lkml.org 
[lkml]   [2022]   [May]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: RFC: Memory Tiering Kernel Interfaces (v2)
On Thu, May 12, 2022 at 12:12 AM Aneesh Kumar K V
<aneesh.kumar@linux.ibm.com> wrote:
>
> On 5/12/22 12:33 PM, ying.huang@intel.com wrote:
> > On Wed, 2022-05-11 at 23:22 -0700, Wei Xu wrote:
> >> Sysfs Interfaces
> >> ================
> >>
> >> * /sys/devices/system/memtier/memtierN/nodelist
> >>
> >> where N = 0, 1, 2 (the kernel supports only 3 tiers for now).
> >>
> >> Format: node_list
> >>
> >> Read-only. When read, list the memory nodes in the specified tier.
> >>
> >> Tier 0 is the highest tier, while tier 2 is the lowest tier.
> >>
> >> The absolute value of a tier id number has no specific meaning.
> >> What matters is the relative order of the tier id numbers.
> >>
> >> When a memory tier has no nodes, the kernel can hide its memtier
> >> sysfs files.
> >>
> >> * /sys/devices/system/node/nodeN/memtier
> >>
> >> where N = 0, 1, ...
> >>
> >> Format: int or empty
> >>
> >> When read, list the memory tier that the node belongs to. Its value
> >> is empty for a CPU-only NUMA node.
> >>
> >> When written, the kernel moves the node into the specified memory
> >> tier if the move is allowed. The tier assignment of all other nodes
> >> are not affected.
> >>
> >> Initially, we can make this interface read-only.
> >
> > It seems that "/sys/devices/system/node/nodeN/memtier" has all
> > information we needed. Do we really need
> > "/sys/devices/system/memtier/memtierN/nodelist"?
> >
> > That can be gotten via a simple shell command line,
> >
> > $ grep . /sys/devices/system/node/nodeN/memtier | sort -n -k 2 -t ':'
> >
>
> It will be really useful to fetch the memory tier node list in an easy
> fashion rather than reading multiple sysfs directories. If we don't have
> other attributes for memorytier, we could keep
> "/sys/devices/system/memtier/memtierN" a NUMA node list there by
> avoiding /sys/devices/system/memtier/memtierN/nodelist
>
> -aneesh

It is harder to implement memtierN as just a file and doesn't follow
the existing sysfs pattern, either. Besides, it is extensible to have
memtierN as a directory.

\
 
 \ /
  Last update: 2022-05-12 09:24    [W:0.155 / U:0.080 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site