Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752811AbcD2EqZ (ORCPT ); Fri, 29 Apr 2016 00:46:25 -0400 Received: from mail-pf0-f177.google.com ([209.85.192.177]:33722 "EHLO mail-pf0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750971AbcD2EqW (ORCPT ); Fri, 29 Apr 2016 00:46:22 -0400 From: David Carrillo-Cisneros To: Peter Zijlstra , Alexander Shishkin , Arnaldo Carvalho de Melo , Ingo Molnar Cc: Vikas Shivappa , Matt Fleming , Tony Luck , Stephane Eranian , Paul Turner , David Carrillo-Cisneros , x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 03/32] perf/x86/intel/cqm: remove all code for rotation of RMIDs Date: Thu, 28 Apr 2016 21:43:09 -0700 Message-Id: <1461905018-86355-4-git-send-email-davidcc@google.com> X-Mailer: git-send-email 2.8.0.rc3.226.g39d4020 In-Reply-To: <1461905018-86355-1-git-send-email-davidcc@google.com> References: <1461905018-86355-1-git-send-email-davidcc@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 12287 Lines: 433 In preparation for future patches that will introduce a per-package rotation of RMIDs. The new rotation logic follows the same ideas as the present rotation logic being removed but takes advantage of the per-package RMID design and a more detailed bookkeeping to guarantee to meet user SLOs. It also avoid IPIs, and does not keep an unused rotation RMID in some cases (as present version does). Reviewed-by: Stephane Eranian Signed-off-by: David Carrillo-Cisneros --- arch/x86/events/intel/cqm.c | 371 -------------------------------------------- 1 file changed, 371 deletions(-) diff --git a/arch/x86/events/intel/cqm.c b/arch/x86/events/intel/cqm.c index a3fde49..3c1e247 100644 --- a/arch/x86/events/intel/cqm.c +++ b/arch/x86/events/intel/cqm.c @@ -312,42 +312,6 @@ struct rmid_read { static void __intel_cqm_event_count(void *info); /* - * 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 = { - .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 <= @@ -364,44 +328,6 @@ 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; - } -} - -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; - - 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. * @@ -411,291 +337,8 @@ static bool intel_cqm_sched_in_event(u32 rmid) */ #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 (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); -} - -/* - * Attempt to rotate the groups and assign new 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 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(); - - 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. * @@ -937,7 +580,6 @@ 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; if (event->attr.type != intel_cqm_pmu.type) return -ENOENT; @@ -971,23 +613,10 @@ static int intel_cqm_event_init(struct perf_event *event) } 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; } -- 2.8.0.rc3.226.g39d4020