Per-package locks potentially reduce the contention when compared to the
system-wide approach of the previous CQM/CMT driver.
Lockdep needs lock_class_key's to be statically initialized and/or use
nesting, but nesting is currently hard-coded for up to 8 levels and it's
fragile to depend on lockdep internals.
To circumvent this problem, statically define CMT_MAX_NR_PKGS number of
lock_class_key's.
Additional details in code's comments.
Signed-off-by: David Carrillo-Cisneros <davi...@google.com>
---
arch/x86/events/intel/cmt.c | 22 ++++++++++++++++++++++
arch/x86/events/intel/cmt.h | 8 ++++++++
2 files changed, 30 insertions(+)
diff --git a/arch/x86/events/intel/cmt.c b/arch/x86/events/intel/cmt.c
index 267a9ec..f12a06b 100644
--- a/arch/x86/events/intel/cmt.c
+++ b/arch/x86/events/intel/cmt.c
@@ -7,6 +7,14 @@
#include "cmt.h"
#include "../perf_event.h"
+/* Increase as needed as Intel CPUs grow. */
+#define CMT_MAX_NR_PKGS 8
+
+#ifdef CONFIG_LOCKDEP
+static struct lock_class_key mutex_keys[CMT_MAX_NR_PKGS];
+static struct lock_class_key lock_keys[CMT_MAX_NR_PKGS];
+#endif
+
static DEFINE_MUTEX(cmt_mutex);
static unsigned int cmt_l3_scale; /* cmt hw units to bytes. */
@@ -51,6 +59,12 @@ static struct pkg_data *alloc_pkg_data(int cpu)
int numa_node = cpu_to_node(cpu);
u16 pkgid = topology_logical_package_id(cpu);
+ if (pkgid >= CMT_MAX_NR_PKGS) {
+ pr_err("CMT_MAX_NR_PKGS of %d is insufficient for logical
packages.\n",
+ CMT_MAX_NR_PKGS);
+ return ERR_PTR(-ENOSPC);
+ }
+
if (c->x86_cache_occ_scale != cmt_l3_scale) {
/* 0 scale must have been converted to 1 automatically. */
if (c->x86_cache_occ_scale || cmt_l3_scale != 1) {
@@ -65,9 +79,17 @@ static struct pkg_data *alloc_pkg_data(int cpu)
pkgd->max_rmid = c->x86_cache_max_rmid;
+ mutex_init(&pkgd->mutex);
+ raw_spin_lock_init(&pkgd->lock);
+
pkgd->work_cpu = cpu;
pkgd->pkgid = pkgid;
+#ifdef CONFIG_LOCKDEP
+ lockdep_set_class(&pkgd->mutex, &mutex_keys[pkgid]);
+ lockdep_set_class(&pkgd->lock, &lock_keys[pkgid]);
+#endif
+
__min_max_rmid = min(__min_max_rmid, pkgd->max_rmid);
return pkgd;
diff --git a/arch/x86/events/intel/cmt.h b/arch/x86/events/intel/cmt.h
index 8c16797..55416db 100644
--- a/arch/x86/events/intel/cmt.h
+++ b/arch/x86/events/intel/cmt.h
@@ -11,11 +11,16 @@
* Rules:
* - cmt_mutex: Hold for CMT init/terminate, event init/terminate,
* cgroup start/stop.
+ * - Hold pkg->mutex and pkg->lock in _all_ active packages to traverse or
+ * change the monr hierarchy.
+ * - pkgd->lock: Hold in current package to access that pkgd's members.
*/
/**
* struct pkg_data - Per-package CMT data.
*
+ * @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.
* It must be in the package associated to its
* instance of pkg_data.
@@ -23,6 +28,9 @@
* @pkgid: The logical package id for this pkgd.
*/
struct pkg_data {
+ struct mutex mutex;
+ raw_spinlock_t lock;
+
unsigned int work_cpu;
u32 max_rmid;
u16 pkgid;
--
2.8.0.rc3.226.g39d4020
