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