In the resctrl subsystem's Sub-NUMA Cluster (SNC) mode, the rdt_mon_domain
structure representing a NUMA node relies on the cacheinfo interface
(rdt_mon_domain::ci) to store L3 cache information (e.g., shared_cpu_map)
for monitoring. The L3 cache information of a SNC NUMA node determines
which domains are summed for the "top level" L3-scoped events.
rdt_mon_domain::ci is initialized using the first online CPU of a NUMA
node. When this CPU goes offline, its shared_cpu_map is cleared to contain
only the offline CPU itself. Subsequently, attempting to read counters
via smp_call_on_cpu(offline_cpu) fails (and error ignored), returning
zero values for "top-level events" without any error indication.
Replace the cacheinfo references in struct rdt_mon_domain and struct
rmid_read with the cacheinfo ID (a unique identifier for the L3 cache).
rdt_domain_hdr::cpu_mask contains the online CPUs associated with that
domain. When reading "top-level events", select a CPU from
rdt_domain_hdr::cpu_mask and utilize its L3 shared_cpu_map to determine
valid CPUs for reading RMID counter via the MSR interface.
Considering all CPUs associated with the L3 cache improves the chances
of picking a housekeeping CPU on which the counter reading work can be
queued, avoiding an unnecessary IPI.
Fixes: 328ea68874 ("x86/resctrl: Prepare for new Sub-NUMA Cluster (SNC) monitor files")
Signed-off-by: Qinyun Tan <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Reviewed-by: Reinette Chatre <[email protected]>
Tested-by: Tony Luck <[email protected]>
Link: https://lore.kernel.org/[email protected]
A lockdep fix removed two rdt_last_cmd_clear() calls that were used to
clear the last_cmd_status buffer but called without holding the required
rdtgroup_mutex.
The impacted resctrl commands are writing to the cpus or cpus_list files
and creating a new monitor or control group. With stale data in the
last_cmd_status buffer the impacted resctrl commands report the stale error
on success, or append its own failure message to the stale error on
failure.
Consequently, restore the rdt_last_cmd_clear() calls after acquiring
rdtgroup_mutex.
Fixes: c8eafe1495 ("x86/resctrl: Fix potential lockdep warning")
Signed-off-by: Zeng Heng <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Reinette Chatre <[email protected]>
Link: https://lore.kernel.org/all/[email protected]
Resctrl is a filesystem interface to hardware that provides cache
allocation policy and bandwidth control for groups of tasks or CPUs.
To support more than one architecture, resctrl needs to live in /fs/.
Move the code that is concerned with the filesystem interface to
/fs/resctrl.
Signed-off-by: James Morse <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Reviewed-by: Reinette Chatre <[email protected]>
Reviewed-by: Fenghua Yu <[email protected]>
Tested-by: Fenghua Yu <[email protected]>
Tested-by: Tony Luck <[email protected]>
Link: https://lore.kernel.org/[email protected]
Qinyun Tan