On 11/29/23 18:34, Tony Luck wrote: > 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. > > 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@xxxxxxxxx> > Reviewed-by: Peter Newman <peternewman@xxxxxxxxxx> > Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx> > Reviewed-by: Shaopeng Tan <tan.shaopeng@xxxxxxxxxxxxxx> > Tested-by: Shaopeng Tan <tan.shaopeng@xxxxxxxxxxxxxx> > --- > Documentation/arch/x86/resctrl.rst | 25 +++++++++++++++++++++---- > 1 file changed, 21 insertions(+), 4 deletions(-) > > diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst > index a6279df64a9d..49ff789db1d8 100644 > --- a/Documentation/arch/x86/resctrl.rst > +++ b/Documentation/arch/x86/resctrl.rst > @@ -366,10 +366,10 @@ When control is enabled all CTRL_MON groups will also contain: > When monitoring is enabled all MON groups will also contain: > > "mon_data": > - This contains a set of files organized by L3 domain and by > - RDT event. E.g. on a system with two L3 domains there will > - be subdirectories "mon_L3_00" and "mon_L3_01". Each of these > - directories have one file per event (e.g. "llc_occupancy", > + This contains a set of files organized by L3 domain or by NUMA > + node (depending on whether Sub-NUMA Cluster (SNC) mode is disabled > + or enabled respectively) and by RDT event. Each of these > + directories has one file per event (e.g. "llc_occupancy", > "mbm_total_bytes", and "mbm_local_bytes"). In a MON group these > files provide a read out of the current value of the event for > all tasks in the group. In CTRL_MON groups these files provide > @@ -478,6 +478,23 @@ 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 enabled, Linux Thanks Babu > +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. Users who do not bind tasks to the CPUs of a > +specific Sub-NUMA node must read the "llc_occupancy", "mbm_total_bytes", > +and "mbm_local_bytes" for all Sub-NUMA nodes where the tasks may execute > +to get the full view of traffic for which the tasks were the source. > + > +The cache allocation feature still provides the same number of > +bits in a mask to control allocation into the L3 cache, but each > +of those ways has its capacity reduced because the cache is divided > +between the SNC nodes. The values reported in the resctrl > +"size" files are adjusted accordingly. > + > Memory bandwidth Allocation and monitoring > ========================================== > -- Thanks Babu Moger
