Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 22 May 2024 14:27:32 -0700 | Subject | Re: [PATCH v18 17/17] x86/resctrl: Update documentation with Sub-NUMA cluster changes | From | Reinette Chatre <> |
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Hi Tony,
On 5/15/2024 3:23 PM, Tony Luck wrote: > *** This patch needs updating for new files for monitoring *** > > With Sub-NUMA Cluster mode enabled the scope of monitoring resources is > per-NODE instead of per-L3 cache. Suffixes of directories with "L3" in > their name refer to Sub-NUMA nodes instead of L3 cache ids.
Out of date?
> > Users should be aware that SNC mode also affects the amount of L3 cache > available for allocation within each SNC node. > > Signed-off-by: Tony Luck <tony.luck@intel.com> > --- > Documentation/arch/x86/resctrl.rst | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst > index 627e23869bca..401f6bfb4a3c 100644 > --- a/Documentation/arch/x86/resctrl.rst > +++ b/Documentation/arch/x86/resctrl.rst > @@ -375,6 +375,10 @@ When monitoring is enabled all MON groups will also contain: > all tasks in the group. In CTRL_MON groups these files provide > the sum for all tasks in the CTRL_MON group and all tasks in > MON groups. Please see example section for more details on usage. > + On systems with Sub-NUMA (SNC) cluster enabled there are extra
"Sub-NUMA (SNC) cluster" -> "Sub-NUMA Cluster (SNC)"?
> + directories for each node (located within the "mon_L3_XX" directory > + for the L3 cache they occupy). These are named "mon_sub_L3_YY" > + where "YY" is the node number. > > "mon_hw_id": > Available only with debug option. The identifier used by hardware > @@ -484,6 +488,19 @@ if non-contiguous 1s value is supported. On a system with a 20-bit mask > each bit represents 5% of the capacity of the cache. You could partition > the cache into four equal parts with masks: 0x1f, 0x3e0, 0x7c00, 0xf8000. > > +Notes on Sub-NUMA Cluster mode > +============================== > +When SNC mode is enabled, Linux may load balance tasks between Sub-NUMA > +nodes much more readily than between regular NUMA nodes since the CPUs > +on Sub-NUMA nodes share the same L3 cache and the system may report > +the NUMA distance between Sub-NUMA nodes with a lower value than used > +for regular NUMA nodes. > +The top-level monitoring files in each "mon_L3_XX" directory provide > +the sum of data across all SNC nodes sharing an L3 cache instance. > +Users who bind tasks to the CPUs of a specific Sub-NUMA node can read > +the "llc_occupancy", "mbm_total_bytes", and "mbm_local_bytes" in the > +"mon_sub_L3_YY" directories to get node local data. > + > Memory bandwidth Allocation and monitoring > ========================================== >
Reinette
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