Message-Id: <1481929988-31569-3-git-send-email-vikas.shivappa@linux.intel.com>
Date:   Fri, 16 Dec 2016 15:12:56 -0800
From:   Vikas Shivappa <vikas.shivappa@...ux.intel.com>
To:     vikas.shivappa@...el.com, vikas.shivappa@...ux.intel.com
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, tglx@...utronix.de,
        peterz@...radead.org, ravi.v.shankar@...el.com,
        tony.luck@...el.com, fenghua.yu@...el.com, andi.kleen@...el.com,
        davidcc@...gle.com, eranian@...gle.com, hpa@...or.com
Subject: [PATCH 02/14] x86/cqm: Remove cqm recycling/conflict handling

From: David Carrillo-Cisneros <davidcc@...gle.com>

We only supported global RMIDs till now and not per-pkg RMIDs and hence
the RMIDs would not scale and we would more easily run out of RMIDs.
When we run out of RMIDs we did RMID recycling and ended up in several
issues some of which listed below and complications which may outweigh
benefits.

RMID recycling 'steals' RMID from an event x that is being monitored and
gives it to an event y that is also being monitored.
- This does not guarantee that we get the correct data for both the events
as there is always times when the events are not being monitored. Hence
there could be incorrect data to the user. The extent of error is
arbitrary and unknown as we cannot measure how much of the occupancy we
missed.
- It complicated the usage of RMIDs, reading of data, MBM counting
a lot because when reading the counters we had to keep a history of
previous counts and also make sure that no one has stolen that RMID we
want to use. All this had a lot of code foot print.
- When a process changes RMID it is
no more tracking the old cache fills it had in the old RMID - so we are
not even guaranteeing the data to be correct for the time its monitored
if it had and RMID for almost all of the time.
- There was inconsistent data in the current patch due to the way RMID
was recycled, we ended up stealing RMIDs from monitored events before
using the freed RMIDs in the limbo list. This led to 0 counts as soon as
one runs out of RMIDs in the lifetime of systemboot which almost makes
the feature unusable. Also the state transitions were messy.

This patch removes RMID recycling and just
throw error when there are no more RMIDs to monitor. H/w provides ~4
RMIDs per logical processor on each package and if we use all of them
and use only when the tasks are scheduled on the pkgs,
the problem of scarcity can be mitigated.

The conflict handling is also removed as it resulted in a lot of
inconsistent data when different kinds of events like systemwide,cgroup
and task were monitored together.

David's original patch modified by Vikas<vikas.shivappa@...ux.intel.com>
to only remove recycling parts from code and edit commit message.

Tests: The cqm should either gives correct numbers for task events
or just throw error that its run out of RMIDs.

Signed-off-by: Vikas Shivappa <vikas.shivappa@...ux.intel.com>
---
 arch/x86/events/intel/cqm.c | 647 ++------------------------------------------
 1 file changed, 30 insertions(+), 617 deletions(-)

diff --git a/arch/x86/events/intel/cqm.c b/arch/x86/events/intel/cqm.c
index 0c45cc8..badeaf4 100644
--- a/arch/x86/events/intel/cqm.c
+++ b/arch/x86/events/intel/cqm.c
@@ -4,6 +4,8 @@
  * Based very, very heavily on work by Peter Zijlstra.
  */
 
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
 #include <linux/perf_event.h>
 #include <linux/slab.h>
 #include <asm/cpu_device_id.h>
@@ -18,6 +20,7 @@
  * Guaranteed time in ms as per SDM where MBM counters will not overflow.
  */
 #define MBM_CTR_OVERFLOW_TIME	1000
+#define RMID_DEFAULT_QUEUE_TIME	250
 
 static u32 cqm_max_rmid = -1;
 static unsigned int cqm_l3_scale; /* supposedly cacheline size */
@@ -91,15 +94,6 @@ struct sample {
 #define QOS_MBM_TOTAL_EVENT_ID	0x02
 #define QOS_MBM_LOCAL_EVENT_ID	0x03
 
-/*
- * 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 u32 intel_cqm_rotation_rmid;
-
 #define INVALID_RMID		(-1)
 
 /*
@@ -112,7 +106,7 @@ struct sample {
  */
 static inline bool __rmid_valid(u32 rmid)
 {
-	if (!rmid || rmid == INVALID_RMID)
+	if (!rmid || rmid > cqm_max_rmid)
 		return false;
 
 	return true;
@@ -137,8 +131,7 @@ static u64 __rmid_read(u32 rmid)
 }
 
 enum rmid_recycle_state {
-	RMID_YOUNG = 0,
-	RMID_AVAILABLE,
+	RMID_AVAILABLE = 0,
 	RMID_DIRTY,
 };
 
@@ -228,7 +221,7 @@ static void __put_rmid(u32 rmid)
 	entry = __rmid_entry(rmid);
 
 	entry->queue_time = jiffies;
-	entry->state = RMID_YOUNG;
+	entry->state = RMID_DIRTY;
 
 	list_add_tail(&entry->list, &cqm_rmid_limbo_lru);
 }
@@ -281,10 +274,6 @@ static int intel_cqm_setup_rmid_cache(void)
 	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:
@@ -343,92 +332,6 @@ static inline struct perf_cgroup *event_to_cgroup(struct perf_event *event)
 }
 #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 {
 	u32 rmid;
 	u32 evt_type;
@@ -458,461 +361,14 @@ static void cqm_mask_call(struct rmid_read *rr)
 }
 
 /*
- * Exchange the RMID of a group of events.
- */
-static u32 intel_cqm_xchg_rmid(struct perf_event *group, u32 rmid)
-{
-	struct perf_event *event;
-	struct list_head *head = &group->hw.cqm_group_entry;
-	u32 old_rmid = group->hw.cqm_rmid;
-
-	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 = {
-			.rmid = old_rmid,
-			.evt_type = group->attr.config,
-			.value = ATOMIC64_INIT(0),
-		};
-
-		cqm_mask_call(&rr);
-		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);
-
-	/*
-	 * If the allocation is for mbm, init the mbm stats.
-	 * Need to check if each event in the group is mbm event
-	 * because there could be multiple type of events in the same group.
-	 */
-	if (__rmid_valid(rmid)) {
-		event = group;
-		if (is_mbm_event(event->attr.config))
-			init_mbm_sample(rmid, event->attr.config);
-
-		list_for_each_entry(event, head, hw.cqm_group_entry) {
-			if (is_mbm_event(event->attr.config))
-				init_mbm_sample(rmid, event->attr.config);
-		}
-	}
-
-	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(u32 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;
-	u32 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;
-	u32 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);
-}
-
 static u64 update_sample(unsigned int rmid, u32 evt_type, int first)
 {
 	struct sample *mbm_current;
@@ -984,11 +440,10 @@ static void init_mbm_sample(u32 rmid, u32 evt_type)
  *
  * If we're part of a group, we use the group's RMID.
  */
-static void intel_cqm_setup_event(struct perf_event *event,
+static int intel_cqm_setup_event(struct perf_event *event,
 				  struct perf_event **group)
 {
 	struct perf_event *iter;
-	bool conflict = false;
 	u32 rmid;
 
 	event->hw.is_group_event = false;
@@ -1001,26 +456,24 @@ static void intel_cqm_setup_event(struct perf_event *event,
 			*group = iter;
 			if (is_mbm_event(event->attr.config) && __rmid_valid(rmid))
 				init_mbm_sample(rmid, event->attr.config);
-			return;
+			return 0;
 		}
 
-		/*
-		 * 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();
+	rmid = __get_rmid();
+
+	if (!__rmid_valid(rmid)) {
+		pr_info("out of RMIDs\n");
+		return -EINVAL;
+	}
 
 	if (is_mbm_event(event->attr.config) && __rmid_valid(rmid))
 		init_mbm_sample(rmid, event->attr.config);
 
 	event->hw.cqm_rmid = rmid;
+
+	return 0;
 }
 
 static void intel_cqm_event_read(struct perf_event *event)
@@ -1166,7 +619,6 @@ static void mbm_hrtimer_init(void)
 
 static u64 intel_cqm_event_count(struct perf_event *event)
 {
-	unsigned long flags;
 	struct rmid_read rr = {
 		.evt_type = event->attr.config,
 		.value = ATOMIC64_INIT(0),
@@ -1206,24 +658,11 @@ static u64 intel_cqm_event_count(struct perf_event *event)
 	 * 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;
-
 	cqm_mask_call(&rr);
+	local64_set(&event->count, atomic64_read(&rr.value));
 
-	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);
 }
@@ -1238,34 +677,16 @@ static void intel_cqm_event_start(struct perf_event *event, int mode)
 
 	event->hw.cqm_state &= ~PERF_HES_STOPPED;
 
-	if (state->rmid_usecnt++) {
-		if (!WARN_ON_ONCE(state->rmid != rmid))
-			return;
-	} else {
-		WARN_ON_ONCE(state->rmid);
-	}
-
 	state->rmid = rmid;
 	wrmsr(MSR_IA32_PQR_ASSOC, rmid, state->closid);
 }
 
 static void intel_cqm_event_stop(struct perf_event *event, int mode)
 {
-	struct intel_pqr_state *state = this_cpu_ptr(&pqr_state);
-
 	if (event->hw.cqm_state & PERF_HES_STOPPED)
 		return;
 
 	event->hw.cqm_state |= PERF_HES_STOPPED;
-
-	intel_cqm_event_read(event);
-
-	if (!--state->rmid_usecnt) {
-		state->rmid = 0;
-		wrmsr(MSR_IA32_PQR_ASSOC, 0, state->closid);
-	} else {
-		WARN_ON_ONCE(!state->rmid);
-	}
 }
 
 static int intel_cqm_event_add(struct perf_event *event, int mode)
@@ -1342,8 +763,8 @@ static void intel_cqm_event_destroy(struct perf_event *event)
 static int intel_cqm_event_init(struct perf_event *event)
 {
 	struct perf_event *group = NULL;
-	bool rotate = false;
 	unsigned long flags;
+	int ret = 0;
 
 	if (event->attr.type != intel_cqm_pmu.type)
 		return -ENOENT;
@@ -1373,46 +794,36 @@ static int intel_cqm_event_init(struct perf_event *event)
 
 	mutex_lock(&cache_mutex);
 
+	/* Will also set rmid, return error on RMID not being available*/
+	if (intel_cqm_setup_event(event, &group)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
 	/*
 	 * Start the mbm overflow timers when the first event is created.
 	*/
 	if (mbm_enabled && list_empty(&cache_groups))
 		mbm_start_timers();
 
-	/* Will also set rmid */
-	intel_cqm_setup_event(event, &group);
-
 	/*
 	* Hold the cache_lock as mbm timer handlers be
 	* scanning the list of events.
 	*/
 	raw_spin_lock_irqsave(&cache_lock, flags);
 
-	if (group) {
+	if (group)
 		list_add_tail(&event->hw.cqm_group_entry,
 			      &group->hw.cqm_group_entry);
-	} else {
+	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;
-	}
-
 	raw_spin_unlock_irqrestore(&cache_lock, flags);
+out:
 	mutex_unlock(&cache_mutex);
 
-	if (rotate)
-		schedule_delayed_work(&intel_cqm_rmid_work, 0);
-
-	return 0;
+	return ret;
 }
 
 EVENT_ATTR_STR(llc_occupancy, intel_cqm_llc, "event=0x01");
@@ -1706,6 +1117,8 @@ static int __init intel_cqm_init(void)
 	__intel_cqm_max_threshold =
 		boot_cpu_data.x86_cache_size * 1024 / (cqm_max_rmid + 1);
 
+	__intel_cqm_threshold = __intel_cqm_max_threshold / cqm_l3_scale;
+
 	snprintf(scale, sizeof(scale), "%u", cqm_l3_scale);
 	str = kstrdup(scale, GFP_KERNEL);
 	if (!str) {
-- 
1.9.1

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