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https://github.com/projectacrn/acrn-hypervisor.git
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a7563cb9bd
BVT (Borrowed virtual time) scheduler is used to schedule vCPUs on pCPU.
It has the concept of virtual time, vCPU with earliset virtual time is
dispatched first.
Main concepts:
tick timer:
a period tick is used to measure the physcial time in units of MCU
(minimum charing unit).
runqueue:
thread in the runqueue is ordered by virtual time.
weight:
each thread receives a share of the pCPU in proportion to its
weight.
context switch allowance:
the physcial time by which the current thread is allowed to advance
beyond the next runnable thread.
warp:
a thread with warp enabled will have a change to minus a value (Wi)
from virtual time to achieve higher priority.
virtual time:
AVT: actual virtual time, advance in proportional to weight.
EVT: effective virtual time.
EVT <- AVT - ( warp ? Wi : 0 )
SVT: scheduler virtual time, the minimum AVT in the runqueue.
Tracked-On: #4410
Signed-off-by: Conghui Chen <conghui.chen@intel.com>
Signed-off-by: Shuo A Liu <shuo.a.liu@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>
68 lines
1.5 KiB
C
68 lines
1.5 KiB
C
/*
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* Copyright (C) 2020 Intel Corporation. All rights reserved.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#include <list.h>
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#include <per_cpu.h>
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#include <schedule.h>
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#define BVT_MCU_MS 1U
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/* context switch allowance */
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#define BVT_CSA_MCU 5U
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struct sched_bvt_data {
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/* keep list as the first item */
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struct list_head list;
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/* minimum charging unit in cycles */
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uint64_t mcu;
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/* a thread receives a share of cpu in proportion to its weight */
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uint16_t weight;
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/* virtual time advance variable, proportional to 1 / weight */
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uint64_t vt_ratio;
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/* the count down number of mcu until reschedule should take place */
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uint64_t run_countdown;
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/* actual virtual time in units of mcu */
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int64_t avt;
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/* effective virtual time in units of mcu */
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int64_t evt;
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uint64_t start_tsc;
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};
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static int sched_bvt_init(__unused struct sched_control *ctl)
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{
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return 0;
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}
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static void sched_bvt_deinit(__unused struct sched_control *ctl)
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{
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}
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static void sched_bvt_init_data(__unused struct thread_object *obj)
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{
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}
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static struct thread_object *sched_bvt_pick_next(__unused struct sched_control *ctl)
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{
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return NULL;
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}
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static void sched_bvt_sleep(__unused struct thread_object *obj)
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{
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}
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static void sched_bvt_wake(__unused struct thread_object *obj)
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{
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}
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struct acrn_scheduler sched_bvt = {
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.name = "sched_bvt",
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.init = sched_bvt_init,
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.init_data = sched_bvt_init_data,
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.pick_next = sched_bvt_pick_next,
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.sleep = sched_bvt_sleep,
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.wake = sched_bvt_wake,
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.deinit = sched_bvt_deinit,
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};
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