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| author |   Prarit Bhargava <prarit@redhat.com> | 2014-10-23 14:22:12 -0400 |
|---|---|---|
| committer |   Bjorn Helgaas <bhelgaas@google.com> | 2014-11-06 15:10:06 -0700 |
| commit | 63692df103e9c76b26c382ce8079283b7df9a99a (patch) | |
| tree | 677204f229cd7ad3dcf072d8d7eb44ce01018e9e /Documentation/ABI | |
| parent | Linux 3.18-rc1 (diff) | |
| download | linux-dev-63692df103e9c76b26c382ce8079283b7df9a99a.tar.xz linux-dev-63692df103e9c76b26c382ce8079283b7df9a99a.zip | |
PCI: Allow numa_node override via sysfs
NUMA systems with ACPI normally describe the physical topology via _PXM
methods. But many BIOSes don't implement _PXM, which leaves the kernel
with no way to discover the device topology, which reduces performance
because we can't put memory and processes close to the device.
The NUMA node of a PCI device is already exported in the sysfs "numa_node"
file. Make that file writable so users can workaround the lack of _PXM
methods in the BIOS. For example:
echo 3 > /sys/devices/pci0000:ff/0000:03:1f.3/numa_node
sets the node for PCI device 0000:03:1f.3.
Writing the file emits a FW_BUG warning to encourage users to request
firmware updates. It also taints the kernel with TAINT_FIRMWARE_WORKAROUND
because overriding the node incorrectly can cause performance issues.
[bhelgaas: changelog, documentation text]
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Myron Stowe <mstowe@redhat.com>
CC: Alexander Ducyk <alexander.h.duyck@redhat.com>
CC: Jiang Liu <jiang.liu@linux.intel.com>
Diffstat (limited to 'Documentation/ABI')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-pci | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci index ee6c04036492..b3bc50f650ee 100644 --- a/Documentation/ABI/testing/sysfs-bus-pci +++ b/Documentation/ABI/testing/sysfs-bus-pci @@ -281,3 +281,16 @@ Description: opt-out of driver binding using a driver_override name such as "none". Only a single driver may be specified in the override, there is no support for parsing delimiters. + +What: /sys/bus/pci/devices/.../numa_node +Date: Oct 2014 +Contact: Prarit Bhargava <prarit@redhat.com> +Description: + This file contains the NUMA node to which the PCI device is + attached, or -1 if the node is unknown. The initial value + comes from an ACPI _PXM method or a similar firmware + source. If that is missing or incorrect, this file can be + written to override the node. In that case, please report + a firmware bug to the system vendor. Writing to this file + taints the kernel with TAINT_FIRMWARE_WORKAROUND, which + reduces the supportability of your system. |