1 files changed, 311 insertions, 0 deletions

diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c
new file mode 100644
index 000000000000..e6ecbb2b8698
--- /dev/null
+++ b/kernel/sched/pelt.c
@@ -0,0 +1,311 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Per Entity Load Tracking
+ *
+ *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ *
+ *  Interactivity improvements by Mike Galbraith
+ *  (C) 2007 Mike Galbraith <efault@gmx.de>
+ *
+ *  Various enhancements by Dmitry Adamushko.
+ *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
+ *
+ *  Group scheduling enhancements by Srivatsa Vaddagiri
+ *  Copyright IBM Corporation, 2007
+ *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
+ *
+ *  Scaled math optimizations by Thomas Gleixner
+ *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
+ *
+ *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
+ *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
+ *
+ *  Move PELT related code from fair.c into this pelt.c file
+ *  Author: Vincent Guittot <vincent.guittot@linaro.org>
+ */
+
+#include <linux/sched.h>
+#include "sched.h"
+#include "sched-pelt.h"
+#include "pelt.h"
+
+/*
+ * Approximate:
+ *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
+ */
+static u64 decay_load(u64 val, u64 n)
+{
+        unsigned int local_n;
+
+        if (unlikely(n > LOAD_AVG_PERIOD * 63))
+                return 0;
+
+        /* after bounds checking we can collapse to 32-bit */
+        local_n = n;
+
+        /*
+         * As y^PERIOD = 1/2, we can combine
+         *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
+         * With a look-up table which covers y^n (n<PERIOD)
+         *
+         * To achieve constant time decay_load.
+         */
+        if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
+                val >>= local_n / LOAD_AVG_PERIOD;
+                local_n %= LOAD_AVG_PERIOD;
+        }
+
+        val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
+        return val;
+}
+
+static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3)
+{
+        u32 c1, c2, c3 = d3; /* y^0 == 1 */
+
+        /*
+         * c1 = d1 y^p
+         */
+        c1 = decay_load((u64)d1, periods);
+
+        /*
+         *            p-1
+         * c2 = 1024 \Sum y^n
+         *            n=1
+         *
+         *              inf        inf
+         *    = 1024 ( \Sum y^n - \Sum y^n - y^0 )
+         *              n=0        n=p
+         */
+        c2 = LOAD_AVG_MAX - decay_load(LOAD_AVG_MAX, periods) - 1024;
+
+        return c1 + c2 + c3;
+}
+
+#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
+
+/*
+ * Accumulate the three separate parts of the sum; d1 the remainder
+ * of the last (incomplete) period, d2 the span of full periods and d3
+ * the remainder of the (incomplete) current period.
+ *
+ *           d1          d2           d3
+ *           ^           ^            ^
+ *           |           |            |
+ *         |<->|<----------------->|<--->|
+ * ... |---x---|------| ... |------|-----x (now)
+ *
+ *                           p-1
+ * u' = (u + d1) y^p + 1024 \Sum y^n + d3 y^0
+ *                           n=1
+ *
+ *    = u y^p +                                 (Step 1)
+ *
+ *                     p-1
+ *      d1 y^p + 1024 \Sum y^n + d3 y^0         (Step 2)
+ *                     n=1
+ */
+static __always_inline u32
+accumulate_sum(u64 delta, int cpu, struct sched_avg *sa,
+               unsigned long load, unsigned long runnable, int running)
+{
+        unsigned long scale_freq, scale_cpu;
+        u32 contrib = (u32)delta; /* p == 0 -> delta < 1024 */
+        u64 periods;
+
+        scale_freq = arch_scale_freq_capacity(cpu);
+        scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
+
+        delta += sa->period_contrib;
+        periods = delta / 1024; /* A period is 1024us (~1ms) */
+
+        /*
+         * Step 1: decay old *_sum if we crossed period boundaries.
+         */
+        if (periods) {
+                sa->load_sum = decay_load(sa->load_sum, periods);
+                sa->runnable_load_sum =
+                        decay_load(sa->runnable_load_sum, periods);
+                sa->util_sum = decay_load((u64)(sa->util_sum), periods);
+
+                /*
+                 * Step 2
+                 */
+                delta %= 1024;
+                contrib = __accumulate_pelt_segments(periods,
+                                1024 - sa->period_contrib, delta);
+        }
+        sa->period_contrib = delta;
+
+        contrib = cap_scale(contrib, scale_freq);
+        if (load)
+                sa->load_sum += load * contrib;
+        if (runnable)
+                sa->runnable_load_sum += runnable * contrib;
+        if (running)
+                sa->util_sum += contrib * scale_cpu;
+
+        return periods;
+}
+
+/*
+ * We can represent the historical contribution to runnable average as the
+ * coefficients of a geometric series.  To do this we sub-divide our runnable
+ * history into segments of approximately 1ms (1024us); label the segment that
+ * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
+ *
+ * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
+ *      p0            p1           p2
+ *     (now)       (~1ms ago)  (~2ms ago)
+ *
+ * Let u_i denote the fraction of p_i that the entity was runnable.
+ *
+ * We then designate the fractions u_i as our co-efficients, yielding the
+ * following representation of historical load:
+ *   u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
+ *
+ * We choose y based on the with of a reasonably scheduling period, fixing:
+ *   y^32 = 0.5
+ *
+ * This means that the contribution to load ~32ms ago (u_32) will be weighted
+ * approximately half as much as the contribution to load within the last ms
+ * (u_0).
+ *
+ * When a period "rolls over" and we have new u_0`, multiplying the previous
+ * sum again by y is sufficient to update:
+ *   load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
+ *            = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
+ */
+static __always_inline int
+___update_load_sum(u64 now, int cpu, struct sched_avg *sa,
+                  unsigned long load, unsigned long runnable, int running)
+{
+        u64 delta;
+
+        delta = now - sa->last_update_time;
+        /*
+         * This should only happen when time goes backwards, which it
+         * unfortunately does during sched clock init when we swap over to TSC.
+         */
+        if ((s64)delta < 0) {
+                sa->last_update_time = now;
+                return 0;
+        }
+
+        /*
+         * Use 1024ns as the unit of measurement since it's a reasonable
+         * approximation of 1us and fast to compute.
+         */
+        delta >>= 10;
+        if (!delta)
+                return 0;
+
+        sa->last_update_time += delta << 10;
+
+        /*
+         * running is a subset of runnable (weight) so running can't be set if
+         * runnable is clear. But there are some corner cases where the current
+         * se has been already dequeued but cfs_rq->curr still points to it.
+         * This means that weight will be 0 but not running for a sched_entity
+         * but also for a cfs_rq if the latter becomes idle. As an example,
+         * this happens during idle_balance() which calls
+         * update_blocked_averages()
+         */
+        if (!load)
+                runnable = running = 0;
+
+        /*
+         * Now we know we crossed measurement unit boundaries. The *_avg
+         * accrues by two steps:
+         *
+         * Step 1: accumulate *_sum since last_update_time. If we haven't
+         * crossed period boundaries, finish.
+         */
+        if (!accumulate_sum(delta, cpu, sa, load, runnable, running))
+                return 0;
+
+        return 1;
+}
+
+static __always_inline void
+___update_load_avg(struct sched_avg *sa, unsigned long load, unsigned long runnable)
+{
+        u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
+
+        /*
+         * Step 2: update *_avg.
+         */
+        sa->load_avg = div_u64(load * sa->load_sum, divider);
+        sa->runnable_load_avg = div_u64(runnable * sa->runnable_load_sum, divider);
+        sa->util_avg = sa->util_sum / divider;
+}
+
+/*
+ * sched_entity:
+ *
+ *   task:
+ *     se_runnable() == se_weight()
+ *
+ *   group: [ see update_cfs_group() ]
+ *     se_weight()   = tg->weight * grq->load_avg / tg->load_avg
+ *     se_runnable() = se_weight(se) * grq->runnable_load_avg / grq->load_avg
+ *
+ *   load_sum := runnable_sum
+ *   load_avg = se_weight(se) * runnable_avg
+ *
+ *   runnable_load_sum := runnable_sum
+ *   runnable_load_avg = se_runnable(se) * runnable_avg
+ *
+ * XXX collapse load_sum and runnable_load_sum
+ *
+ * cfq_rq:
+ *
+ *   load_sum = \Sum se_weight(se) * se->avg.load_sum
+ *   load_avg = \Sum se->avg.load_avg
+ *
+ *   runnable_load_sum = \Sum se_runnable(se) * se->avg.runnable_load_sum
+ *   runnable_load_avg = \Sum se->avg.runable_load_avg
+ */
+
+int __update_load_avg_blocked_se(u64 now, int cpu, struct sched_entity *se)
+{
+        if (entity_is_task(se))
+                se->runnable_weight = se->load.weight;
+
+        if (___update_load_sum(now, cpu, &se->avg, 0, 0, 0)) {
+                ___update_load_avg(&se->avg, se_weight(se), se_runnable(se));
+                return 1;
+        }
+
+        return 0;
+}
+
+int __update_load_avg_se(u64 now, int cpu, struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+        if (entity_is_task(se))
+                se->runnable_weight = se->load.weight;
+
+        if (___update_load_sum(now, cpu, &se->avg, !!se->on_rq, !!se->on_rq,
+                                cfs_rq->curr == se)) {
+
+                ___update_load_avg(&se->avg, se_weight(se), se_runnable(se));
+                cfs_se_util_change(&se->avg);
+                return 1;
+        }
+
+        return 0;
+}
+
+int __update_load_avg_cfs_rq(u64 now, int cpu, struct cfs_rq *cfs_rq)
+{
+        if (___update_load_sum(now, cpu, &cfs_rq->avg,
+                                scale_load_down(cfs_rq->load.weight),
+                                scale_load_down(cfs_rq->runnable_weight),
+                                cfs_rq->curr != NULL)) {
+
+                ___update_load_avg(&cfs_rq->avg, 1, 1);
+                return 1;
+        }
+
+        return 0;
+}