A Resource Monitoring ID (RMID) is a hardware ID used to track cache
occupancy and memory bandwidth. The rmids are a per-package resource
and only one can be programmed at a time per logical CPU.
This patch series creates per-package rmids pools and (default)
lazy allocation of rmids (only reserve when a thread runs in a package)
to potentially allow more simultaneous rmid users than the system-wide
approach of the previous CQM/CMT driver.
Signed-off-by: David Carrillo-Cisneros <davi...@google.com>
---
arch/x86/events/intel/cmt.c | 5 +++++
arch/x86/events/intel/cmt.h | 24 +++++++++++++++++++++++-
2 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/arch/x86/events/intel/cmt.c b/arch/x86/events/intel/cmt.c
index 07560e5..5799816 100644
--- a/arch/x86/events/intel/cmt.c
+++ b/arch/x86/events/intel/cmt.c
@@ -725,6 +725,11 @@ static struct pkg_data *alloc_pkg_data(int cpu)
return ERR_PTR(-ENOMEM);
pkgd->max_rmid = c->x86_cache_max_rmid;
+ if (pkgd->max_rmid >= CMT_MAX_NR_RMIDS) {
+ pr_err("CPU Package %d supports %d RMIDs. Using %d only.\n",
+ pkgid, pkgd->max_rmid, CMT_MAX_NR_RMIDS - 1);
+ pkgd->max_rmid = CMT_MAX_NR_RMIDS - 1;
+ }
mutex_init(&pkgd->mutex);
raw_spin_lock_init(&pkgd->lock);
diff --git a/arch/x86/events/intel/cmt.h b/arch/x86/events/intel/cmt.h
index 66b078a..6211392 100644
--- a/arch/x86/events/intel/cmt.h
+++ b/arch/x86/events/intel/cmt.h
@@ -3,6 +3,11 @@
* (formerly Intel Cache QoS Monitoring, CQM)
*
*
+ * A Resource Monitoring ID (RMID) is a hardware ID used in Intel RDT to
+ * monitor cache and memory events such as LLC Occupancy and Memory
+ * Bandwidth. Changes in such metrics that are caused by a CPU are
+ * counted towards the rmid active in that CPU at the time.
+ *
* A "Monitored Resource" (monr) is the entity monitored by CMT and MBM.
* In order to monitor a cgroups and/or thread, it must be associated to
* a monr. A monr is active in a CPU when a thread that is associated to
@@ -28,7 +33,8 @@
* cgroup or process.
*
* Each monr has a package monr (pmonr) for each package with at least one
- * online cpu. The pmonr handles the CMT and MBM monitoring within its package.
+ * online cpu. The pmonr handles the CMT and MBM monitoring within its package
+ * by managing the rmid to write into each CPU that runs a monitored thread.
*
*
* Locking
@@ -55,9 +61,22 @@ struct pmonr {
struct pkg_data *pkgd;
};
+/*
+ * Compile constant required for bitmap macros.
+ * Broadwell EP has 2 rmids per logical core, use twice as many as upper bound.
+ * 128 is a reasonable upper bound for logical cores per package for the
+ * foreseeable future. Adjust as CPUs grow.
+ */
+#define CMT_MAX_NR_RMIDS (2 * 2 * 128)
+#define CMT_MAX_NR_RMIDS_BYTES DIV_ROUND_UP(CMT_MAX_NR_RMIDS, BITS_PER_BYTE)
+#define CMT_MAX_NR_RMIDS_LONGS BITS_TO_LONGS(CMT_MAX_NR_RMIDS)
+
/**
* struct pkg_data - Per-package CMT data.
*
+ * @free_rmids: Pool of free rmids.
+ * @dirty_rmids: Pool of "dirty" rmids that are not referenced
+ * by a pmonr.
* @mutex: Hold when modifying this pkg_data.
* @lock: Hold to protect pmonrs in this pkg_data.
* @work_cpu: CPU to run rotation and other batch jobs.
@@ -67,6 +86,9 @@ struct pmonr {
* @pkgid: The logical package id for this pkgd.
*/
struct pkg_data {
+ unsigned long free_rmids[CMT_MAX_NR_RMIDS_LONGS];
+ unsigned long dirty_rmids[CMT_MAX_NR_RMIDS_LONGS];
+
struct mutex mutex;
raw_spinlock_t lock;
--
2.8.0.rc3.226.g39d4020
