[PATCH v2 00/32] 2nd Iteration of Cache QoS Monitoring support.

David Carrillo-Cisneros
2016-05-11T23:02:41Z

This series introduces the next iteration of kernel support for the
Cache QoS Monitoring (CQM) technology available in Intel Xeon processors.

One of the main limitations of the previous version is the inability
to simultaneously monitor:
1) cpu event and any other event in that cpu.
2) cgroup events for cgroups in same descendancy line.
3) cgroup events and any thread event of a cgroup in the same
descendancy line.

Another limitation is that monitoring for a cgroup was enabled/disabled by
the existence of a perf event for that cgroup. Since the event
llc_occupancy measures changes in occupancy rather than total occupancy,
in order to read meaningful llc_occupancy values, an event should be
enabled for a long enough period of time. The overhead in context switches
caused by the perf events is undesired in some sensitive scenarios.

This series of patches addresses the shortcomings mentioned above and,
add some other improvements. The main changes are:
- No more potential conflicts between different events. New
version builds a hierarchy of RMIDs that captures the dependency
between monitored cgroups. llc_occupancy for cgroup is the sum of
llc_occupancies for that cgroup RMID and all other RMIDs in the
cgroups subtree (both monitored cgroups and threads).

- A cgroup integration that allows to monitor the a cgroup without
creating a perf event, decreasing the context switch overhead.
Monitoring is controlled by a boolean cgroup subsystem attribute
in each perf cgroup, this is:

echo 1 > cgroup_path/perf_event.cqm_cont_monitoring

starts CQM monitoring whether or not there is a perf_event
attached to the cgroup. Setting the attribute to 0 makes
monitoring dependent on the existence of a perf_event.
A perf_event is always required in order to read llc_occupancy.
This cgroup integration uses Intel's PQR code and is intended to
be used by upcoming versions of Intel's CAT.

- A more stable rotation algorithm: New algorithm uses SLOs that
guarantee:
- A minimum of enabled time for monitored cgroups and
threads.
- A maximum time disabled before error is introduced by
reusing dirty RMIDs.
- A minimum rate at which RMIDs recycling must progress.

- Reduced impact of stealing/rotation of RMIDs: The new algorithm
accounts the residual occupancy held by limbo RMIDs towards the
former owner of the limbo RMID, decreasing the error introduced
by RMID rotation.
It also allows a limbo RMID to be reused by its former owner when
appropriate, decreasing the potential error of reusing dirty RMIDs
and allowing to make progress even if most limbo RMIDs do not
drop occupancy fast enough.

- Elimination of pmu::count: perf generic's perf_event_count()
perform a quick add of atomic types. The introduction of
pmu::count in the previous CQM series to read occupancy for thread
events changed the behavior of perf_event_count() by performing a
potentially slow IPI and write/read to MSR. It also made pmu::read
to have different behaviors depending on whether the event was a
cpu/cgroup event or a thread. This patches serie removes the custom
pmu::count from CQM and provides a consistent behavior for all
calls of perf_event_read .

- Added error return for pmu::read: Reads to CQM events may fail
due to stealing of RMIDs, even after successfully adding an event
to a PMU. This patch series expands pmu::read with an int return
value and propagates the error to callers that can fail
(ie. perf_read).
The ability to fail of pmu::read is consistent with the recent
changes that allow perf_event_read to fail for transactional
reading of event groups.

- Introduces the field pmu_event_flags that contain flags set by
the PMU to signal variations on the default behavior to perf's
generic code. In this series, three flags are introduced:
- PERF_CGROUP_NO_RECURSION : Signals generic code to add
events of the cgroup ancestors of a cgroup.
- PERF_INACTIVE_CPU_READ_PKG: Signals generic coda that
this CPU event can be read in any CPU in its event::cpu's
package, even if the event is not active.
- PERF_INACTIVE_EV_READ_ANY_CPU: Signals generic code that
this event can be read in any CPU in any package in the
system even if the event is not active.
Using the above flags takes advantage of the CQM's hw ability to
read llc_occupancy even when the associated perf event is not
running in a CPU.

This patch series also updates the perf tool to fix error handling and to
better handle the idiosyncrasies of snapshot and per-pkg events.

Changes in 2nd version:
- As requested by Peter Z., redo commit history to completely remove
old version of CQM in a single patch.
- Use topology_max_packages and fix build errors reported by
Vikas Shivappa.
- Split largest patches, clean up.
- Rebased to peterz/queue perf/core .

David Carrillo-Cisneros (31):
perf/x86/intel/cqm: remove previous version of CQM and MBM
perf/x86/intel/cqm: software cache for MSR_IA32_PQR_ASSOC
x86/intel,cqm: add CONFIG_INTEL_RDT configuration flag
perf/x86/intel/cqm: add constants for CQM
perf/x86/intel/cqm: encapsulate per-package RMIDs
perf/x86/intel/cqm: add per-package RMIDs, data and locks
perf/x86/intel/cqm: add helpers for per-package locking
perf/x86/intel/cqm: add pmu sysfs attribute
perf/x86/intel/cqm: basic RMID hierarchy with per package RMIDs
perf/x86/intel/cqm: introduce (I)state and limbo prmids
perf/x86/intel/cqm: add per-package RMID rotation
perf/x86/intel/cqm: schedule work for rotation task
perf/x86/intel/cqm: add polled update of RMID's llc_occupancy
perf/x86/intel/cqm: add preallocation of anodes
perf/core: add hooks to expose architecture specific features in
perf_cgroup
perf/x86/intel/cqm: add cgroup support
perf/core,perf/x86/intel/cqm: add pmu::event_terminate
perf/core: introduce PMU event flag PERF_CGROUP_NO_RECURSION
x86/intel/cqm: use PERF_CGROUP_NO_RECURSION in CQM
perf/x86/intel/cqm: handle inherit event and inherit_stat flag
perf/x86/intel/cqm: introduce read_subtree
perf/core: introduce PERF_INACTIVE_*_READ_* flags
perf/x86/intel/cqm: use PERF_INACTIVE_*_READ_* flags in CQM
sched: introduce the finish_arch_pre_lock_switch() scheduler hook
perf/x86/intel/cqm: integrate CQM cgroups with scheduler
perf/x86/intel/cqm: make one write of PQR_ASSOC per ctx switch
perf/core: add perf_event cgroup hooks for subsystem attributes
perf/x86/intel/cqm: add CQM attributes to perf_event cgroup
perf,perf/x86,perf/powerpc,perf/arm,perf/*: add int error return to
pmu::read
perf,perf/x86: add hook perf_event_arch_exec
perf/stat: revamp read error handling, snapshot and per_pkg events

Stephane Eranian (1):
perf/stat: fix bug in handling events in error state

arch/alpha/kernel/perf_event.c | 3 +-
arch/arc/kernel/perf_event.c | 3 +-
arch/arm64/include/asm/hw_breakpoint.h | 2 +-
arch/arm64/kernel/hw_breakpoint.c | 3 +-
arch/metag/kernel/perf/perf_event.c | 5 +-
arch/mips/kernel/perf_event_mipsxx.c | 3 +-
arch/powerpc/include/asm/hw_breakpoint.h | 2 +-
arch/powerpc/kernel/hw_breakpoint.c | 3 +-
arch/powerpc/perf/core-book3s.c | 11 +-
arch/powerpc/perf/core-fsl-emb.c | 5 +-
arch/powerpc/perf/hv-24x7.c | 5 +-
arch/powerpc/perf/hv-gpci.c | 3 +-
arch/s390/kernel/perf_cpum_cf.c | 5 +-
arch/s390/kernel/perf_cpum_sf.c | 3 +-
arch/sh/include/asm/hw_breakpoint.h | 2 +-
arch/sh/kernel/hw_breakpoint.c | 3 +-
arch/sparc/kernel/perf_event.c | 2 +-
arch/tile/kernel/perf_event.c | 3 +-
arch/x86/Kconfig | 7 +
arch/x86/events/amd/ibs.c | 2 +-
arch/x86/events/amd/iommu.c | 5 +-
arch/x86/events/amd/uncore.c | 3 +-
arch/x86/events/core.c | 3 +-
arch/x86/events/intel/Makefile | 3 +-
arch/x86/events/intel/bts.c | 3 +-
arch/x86/events/intel/cqm.c | 3842 +++++++++++++++++++++---------
arch/x86/events/intel/cqm.h | 532 +++++
arch/x86/events/intel/cstate.c | 3 +-
arch/x86/events/intel/pt.c | 3 +-
arch/x86/events/intel/rapl.c | 3 +-
arch/x86/events/intel/uncore.c | 3 +-
arch/x86/events/intel/uncore.h | 2 +-
arch/x86/events/msr.c | 3 +-
arch/x86/include/asm/hw_breakpoint.h | 2 +-
arch/x86/include/asm/perf_event.h | 44 +
arch/x86/include/asm/pqr_common.h | 84 +
arch/x86/include/asm/processor.h | 4 +
arch/x86/kernel/cpu/Makefile | 4 +
arch/x86/kernel/cpu/pqr_common.c | 33 +
arch/x86/kernel/hw_breakpoint.c | 3 +-
arch/x86/kvm/pmu.h | 10 +-
drivers/bus/arm-cci.c | 3 +-
drivers/bus/arm-ccn.c | 3 +-
drivers/perf/arm_pmu.c | 3 +-
include/linux/perf_event.h | 92 +-
kernel/events/core.c | 160 +-
kernel/sched/core.c | 1 +
kernel/sched/sched.h | 3 +
kernel/trace/bpf_trace.c | 5 +-
tools/perf/builtin-stat.c | 43 +-
tools/perf/util/counts.h | 19 +
tools/perf/util/evsel.c | 44 +-
tools/perf/util/evsel.h | 8 +-
tools/perf/util/stat.c | 35 +-
54 files changed, 3760 insertions(+), 1326 deletions(-)
create mode 100644 arch/x86/events/intel/cqm.h
create mode 100644 arch/x86/include/asm/pqr_common.h
create mode 100644 arch/x86/kernel/cpu/pqr_common.c

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2.8.0.rc3.226.g39d4020