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126 lines
3.9 KiB
126 lines
3.9 KiB
#pragma once
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#include <stdatomic.h>
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#include <stdbool.h>
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#include <stdint.h>
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#include <unistd.h>
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#include "debuglog.h"
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#include "client_socket.h"
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#define ADMISSIONS_CONTROL_GRANULARITY 1000000
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/*
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* Unitless estimate of the instantaneous fraction of system capacity required to complete all previously
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* admitted work. This is used to calculate free capacity as part of admissions control
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*
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* The estimated requirements of a single admitted request is calculated as
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* estimated execution time (cycles) / relative deadline (cycles)
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*
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* These estimates are incremented on request acceptance and decremented on request completion (either
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* success or failure)
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*/
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extern _Atomic uint64_t admissions_control_admitted;
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extern uint64_t admissions_control_capacity;
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extern const double admissions_control_overhead;
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static inline void
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admissions_control_initialize()
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{
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#ifdef ADMISSIONS_CONTROL
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atomic_init(&admissions_control_admitted, 0);
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admissions_control_capacity = runtime_worker_threads_count * ADMISSIONS_CONTROL_GRANULARITY
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* ((double)1.0 - admissions_control_overhead);
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#endif
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}
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static inline void
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admissions_control_add(uint64_t admissions_estimate)
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{
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#ifdef ADMISSIONS_CONTROL
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assert(admissions_estimate > 0);
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atomic_fetch_add(&admissions_control_admitted, admissions_estimate);
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#ifdef LOG_ADMISSIONS_CONTROL
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debuglog("Runtime Admitted: %lu / %lu\n", admissions_control_admitted, admissions_control_capacity);
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#endif
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#endif /* ADMISSIONS_CONTROL */
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}
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static inline void
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admissions_control_substract(uint64_t admissions_estimate)
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{
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#ifdef ADMISSIONS_CONTROL
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/* Assumption: Should never underflow */
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if (unlikely(admissions_estimate > admissions_control_admitted)) panic("Admissions Estimate underflow\n");
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atomic_fetch_sub(&admissions_control_admitted, admissions_estimate);
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#ifdef LOG_ADMISSIONS_CONTROL
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debuglog("Runtime Admitted: %lu / %lu\n", admissions_control_admitted, admissions_control_capacity);
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#endif
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#endif /* ADMISSIONS_CONTROL */
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}
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static inline uint64_t
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admissions_control_calculate_estimate(uint64_t estimated_execution, uint64_t relative_deadline)
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{
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#ifdef ADMISSIONS_CONTROL
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assert(relative_deadline != 0);
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uint64_t admissions_estimate = (estimated_execution * (uint64_t)ADMISSIONS_CONTROL_GRANULARITY)
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/ relative_deadline;
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if (admissions_estimate == 0)
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panic("Ratio of Deadline to Execution time cannot exceed %d\n", ADMISSIONS_CONTROL_GRANULARITY);
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return admissions_estimate;
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#else
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return 0;
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#endif
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}
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static inline uint64_t
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admissions_control_calculate_estimate_us(uint32_t estimated_execution_us, uint32_t relative_deadline_us)
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{
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#ifdef ADMISSIONS_CONTROL
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assert(relative_deadline_us != 0);
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return (uint64_t)((uint64_t)(estimated_execution_us * ADMISSIONS_CONTROL_GRANULARITY)) / relative_deadline_us;
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#else
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return 0;
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#endif
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}
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static inline void
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admissions_control_log_decision(uint64_t admissions_estimate, bool admitted)
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{
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#ifdef LOG_ADMISSIONS_CONTROL
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debuglog("Admitted: %lu, Capacity: %lu, Estimate: %lu, Admitted? %s\n", admissions_control_admitted,
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admissions_control_capacity, admissions_estimate, admitted ? "yes" : "no");
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#endif /* LOG_ADMISSIONS_CONTROL */
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}
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static inline uint64_t
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admissions_control_decide(uint64_t admissions_estimate)
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{
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uint64_t work_admitted = 1; /* Nominal non-zero value in case admissions control is disabled */
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#ifdef ADMISSIONS_CONTROL
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if (unlikely(admissions_estimate == 0)) panic("Admissions estimate should never be zero");
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uint64_t total_admitted = atomic_load(&admissions_control_admitted);
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if (total_admitted + admissions_estimate >= admissions_control_capacity) {
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admissions_control_log_decision(admissions_estimate, false);
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work_admitted = 0;
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} else {
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admissions_control_log_decision(admissions_estimate, true);
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admissions_control_add(admissions_estimate);
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work_admitted = admissions_estimate;
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}
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#endif /* ADMISSIONS_CONTROL */
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return work_admitted;
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}
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