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hv: sched: add four parameters for BVT scheduler 

Per BVT (Borrowed Virtual Time) scheduler design, following per thread
parameters are required to tune scheduling behaviour.
- weight
  The time sharing of a thread on CPU.
- warp
  Boost value of virtual time of a thread (time borrowed from future) to
  reduce Effective Virtual Time to prioritize the thread.
- warp_limit
  Max warp time in one warp.
- unwarp_period
  Min unwarp time after a warp.

As of now, only weight is in use to tune virtual time ratio of VCPU
threads from different VMs. Others parameters are for future extension.

Tracked-On: #8500
Reviewed-by: Junjie Mao <junjie.mao@intel.com>
Signed-off-by: Qiang Zhang <qiang4.zhang@intel.com>
This commit is contained in:
Qiang Zhang 2023-08-31 14:05:54 +08:00 committed by acrnsi-robot
parent 04a4f31d28
commit 79b91b339b
1 changed files with 41 additions and 6 deletions
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47
hypervisor/common/sched_bvt.c
View File

@ -9,18 +9,49 @@
#include <schedule.h>
#include <ticks.h>
#define BVT_MCU_MS 1U
#define BVT_MCU_MS 1U
/* context switch allowance */
#define BVT_CSA_MCU 5U
#define BVT_CSA_MCU 5U
/*
* limit the weight range to [1, 128]. It's enough to allocate CPU resources
* for different types of vCPUs
*/
#define BVT_WEIGHT_MIN 1U
#define BVT_WEIGHT_MAX 128U
/*
* the VT (Virtual Time) ratio is proportional to 1 / weight and making the VT
* ratio an integer will ease translation between virtual time and physical
* time.
* Max (theoretical VT ratio - actual VT ratio) is
* 1 (< 1 because of integer round down).
* The minimum total VT ratios of VCPUs (at least two) is
* 2 * 8 (Min per-vcpu VT ratio)
* So the max VT ratio share error is about 1/16.
* To reduce it, we can enlarge the BVT_VT_RATIO_MIN.
* However increasing VT ratio will reduce the total time needed to overflow
* AVT. AVT is of type int64_t. The max VT ratio is 1024. MCU is 1 ms.
* So the time to overflow AVT is about:
* 2^63 / (1024 * 1000) s, i.e. ~= 9 * 10^12(s) ~= 10^8 day
* It's so large that we can ignore the AVT overflow case.
*/
#define BVT_VT_RATIO_MIN 8U
#define BVT_VT_RATIO_MAX (BVT_WEIGHT_MAX * BVT_VT_RATIO_MIN / BVT_WEIGHT_MIN)
struct sched_bvt_data {
/* keep list as the first item */
struct list_head list;
/* minimum charging unit in cycles */
uint64_t mcu;
/* a thread receives a share of cpu in proportion to its weight */
uint16_t weight;
uint8_t weight;
/* virtual time advance variable, proportional to 1 / weight */
uint64_t vt_ratio;
bool warp_on;
int32_t warp_value;
uint32_t warp_limit;
uint32_t unwarp_period;
/* actual virtual time in units of mcu */
int64_t avt;
/* effective virtual time in units of mcu */
@ -168,15 +199,19 @@ static void sched_bvt_deinit(struct sched_control *ctl)
del_timer(&bvt_ctl->tick_timer);
}
static void sched_bvt_init_data(struct thread_object *obj, __unused struct sched_params * params)
static void sched_bvt_init_data(struct thread_object *obj, struct sched_params * params)
{
struct sched_bvt_data *data;
data = (struct sched_bvt_data *)obj->data;
INIT_LIST_HEAD(&data->list);
data->mcu = BVT_MCU_MS * TICKS_PER_MS;
/* TODO: virtual time advance ratio should be proportional to weight. */
data->vt_ratio = 1U;
data->weight = clamp(params->bvt_weight, BVT_WEIGHT_MIN, BVT_WEIGHT_MAX);
data->warp_value = params->bvt_warp_value;
data->warp_limit = params->bvt_warp_limit;
data->unwarp_period = params->bvt_unwarp_period;
data->warp_on = false; /* warp disabled by default */
data->vt_ratio = BVT_VT_RATIO_MAX / data->weight;
data->residual = 0U;
}