/*
* Intel Cache Quality-of-Service Monitoring (CQM) support.
*
* Based very, very heavily on work by Peter Zijlstra.
*/
#include <linux/perf_event.h>
#include <linux/slab.h>
#include <asm/cpu_device_id.h>
#include "perf_event.h"
#define MSR_IA32_PQR_ASSOC 0x0c8f
#define MSR_IA32_QM_CTR 0x0c8e
#define MSR_IA32_QM_EVTSEL 0x0c8d
static unsigned int cqm_max_rmid = -1;
static unsigned int cqm_l3_scale; /* supposedly cacheline size */
struct intel_cqm_state {
raw_spinlock_t lock;
int rmid;
int cnt;
};
static DEFINE_PER_CPU(struct intel_cqm_state, cqm_state);
/*
* Protects cache_cgroups and cqm_rmid_free_lru and cqm_rmid_limbo_lru.
* Also protects event->hw.cqm_rmid
*
* Hold either for stability, both for modification of ->hw.cqm_rmid.
*/
static DEFINE_MUTEX(cache_mutex);
static DEFINE_RAW_SPINLOCK(cache_lock);
/*
* Groups of events that have the same target(s), one RMID per group.
*/
static LIST_HEAD(cache_groups);
/*
* Mask of CPUs for reading CQM values. We only need one per-socket.
*/
static cpumask_t cqm_cpumask;
#define RMID_VAL_ERROR (1ULL << 63)
#define RMID_VAL_UNAVAIL (1ULL << 62)
#define QOS_L3_OCCUP_EVENT_ID (1 << 0)
#define QOS_EVENT_MASK QOS_L3_OCCUP_EVENT_ID
/*
* This is central to the rotation algorithm in __intel_cqm_rmid_rotate().
*
* This rmid is always free and is guaranteed to have an associated
* near-zero occupancy value, i.e. no cachelines are tagged with this
* RMID, once __intel_cqm_rmid_rotate() returns.
*/
static unsigned int intel_cqm_rotation_rmid;
#define INVALID_RMID (-1)
/*
* Is @rmid valid for programming the hardware?
*
* rmid 0 is reserved by the hardware for all non-monitored tasks, which
* means that we should never come across an rmid with that value.
* Likewise, an rmid value of -1 is used to indicate "no rmid currently
* assigned" and is used as part of the rotation code.
*/
static inline bool __rmid_valid(unsigned int rmid)
{
if (!rmid || rmid == INVALID_RMID)
return false;
return true;
}
static u64 __rmid_read(unsigned int rmid)
{
u64 val;
/*
* Ignore the SDM, this thing is _NOTHING_ like a regular perfcnt,
* it just says that to increase confusion.
*/
wrmsr(MSR_IA32_QM_EVTSEL, QOS_L3_OCCUP_EVENT_ID, rmid);
rdmsrl(MSR_IA32_QM_CTR, val);
/*
* Aside from the ERROR and UNAVAIL bits, assume this thing returns
* the number of cachelines tagged with @rmid.
*/
return val;
}
enum rmid_recycle_state {
RMID_YOUNG = 0,
RMID_AVAILABLE,
RMID_DIRTY,
};
struct cqm_rmid_entry {
unsigned int rmid;
enum rmid_recycle_state state;
struct list_head list;
unsigned long queue_time;
};
/*
* cqm_rmid_free_lru - A least recently used list of RMIDs.
*
* Oldest entry at the head, newest (most recently used) entry at the
* tail. This list is never traversed, it's only used to keep track of
* the lru order. That is, we only pick entries of the head or insert
* them on the tail.
*
* All entries on the list are 'free', and their RMIDs are not currently
* in use. To mark an RMID as in use, remove its entry from the lru
* list.
*
*
* cqm_rmid_limbo_lru - list of currently unused but (potentially) dirty RMIDs.
*
* This list is contains RMIDs that no one is currently using but that
* may have a non-zero occupancy value associated with them. The
* rotation worker moves RMIDs from the limbo list to the free list once
* the occupancy value drops below __intel_cqm_threshold.
*
* Both lists are protected by cache_mutex.
*/
static LIST_HEAD(cqm_rmid_free_lru);
static LIST_HEAD(cqm_rmid_limbo_lru);
/*
* We use a simple array of pointers so that we can lookup a struct
* cqm_rmid_entry in O(1). This alleviates the callers of __get_rmid()
* and __put_rmid() from having to worry about dealing with struct
* cqm_rmid_entry - they just deal with rmids, i.e. integers.
*
* Once this array is initialized it is read-only. No locks are required
* to access it.
*
* All entries for all RMIDs can be looked up in the this array at all
* times.
*/
static struct cqm_rmid_entry **cqm_rmid_ptrs;
static inline struct cqm_rmid_entry *__rmid_entry(int rmid)
{
struct cqm_rmid_entry *entry;
entry = cqm_rmid_ptrs[rmid];
WARN_ON(entry->rmid != rmid);
return entry;
}
/*
* Returns < 0 on fail.
*
* We expect to be called with cache_mutex held.
*/
static int __get_rmid(void)
{
struct cqm_rmid_entry *entry;
lockdep_assert_held(&cache_mutex);
if (list_empty(&cqm_rmid_free_lru))
return INVALID_RMID;
entry = list_first_entry(&cqm_rmid_free_lru, struct cqm_rmid_entry, list);
list_del(&entry->list);
return entry->rmid;
}
static void __put_rmid(unsigned int rmid)
{
struct cqm_rmid_entry *entry;
lockdep_assert_held(&cache_mutex);
WARN_ON(!__rmid_valid(rmid));
entry = __rmid_entry(rmid);
entry->queue_time = jiffies;
entry->state = RMID_YOUNG;
list_add_tail(&entry->list, &cqm_rmid_limbo_lru);
}
static int intel_cqm_setup_rmid_cache(void)
{
struct cqm_rmid_entry *entry;
unsigned int nr_rmids;
int r = 0;
nr_rmids = cqm_max_rmid + 1;
cqm_rmid_ptrs = kmalloc(sizeof(struct cqm_rmid_entry *) *
nr_rmids, GFP_KERNEL);
if (!cqm_rmid_ptrs)
return -ENOMEM;
for (; r <= cqm_max_rmid; r++) {
struct cqm_rmid_entry *entry;
entry = kmalloc(sizeof(*entry), GFP_KERNEL);
if (!entry)
goto fail;
INIT_LIST_HEAD(&entry->list);
entry->rmid = r;
cqm_rmid_ptrs[r] = entry;
list_add_tail(&entry->list, &cqm_rmid_free_lru);
}
/*
* RMID 0 is special and is always allocated. It's used for all
* tasks that are not monitored.
*/
entry = __rmid_entry(0);
list_del(&entry->list);
mutex_lock(&cache_mutex);
intel_cqm_rotation_rmid = __get_rmid();
mutex_unlock(&cache_mutex);
return 0;
fail:
while (r--)
kfree(cqm_rmid_ptrs[r]);
kfree(cqm_rmid_ptrs);
return -ENOMEM;
}
/*
* Determine if @a and @b measure the same set of tasks.
*
* If @a and @b measure the same set of tasks then we want to share a
* single RMID.
*/
static bool __match_event(struct perf_event *a, struct perf_event *b)
{
/* Per-cpu and task events don't mix */
if ((a->attach_state & PERF_ATTACH_TASK) !=
(b->attach_state & PERF_ATTACH_TASK))
return false;
#ifdef CONFIG_CGROUP_PERF
if (a->cgrp != b->cgrp)
return false;
#endif
/* If not task event, we're machine wide */
if (!(b->attach_state & PERF_ATTACH_TASK))
return true;
/*
* Events that target same task are placed into the same cache group.
*/
if (a->hw.target == b->hw.target)
return true;
/*
* Are we an inherited event?
*/
if (b->parent == a)
return true;
return false;
}
#ifdef CONFIG_CGROUP_PERF
static inline struct perf_cgroup *event_to_cgroup(struct perf_event *event)
{
if (event->attach_state & PERF_ATTACH_TASK)
return perf_cgroup_from_task(event->hw.target);
return event->cgrp;
}
#endif
/*
* Determine if @a's tasks intersect with @b's tasks
*
* There are combinations of events that we explicitly prohibit,
*
* PROHIBITS
* system-wide -> cgroup and task
* cgroup -> system-wide
* -> task in cgroup
* task -> system-wide
* -> task in cgroup
*
* Call this function before allocating an RMID.
*/
static bool __conflict_event(struct perf_event *a, struct perf_event *b)
{
#ifdef CONFIG_CGROUP_PERF
/*
* We can have any number of cgroups but only one system-wide
* event at a time.
*/
if (a->cgrp && b->cgrp) {
struct perf_cgroup *ac = a->cgrp;
struct perf_cgroup *bc = b->cgrp;
/*
* This condition should have been caught in
* __match_event() and we should be sharing an RMID.
*/
WARN_ON_ONCE(ac == bc);
if (cgroup_is_descendant(ac->css.cgroup, bc->css.cgroup) ||
cgroup_is_descendant(bc->css.cgroup, ac->css.cgroup))
return true;
return false;
}
if (a->cgrp || b->cgrp) {
struct perf_cgroup *ac, *bc;
/*
* cgroup and system-wide events are mutually exclusive
*/
if ((a->cgrp && !(b->attach_state & PERF_ATTACH_TASK)) ||
(b->cgrp && !(a->attach_state & PERF_ATTACH_TASK)))
return true;
/*
* Ensure neither event is part of the other's cgroup
*/
ac = event_to_cgroup(a);
bc = event_to_cgroup(b);
if (ac == bc)
return true;
/*
* Must have cgroup and non-intersecting task events.
*/
if (!ac || !bc)
return false;
/*
* We have cgroup and task events, and the task belongs
* to a cgroup. Check for for overlap.
*/
if (cgroup_is_descendant(ac->css.cgroup, bc->css.cgroup) ||
cgroup_is_descendant(bc->css.cgroup, ac->css.cgroup))
return true;
return false;
}
#endif
/*
* If one of them is not a task, same story as above with cgroups.
*/
if (!(a->attach_state & PERF_ATTACH_TASK) ||
!(b->attach_state & PERF_ATTACH_TASK))
return true;
/*
* Must be non-overlapping.
*/
return false;
}
struct rmid_read {
unsigned int rmid;
atomic64_t value;
};
static void __intel_cqm_event_count(void *info);
/*
* Exchange the RMID of a group of events.
*/
static unsigned int
intel_cqm_xchg_rmid(struct perf_event *group, unsigned int rmid)
{
struct perf_event *event;
unsigned int old_rmid = group->hw.cqm_rmid;
struct list_head *head = &group->hw.cqm_group_entry;
lockdep_assert_held(&cache_mutex);
/*
* If our RMID is being deallocated, perform a read now.
*/
if (__rmid_valid(old_rmid) && !__rmid_valid(rmid)) {
struct rmid_read rr = {
.value = ATOMIC64_INIT(0),
.rmid = old_rmid,
};
on_each_cpu_mask(&cqm_cpumask, __intel_cqm_event_count,
&rr, 1);
local64_set(&group->count, atomic64_read(&rr.value));
}
raw_spin_lock_irq(&cache_lock);
group->hw.cqm_rmid = rmid;
list_for_each_entry(event, head, hw.cqm_group_entry)
event->hw.cqm_rmid = rmid;
raw_spin_unlock_irq(&cache_lock);
return old_rmid;
}
/*
* If we fail to assign a new RMID for intel_cqm_rotation_rmid because
* cachelines are still tagged with RMIDs in limbo, we progressively
* increment the threshold until we find an RMID in limbo with <=
* __intel_cqm_threshold lines tagged. This is designed to mitigate the
* problem where cachelines tagged with an RMID are not steadily being
* evicted.
*
* On successful rotations we decrease the threshold back towards zero.
*
* __intel_cqm_max_threshold provides an upper bound on the threshold,
* and is measured in bytes because it's exposed to userland.
*/
static unsigned int __intel_cqm_threshold;
static unsigned int __intel_cqm_max_threshold;
/*
* Test whether an RMID has a zero occupancy value on this cpu.
*/
static void intel_cqm_stable(void *arg)
{
struct cqm_rmid_entry *entry;
list_for_each_entry(entry, &cqm_rmid_limbo_lru, list) {
if (entry->state != RMID_AVAILABLE)
break;
if (__rmid_read(entry->rmid) > __intel_cqm_threshold)
entry->state = RMID_DIRTY;
}
}
/*
* If we have group events waiting for an RMID that don't conflict with
* events already running, assign @rmid.
*/
static bool intel_cqm_sched_in_event(unsigned int rmid)
{
struct perf_event *leader, *event;
lockdep_assert_held(&cache_mutex);
leader = list_first_entry(&cache_groups, struct perf_event,
hw.cqm_groups_entry);
event = leader;
list_for_each_entry_continue(event, &cache_groups,
hw.cqm_groups_entry) {
if (__rmid_valid(event->hw.cqm_rmid))
continue;
if (__conflict_event(event, leader))
continue;
intel_cqm_xchg_rmid(event, rmid);
return true;
}
return false;
}
/*
* Initially use this constant for both the limbo queue time and the
* rotation timer interval, pmu::hrtimer_interval_ms.
*
* They don't need to be the same, but the two are related since if you
* rotate faster than you recycle RMIDs, you may run out of available
* RMIDs.
*/
#define RMID_DEFAULT_QUEUE_TIME 250 /* ms */
static unsigned int __rmid_queue_time_ms = RMID_DEFAULT_QUEUE_TIME;
/*
* intel_cqm_rmid_stabilize - move RMIDs from limbo to free list
* @nr_available: number of freeable RMIDs on the limbo list
*
* Quiescent state; wait for all 'freed' RMIDs to become unused, i.e. no
* cachelines are tagged with those RMIDs. After this we can reuse them
* and know that the current set of active RMIDs is stable.
*
* Return %true or %false depending on whether stabilization needs to be
* reattempted.
*
* If we return %true then @nr_available is updated to indicate the
* number of RMIDs on the limbo list that have been queued for the
* minimum queue time (RMID_AVAILABLE), but whose data occupancy values
* are above __intel_cqm_threshold.
*/
static bool intel_cqm_rmid_stabilize(unsigned int *available)
{
struct cqm_rmid_entry *entry, *tmp;
lockdep_assert_held(&cache_mutex);
*available = 0;
list_for_each_entry(entry, &cqm_rmid_limbo_lru, list) {
unsigned long min_queue_time;
unsigned long now = jiffies;
/*
* We hold RMIDs placed into limbo for a minimum queue
* time. Before the minimum queue time has elapsed we do
* not recycle RMIDs.
*
* The reasoning is that until a sufficient time has
* passed since we stopped using an RMID, any RMID
* placed onto the limbo list will likely still have
* data tagged in the cache, which means we'll probably
* fail to recycle it anyway.
*
* We can save ourselves an expensive IPI by skipping
* any RMIDs that have not been queued for the minimum
* time.
*/
min_queue_time = entry->queue_time +
msecs_to_jiffies(__rmid_queue_time_ms);
if (time_after(min_queue_time, now))
break;
entry->state = RMID_AVAILABLE;
(*available)++;
}
/*
* Fast return if none of the RMIDs on the limbo list have been
* sitting on the queue for the minimum queue time.
*/
if (!*available)
return false;
/*
* Test whether an RMID is free for each package.
*/
on_each_cpu_mask(&cqm_cpumask, intel_cqm_stable, NULL, true);
list_for_each_entry_safe(entry, tmp, &cqm_rmid_limbo_lru, list) {
/*
* Exhausted all RMIDs that have waited min queue time.
*/
if (entry->state == RMID_YOUNG)
break;
if (entry->state == RMID_DIRTY)
continue;
list_del(&entry->list); /* remove from limbo */
/*
* The rotation RMID gets priority if it's
* currently invalid. In which case, skip adding
* the RMID to the the free lru.
*/
if (!__rmid_valid(intel_cqm_rotation_rmid)) {
intel_cqm_rotation_rmid = entry->rmid;
continue;
}
/*
* If we have groups waiting for RMIDs, hand
* them one now provided they don't conflict.
*/
if (intel_cqm_sched_in_event(entry->rmid))
continue;
/*
* Otherwise place it onto the free list.
*/
list_add_tail(&entry->list, &cqm_rmid_free_lru);
}
return __rmid_valid(intel_cqm_rotation_rmid);
}
/*
* Pick a victim group and move it to the tail of the group list.
* @next: The first group without an RMID
*/
static void __intel_cqm_pick_and_rotate(struct perf_event *next)
{
struct perf_event *rotor;
unsigned int rmid;
lockdep_assert_held(&cache_mutex);
rotor = list_first_entry(&cache_groups, struct perf_event,
hw.cqm_groups_entry);
/*
* The group at the front of the list should always have a valid
* RMID. If it doesn't then no groups have RMIDs assigned and we
* don't need to rotate the list.
*/
if (next == rotor)
return;
rmid = intel_cqm_xchg_rmid(rotor, INVALID_RMID);
__put_rmid(rmid);
list_rotate_left(&cache_groups);
}
/*
* Deallocate the RMIDs from any events that conflict with @event, and
* place them on the back of the group list.
*/
static void intel_cqm_sched_out_conflicting_events(struct perf_event *event)
{
struct perf_event *group, *g;
unsigned int rmid;
lockdep_assert_held(&cache_mutex);
list_for_each_entry_safe(group, g, &cache_groups, hw.cqm_groups_entry) {
if (group == event)
continue;
rmid = group->hw.cqm_rmid;
/*
* Skip events that don't have a valid RMID.
*/
if (!__rmid_valid(rmid))
continue;
/*
* No conflict? No problem! Leave the event alone.
*/
if (!__conflict_event(group, event))
continue;
intel_cqm_xchg_rmid(group, INVALID_RMID);
__put_rmid(rmid);
}
}
/*
* Attempt to rotate the groups and assign new RMIDs.
*
* We rotate for two reasons,
* 1. To handle the scheduling of conflicting events
* 2. To recycle RMIDs
*
* Rotating RMIDs is complicated because the hardware doesn't give us
* any clues.
*
* There's problems with the hardware interface; when you change the
* task:RMID map cachelines retain their 'old' tags, giving a skewed
* picture. In order to work around this, we must always keep one free
* RMID - intel_cqm_rotation_rmid.
*
* Rotation works by taking away an RMID from a group (the old RMID),
* and assigning the free RMID to another group (the new RMID). We must
* then wait for the old RMID to not be used (no cachelines tagged).
* This ensure that all cachelines are tagged with 'active' RMIDs. At
* this point we can start reading values for the new RMID and treat the
* old RMID as the free RMID for the next rotation.
*
* Return %true or %false depending on whether we did any rotating.
*/
static bool __intel_cqm_rmid_rotate(void)
{
struct perf_event *group, *start = NULL;
unsigned int threshold_limit;
unsigned int nr_needed = 0;
unsigned int nr_available;
bool rotated = false;
mutex_lock(&cache_mutex);
again:
/*
* Fast path through this function if there are no groups and no
* RMIDs that need cleaning.
*/
if (list_empty(&cache_groups) && list_empty(&cqm_rmid_limbo_lru))
goto out;
list_for_each_entry(group, &cache_groups, hw.cqm_groups_entry) {
if (!__rmid_valid(group->hw.cqm_rmid)) {
if (!start)
start = group;
nr_needed++;
}
}
/*
* We have some event groups, but they all have RMIDs assigned
* and no RMIDs need cleaning.
*/
if (!nr_needed && list_empty(&cqm_rmid_limbo_lru))
goto out;
if (!nr_needed)
goto stabilize;
/*
* We have more event groups without RMIDs than available RMIDs,
* or we have event groups that conflict with the ones currently
* scheduled.
*
* We force deallocate the rmid of the group at the head of
* cache_groups. The first event group without an RMID then gets
* assigned intel_cqm_rotation_rmid. This ensures we always make
* forward progress.
*
* Rotate the cache_groups list so the previous head is now the
* tail.
*/
__intel_cqm_pick_and_rotate(start);
/*
* If the rotation is going to succeed, reduce the threshold so
* that we don't needlessly reuse dirty RMIDs.
*/
if (__rmid_valid(intel_cqm_rotation_rmid)) {
intel_cqm_xchg_rmid(start, intel_cqm_rotation_rmid);
intel_cqm_rotation_rmid = __get_rmid();
intel_cqm_sched_out_conflicting_events(start);
if (__intel_cqm_threshold)
__intel_cqm_threshold--;
}
rotated = true;
stabilize:
/*
* We now need to stablize the RMID we freed above (if any) to
* ensure that the next time we rotate we have an RMID with zero
* occupancy value.
*
* Alternatively, if we didn't need to perform any rotation,
* we'll have a bunch of RMIDs in limbo that need stabilizing.
*/
threshold_limit = __intel_cqm_max_threshold / cqm_l3_scale;
while (intel_cqm_rmid_stabilize(&nr_available) &&
__intel_cqm_threshold < threshold_limit) {
unsigned int steal_limit;
/*
* Don't spin if nobody is actively waiting for an RMID,
* the rotation worker will be kicked as soon as an
* event needs an RMID anyway.
*/
if (!nr_needed)
break;
/* Allow max 25% of RMIDs to be in limbo. */
steal_limit = (cqm_max_rmid + 1) / 4;
/*
* We failed to stabilize any RMIDs so our rotation
* logic is now stuck. In order to make forward progress
* we have a few options:
*
* 1. rotate ("steal") another RMID
* 2. increase the threshold
* 3. do nothing
*
* We do both of 1. and 2. until we hit the steal limit.
*
* The steal limit prevents all RMIDs ending up on the
* limbo list. This can happen if every RMID has a
* non-zero occupancy above threshold_limit, and the
* occupancy values aren't dropping fast enough.
*
* Note that there is prioritisation at work here - we'd
* rather increase the number of RMIDs on the limbo list
* than increase the threshold, because increasing the
* threshold skews the event data (because we reuse
* dirty RMIDs) - threshold bumps are a last resort.
*/
if (nr_available < steal_limit)
goto again;
__intel_cqm_threshold++;
}
out:
mutex_unlock(&cache_mutex);
return rotated;
}
static void intel_cqm_rmid_rotate(struct work_struct *work);
static DECLARE_DELAYED_WORK(intel_cqm_rmid_work, intel_cqm_rmid_rotate);
static struct pmu intel_cqm_pmu;
static void intel_cqm_rmid_rotate(struct work_struct *work)
{
unsigned long delay;
__intel_cqm_rmid_rotate();
delay = msecs_to_jiffies(intel_cqm_pmu.hrtimer_interval_ms);
schedule_delayed_work(&intel_cqm_rmid_work, delay);
}
/*
* Find a group and setup RMID.
*
* If we're part of a group, we use the group's RMID.
*/
static void intel_cqm_setup_event(struct perf_event *event,
struct perf_event **group)
{
struct perf_event *iter;
unsigned int rmid;
bool conflict = false;
list_for_each_entry(iter, &cache_groups, hw.cqm_groups_entry) {
rmid = iter->hw.cqm_rmid;
if (__match_event(iter, event)) {
/* All tasks in a group share an RMID */
event->hw.cqm_rmid = rmid;
*group = iter;
return;
}
/*
* We only care about conflicts for events that are
* actually scheduled in (and hence have a valid RMID).
*/
if (__conflict_event(iter, event) && __rmid_valid(rmid))
conflict = true;
}
if (conflict)
rmid = INVALID_RMID;
else
rmid = __get_rmid();
event->hw.cqm_rmid = rmid;
}
static void intel_cqm_event_read(struct perf_event *event)
{
unsigned long flags;
unsigned int rmid;
u64 val;
/*
* Task events are handled by intel_cqm_event_count().
*/
if (event->cpu == -1)
return;
raw_spin_lock_irqsave(&cache_lock, flags);
rmid = event->hw.cqm_rmid;
if (!__rmid_valid(rmid))
goto out;
val = __rmid_read(rmid);
/*
* Ignore this reading on error states and do not update the value.
*/
if (val & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL))
goto out;
local64_set(&event->count, val);
out:
raw_spin_unlock_irqrestore(&cache_lock, flags);
}
static void __intel_cqm_event_count(void *info)
{
struct rmid_read *rr = info;
u64 val;
val = __rmid_read(rr->rmid);
if (val & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL))
return;
atomic64_add(val, &rr->value);
}
static inline bool cqm_group_leader(struct perf_event *event)
{
return !list_empty(&event->hw.cqm_groups_entry);
}
static u64 intel_cqm_event_count(struct perf_event *event)
{
unsigned long flags;
struct rmid_read rr = {
.value = ATOMIC64_INIT(0),
};
/*
* We only need to worry about task events. System-wide events
* are handled like usual, i.e. entirely with
* intel_cqm_event_read().
*/
if (event->cpu != -1)
return __perf_event_count(event);
/*
* Only the group leader gets to report values. This stops us
* reporting duplicate values to userspace, and gives us a clear
* rule for which task gets to report the values.
*
* Note that it is impossible to attribute these values to
* specific packages - we forfeit that ability when we create
* task events.
*/
if (!cqm_group_leader(event))
return 0;
/*
* Notice that we don't perform the reading of an RMID
* atomically, because we can't hold a spin lock across the
* IPIs.
*
* Speculatively perform the read, since @event might be
* assigned a different (possibly invalid) RMID while we're
* busying performing the IPI calls. It's therefore necessary to
* check @event's RMID afterwards, and if it has changed,
* discard the result of the read.
*/
rr.rmid = ACCESS_ONCE(event->hw.cqm_rmid);
if (!__rmid_valid(rr.rmid))
goto out;
on_each_cpu_mask(&cqm_cpumask, __intel_cqm_event_count, &rr, 1);
raw_spin_lock_irqsave(&cache_lock, flags);
if (event->hw.cqm_rmid == rr.rmid)
local64_set(&event->count, atomic64_read(&rr.value));
raw_spin_unlock_irqrestore(&cache_lock, flags);
out:
return __perf_event_count(event);
}
static void intel_cqm_event_start(struct perf_event *event, int mode)
{
struct intel_cqm_state *state = this_cpu_ptr(&cqm_state);
unsigned int rmid = event->hw.cqm_rmid;
unsigned long flags;
if (!(event->hw.cqm_state & PERF_HES_STOPPED))
return;
event->hw.cqm_state &= ~PERF_HES_STOPPED;
raw_spin_lock_irqsave(&state->lock, flags);
if (state->cnt++)
WARN_ON_ONCE(state->rmid != rmid);
else
WARN_ON_ONCE(state->rmid);
state->rmid = rmid;
wrmsrl(MSR_IA32_PQR_ASSOC, state->rmid);
raw_spin_unlock_irqrestore(&state->lock, flags);
}
static void intel_cqm_event_stop(struct perf_event *event, int mode)
{
struct intel_cqm_state *state = this_cpu_ptr(&cqm_state);
unsigned long flags;
if (event->hw.cqm_state & PERF_HES_STOPPED)
return;
event->hw.cqm_state |= PERF_HES_STOPPED;
raw_spin_lock_irqsave(&state->lock, flags);
intel_cqm_event_read(event);
if (!--state->cnt) {
state->rmid = 0;
wrmsrl(MSR_IA32_PQR_ASSOC, 0);
} else {
WARN_ON_ONCE(!state->rmid);
}
raw_spin_unlock_irqrestore(&state->lock, flags);
}
static int intel_cqm_event_add(struct perf_event *event, int mode)
{
unsigned long flags;
unsigned int rmid;
raw_spin_lock_irqsave(&cache_lock, flags);
event->hw.cqm_state = PERF_HES_STOPPED;
rmid = event->hw.cqm_rmid;
if (__rmid_valid(rmid) && (mode & PERF_EF_START))
intel_cqm_event_start(event, mode);
raw_spin_unlock_irqrestore(&cache_lock, flags);
return 0;
}
static void intel_cqm_event_del(struct perf_event *event, int mode)
{
intel_cqm_event_stop(event, mode);
}
static void intel_cqm_event_destroy(struct perf_event *event)
{
struct perf_event *group_other = NULL;
mutex_lock(&cache_mutex);
/*
* If there's another event in this group...
*/
if (!list_empty(&event->hw.cqm_group_entry)) {
group_other = list_first_entry(&event->hw.cqm_group_entry,
struct perf_event,
hw.cqm_group_entry);
list_del(&event->hw.cqm_group_entry);
}
/*
* And we're the group leader..
*/
if (cqm_group_leader(event)) {
/*
* If there was a group_other, make that leader, otherwise
* destroy the group and return the RMID.
*/
if (group_other) {
list_replace(&event->hw.cqm_groups_entry,
&group_other->hw.cqm_groups_entry);
} else {
unsigned int rmid = event->hw.cqm_rmid;
if (__rmid_valid(rmid))
__put_rmid(rmid);
list_del(&event->hw.cqm_groups_entry);
}
}
mutex_unlock(&cache_mutex);
}
static int intel_cqm_event_init(struct perf_event *event)
{
struct perf_event *group = NULL;
bool rotate = false;
if (event->attr.type != intel_cqm_pmu.type)
return -ENOENT;
if (event->attr.config & ~QOS_EVENT_MASK)
return -EINVAL;
/* unsupported modes and filters */
if (event->attr.exclude_user ||
event->attr.exclude_kernel ||
event->attr.exclude_hv ||
event->attr.exclude_idle ||
event->attr.exclude_host ||
event->attr.exclude_guest ||
event->attr.sample_period) /* no sampling */
return -EINVAL;
INIT_LIST_HEAD(&event->hw.cqm_group_entry);
INIT_LIST_HEAD(&event->hw.cqm_groups_entry);
event->destroy = intel_cqm_event_destroy;
mutex_lock(&cache_mutex);
/* Will also set rmid */
intel_cqm_setup_event(event, &group);
if (group) {
list_add_tail(&event->hw.cqm_group_entry,
&group->hw.cqm_group_entry);
} else {
list_add_tail(&event->hw.cqm_groups_entry,
&cache_groups);
/*
* All RMIDs are either in use or have recently been
* used. Kick the rotation worker to clean/free some.
*
* We only do this for the group leader, rather than for
* every event in a group to save on needless work.
*/
if (!__rmid_valid(event->hw.cqm_rmid))
rotate = true;
}
mutex_unlock(&cache_mutex);
if (rotate)
schedule_delayed_work(&intel_cqm_rmid_work, 0);
return 0;
}
EVENT_ATTR_STR(llc_occupancy, intel_cqm_llc, "event=0x01");
EVENT_ATTR_STR(llc_occupancy.per-pkg, intel_cqm_llc_pkg, "1");
EVENT_ATTR_STR(llc_occupancy.unit, intel_cqm_llc_unit, "Bytes");
EVENT_ATTR_STR(llc_occupancy.scale, intel_cqm_llc_scale, NULL);
EVENT_ATTR_STR(llc_occupancy.snapshot, intel_cqm_llc_snapshot, "1");
static struct attribute *intel_cqm_events_attr[] = {
EVENT_PTR(intel_cqm_llc),
EVENT_PTR(intel_cqm_llc_pkg),
EVENT_PTR(intel_cqm_llc_unit),
EVENT_PTR(intel_cqm_llc_scale),
EVENT_PTR(intel_cqm_llc_snapshot),
NULL,
};
static struct attribute_group intel_cqm_events_group = {
.name = "events",
.attrs = intel_cqm_events_attr,
};
PMU_FORMAT_ATTR(event, "config:0-7");
static struct attribute *intel_cqm_formats_attr[] = {
&format_attr_event.attr,
NULL,
};
static struct attribute_group intel_cqm_format_group = {
.name = "format",
.attrs = intel_cqm_formats_attr,
};
static ssize_t
max_recycle_threshold_show(struct device *dev, struct device_attribute *attr,
char *page)
{
ssize_t rv;
mutex_lock(&cache_mutex);
rv = snprintf(page, PAGE_SIZE-1, "%u\n", __intel_cqm_max_threshold);
mutex_unlock(&cache_mutex);
return rv;
}
static ssize_t
max_recycle_threshold_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
unsigned int bytes, cachelines;
int ret;
ret = kstrtouint(buf, 0, &bytes);
if (ret)
return ret;
mutex_lock(&cache_mutex);
__intel_cqm_max_threshold = bytes;
cachelines = bytes / cqm_l3_scale;
/*
* The new maximum takes effect immediately.
*/
if (__intel_cqm_threshold > cachelines)
__intel_cqm_threshold = cachelines;
mutex_unlock(&cache_mutex);
return count;
}
static DEVICE_ATTR_RW(max_recycle_threshold);
static struct attribute *intel_cqm_attrs[] = {
&dev_attr_max_recycle_threshold.attr,
NULL,
};
static const struct attribute_group intel_cqm_group = {
.attrs = intel_cqm_attrs,
};
static const struct attribute_group *intel_cqm_attr_groups[] = {
&intel_cqm_events_group,
&intel_cqm_format_group,
&intel_cqm_group,
NULL,
};
static struct pmu intel_cqm_pmu = {
.hrtimer_interval_ms = RMID_DEFAULT_QUEUE_TIME,
.attr_groups = intel_cqm_attr_groups,
.task_ctx_nr = perf_sw_context,
.event_init = intel_cqm_event_init,
.add = intel_cqm_event_add,
.del = intel_cqm_event_del,
.start = intel_cqm_event_start,
.stop = intel_cqm_event_stop,
.read = intel_cqm_event_read,
.count = intel_cqm_event_count,
};
static inline void cqm_pick_event_reader(int cpu)
{
int phys_id = topology_physical_package_id(cpu);
int i;
for_each_cpu(i, &cqm_cpumask) {
if (phys_id == topology_physical_package_id(i))
return; /* already got reader for this socket */
}
cpumask_set_cpu(cpu, &cqm_cpumask);
}
static void intel_cqm_cpu_prepare(unsigned int cpu)
{
struct intel_cqm_state *state = &per_cpu(cqm_state, cpu);
struct cpuinfo_x86 *c = &cpu_data(cpu);
raw_spin_lock_init(&state->lock);
state->rmid = 0;
state->cnt = 0;
WARN_ON(c->x86_cache_max_rmid != cqm_max_rmid);
WARN_ON(c->x86_cache_occ_scale != cqm_l3_scale);
}
static void intel_cqm_cpu_exit(unsigned int cpu)
{
int phys_id = topology_physical_package_id(cpu);
int i;
/*
* Is @cpu a designated cqm reader?
*/
if (!cpumask_test_and_clear_cpu(cpu, &cqm_cpumask))
return;
for_each_online_cpu(i) {
if (i == cpu)
continue;
if (phys_id == topology_physical_package_id(i)) {
cpumask_set_cpu(i, &cqm_cpumask);
break;
}
}
}
static int intel_cqm_cpu_notifier(struct notifier_block *nb,
unsigned long action, void *hcpu)
{
unsigned int cpu = (unsigned long)hcpu;
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_UP_PREPARE:
intel_cqm_cpu_prepare(cpu);
break;
case CPU_DOWN_PREPARE:
intel_cqm_cpu_exit(cpu);
break;
case CPU_STARTING:
cqm_pick_event_reader(cpu);
break;
}
return NOTIFY_OK;
}
static const struct x86_cpu_id intel_cqm_match[] = {
{ .vendor = X86_VENDOR_INTEL, .feature = X86_FEATURE_CQM_OCCUP_LLC },
{}
};
static int __init intel_cqm_init(void)
{
char *str, scale[20];
int i, cpu, ret;
if (!x86_match_cpu(intel_cqm_match))
return -ENODEV;
cqm_l3_scale = boot_cpu_data.x86_cache_occ_scale;
/*
* It's possible that not all resources support the same number
* of RMIDs. Instead of making scheduling much more complicated
* (where we have to match a task's RMID to a cpu that supports
* that many RMIDs) just find the minimum RMIDs supported across
* all cpus.
*
* Also, check that the scales match on all cpus.
*/
cpu_notifier_register_begin();
for_each_online_cpu(cpu) {
struct cpuinfo_x86 *c = &cpu_data(cpu);
if (c->x86_cache_max_rmid < cqm_max_rmid)
cqm_max_rmid = c->x86_cache_max_rmid;
if (c->x86_cache_occ_scale != cqm_l3_scale) {
pr_err("Multiple LLC scale values, disabling\n");
ret = -EINVAL;
goto out;
}
}
/*
* A reasonable upper limit on the max threshold is the number
* of lines tagged per RMID if all RMIDs have the same number of
* lines tagged in the LLC.
*
* For a 35MB LLC and 56 RMIDs, this is ~1.8% of the LLC.
*/
__intel_cqm_max_threshold =
boot_cpu_data.x86_cache_size * 1024 / (cqm_max_rmid + 1);
snprintf(scale, sizeof(scale), "%u", cqm_l3_scale);
str = kstrdup(scale, GFP_KERNEL);
if (!str) {
ret = -ENOMEM;
goto out;
}
event_attr_intel_cqm_llc_scale.event_str = str;
ret = intel_cqm_setup_rmid_cache();
if (ret)
goto out;
for_each_online_cpu(i) {
intel_cqm_cpu_prepare(i);
cqm_pick_event_reader(i);
}
__perf_cpu_notifier(intel_cqm_cpu_notifier);
ret = perf_pmu_register(&intel_cqm_pmu, "intel_cqm", -1);
if (ret)
pr_err("Intel CQM perf registration failed: %d\n", ret);
else
pr_info("Intel CQM monitoring enabled\n");
out:
cpu_notifier_register_done();
return ret;
}
device_initcall(intel_cqm_init);