[ Upstream commit c2427e70c1630d98966375fffc2b713ab9768a94 ]
The mba_MBps feedback loop increases throttling when a group is using
more bandwidth than the target set by the user in the schemata file, and
decreases throttling when below target.
To avoid possibly stepping throttling up and down on every poll a flag
"delta_comp" is set whenever throttling is changed to indicate that the
actual change in bandwidth should be recorded on the next poll in
"delta_bw". Throttling is only reduced if the current bandwidth plus
delta_bw is below the user target.
This algorithm works well if the workload has steady bandwidth needs.
But it can go badly wrong if the workload moves to a different phase
just as the throttling level changed. E.g. if the workload becomes
essentially idle right as throttling level is increased, the value
calculated for delta_bw will be more or less the old bandwidth level.
If the workload then resumes, Linux may never reduce throttling because
current bandwidth plus delta_bw is above the target set by the user.
Implement a simpler heuristic by assuming that in the worst case the
currently measured bandwidth is being controlled by the current level of
throttling. Compute how much it may increase if throttling is relaxed to
the next higher level. If that is still below the user target, then it
is ok to reduce the amount of throttling.
Fixes: ba0f26d8529c ("x86/intel_rdt/mba_sc: Prepare for feedback loop")
Reported-by: Xiaochen Shen <xiaochen.shen@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Tested-by: Xiaochen Shen <xiaochen.shen@intel.com>
Link: https://lore.kernel.org/r/20240122180807.70518-1-tony.luck@intel.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 54e35eb8611cce5550d3d7689679b1a91c864f28 ]
If the BMEC (Bandwidth Monitoring Event Configuration) feature is
supported, the bandwidth events can be configured. The maximum supported
bandwidth bitmask can be read from CPUID:
CPUID_Fn80000020_ECX_x03 [Platform QoS Monitoring Bandwidth Event Configuration]
Bits Description
31:7 Reserved
6:0 Identifies the bandwidth sources that can be tracked.
While at it, move the mask checking to mon_config_write() before
iterating over all the domains. Also, print the valid bitmask when the
user tries to configure invalid event configuration value.
The CPUID details are documented in the Processor Programming Reference
(PPR) Vol 1.1 for AMD Family 19h Model 11h B1 - 55901 Rev 0.25 in the
Link tag.
Fixes: dc2a3e857981 ("x86/resctrl: Add interface to read mbm_total_bytes_config")
Signed-off-by: Babu Moger <babu.moger@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
Link: https://lore.kernel.org/r/669896fa512c7451319fa5ca2fdb6f7e015b5635.1705359148.git.babu.moger@amd.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
The kernel test robot reported kernel-doc warnings here:
monitor.c:34: warning: Cannot understand * @rmid_free_lru A least recently used list of free RMIDs on line 34 - I thought it was a doc line
monitor.c:41: warning: Cannot understand * @rmid_limbo_count count of currently unused but (potentially) on line 41 - I thought it was a doc line
monitor.c:50: warning: Cannot understand * @rmid_entry - The entry in the limbo and free lists. on line 50 - I thought it was a doc line
We don't have a syntax for documenting individual data items via
kernel-doc, so remove the "/**" kernel-doc markers and add a hyphen
for consistency.
Fixes: 6a445edce657 ("x86/intel_rdt/cqm: Add RDT monitoring initialization")
Fixes: 24247aeeabe9 ("x86/intel_rdt/cqm: Improve limbo list processing")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231006235132.16227-1-rdunlap@infradead.org
Pull x86 resctrl update from Dave Hansen: "Reduce redundant counter reads with resctrl refactoring" * tag 'x86_cache_for_6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/resctrl: Avoid redundant counter read in __mon_event_count()
Move the x86 documentation under Documentation/arch/ as a way of cleaning up the top-level directory and making the structure of our docs more closely match the structure of the source directories it describes. All in-kernel references to the old paths have been updated. Acked-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: linux-arch@vger.kernel.org Cc: x86@kernel.org Cc: Borislav Petkov <bp@alien8.de> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/lkml/20230315211523.108836-1-corbet@lwn.net/ Signed-off-by: Jonathan Corbet <corbet@lwn.net>
__mon_event_count() does the per-RMID, per-domain work for user-initiated event count reads and the initialization of new monitor groups. In the initialization case, after resctrl_arch_reset_rmid() calls __rmid_read() to record an initial count for a new monitor group, it immediately calls resctrl_arch_rmid_read(). This re-read of the hardware counter is unnecessary and the following computations are ignored by the caller during initialization. Following return from resctrl_arch_reset_rmid(), just clear the mbm_state and return. This involves moving the mbm_state lookup into the rr->first case, as it's not needed for regular event count reads: the QOS_L3_OCCUP_EVENT_ID case was redundant with the accumulating logic at the end of the function. Signed-off-by: Peter Newman <peternewman@google.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com> Tested-by: Babu Moger <babu.moger@amd.com> Link: https://lore.kernel.org/all/20221220164132.443083-2-peternewman%40google.com
The event configuration for mbm_total_bytes can be changed by the user by writing to the file /sys/fs/resctrl/info/L3_MON/mbm_total_bytes_config. The event configuration settings are domain specific and affect all the CPUs in the domain. Following are the types of events supported: ==== =========================================================== Bits Description ==== =========================================================== 6 Dirty Victims from the QOS domain to all types of memory 5 Reads to slow memory in the non-local NUMA domain 4 Reads to slow memory in the local NUMA domain 3 Non-temporal writes to non-local NUMA domain 2 Non-temporal writes to local NUMA domain 1 Reads to memory in the non-local NUMA domain 0 Reads to memory in the local NUMA domain ==== =========================================================== For example: To change the mbm_total_bytes to count only reads on domain 0, the bits 0, 1, 4 and 5 needs to be set, which is 110011b (in hex 0x33). Run the command: $echo 0=0x33 > /sys/fs/resctrl/info/L3_MON/mbm_total_bytes_config To change the mbm_total_bytes to count all the slow memory reads on domain 1, the bits 4 and 5 needs to be set which is 110000b (in hex 0x30). Run the command: $echo 1=0x30 > /sys/fs/resctrl/info/L3_MON/mbm_total_bytes_config Signed-off-by: Babu Moger <babu.moger@amd.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com> Link: https://lore.kernel.org/r/20230113152039.770054-12-babu.moger@amd.com
The event configuration can be viewed by the user by reading the configuration file /sys/fs/resctrl/info/L3_MON/mbm_local_bytes_config. The event configuration settings are domain specific and will affect all the CPUs in the domain. Following are the types of events supported: ==== =========================================================== Bits Description ==== =========================================================== 6 Dirty Victims from the QOS domain to all types of memory 5 Reads to slow memory in the non-local NUMA domain 4 Reads to slow memory in the local NUMA domain 3 Non-temporal writes to non-local NUMA domain 2 Non-temporal writes to local NUMA domain 1 Reads to memory in the non-local NUMA domain 0 Reads to memory in the local NUMA domain ==== =========================================================== By default, the mbm_local_bytes_config is set to 0x15 to count all the local event types. For example: $cat /sys/fs/resctrl/info/L3_MON/mbm_local_bytes_config 0=0x15;1=0x15;2=0x15;3=0x15 In this case, the event mbm_local_bytes is configured with 0x15 on domains 0 to 3. Signed-off-by: Babu Moger <babu.moger@amd.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com> Link: https://lore.kernel.org/r/20230113152039.770054-11-babu.moger@amd.com
The event configuration can be viewed by the user by reading the configuration file /sys/fs/resctrl/info/L3_MON/mbm_total_bytes_config. The event configuration settings are domain specific and will affect all the CPUs in the domain. Following are the types of events supported: ==== =========================================================== Bits Description ==== =========================================================== 6 Dirty Victims from the QOS domain to all types of memory 5 Reads to slow memory in the non-local NUMA domain 4 Reads to slow memory in the local NUMA domain 3 Non-temporal writes to non-local NUMA domain 2 Non-temporal writes to local NUMA domain 1 Reads to memory in the non-local NUMA domain 0 Reads to memory in the local NUMA domain ==== =========================================================== By default, the mbm_total_bytes_config is set to 0x7f to count all the event types. For example: $cat /sys/fs/resctrl/info/L3_MON/mbm_total_bytes_config 0=0x7f;1=0x7f;2=0x7f;3=0x7f In this case, the event mbm_total_bytes is configured with 0x7f on domains 0 to 3. Signed-off-by: Babu Moger <babu.moger@amd.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com> Link: https://lore.kernel.org/r/20230113152039.770054-10-babu.moger@amd.com
Add a new field in struct mon_evt to support Bandwidth Monitoring Event Configuration (BMEC) and also update the "mon_features" display. The resctrl file "mon_features" will display the supported events and files that can be used to configure those events if monitor configuration is supported. Before the change: $ cat /sys/fs/resctrl/info/L3_MON/mon_features llc_occupancy mbm_total_bytes mbm_local_bytes After the change when BMEC is supported: $ cat /sys/fs/resctrl/info/L3_MON/mon_features llc_occupancy mbm_total_bytes mbm_total_bytes_config mbm_local_bytes mbm_local_bytes_config Signed-off-by: Babu Moger <babu.moger@amd.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com> Link: https://lore.kernel.org/r/20230113152039.770054-9-babu.moger@amd.com