nodeY/initiatorX -> ../nodeX
> +
> +Applications may wish to consider which node they want their memory to
> +be allocated from based on the nodes performance characteristics. If
> +the system provides these attributes, the kernel exports them under the
> +node sysfs hierarchy by appending the initiator_access directory under
> +the node as follows::
> +
> + /sys/devices/system/node/nodeY/initiator_access/
> +
> +The kernel does not provide performance attributes for non-local memory
> +initiators. The performance characteristics the kernel provides for
> +the local initiators are exported are as follows::
> +
> + # tree /sys/devices/system/node/nodeY/initiator_access
> + /sys/devices/system/node/nodeY/initiator_access
> + |-- read_bandwidth
> + |-- read_latency
> + |-- write_bandwidth
> + `-- write_latency
> +
> +The bandwidth attributes are provided in MiB/second.
> +
> +The latency attributes are provided in nanoseconds.
> +
> +See also: https://www.uefi.org/sites/default/files/resources/ACPI_6_2.pdf
> --
> 2.14.4
>
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2018-11-20 13:52 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 [this message]
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
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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