5f4ed3f058
Add a function rte_rand_max() which generates an uniformly distributed pseudo-random number less than a user-specified upper bound. The commonly used pattern rte_rand() % SOME_VALUE creates biased results (as in some values in the range are more frequently occurring than others) if SOME_VALUE is not a power of 2. Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com> Acked-by: Bruce Richardson <bruce.richardson@intel.com>
93 lines
1.8 KiB
C
93 lines
1.8 KiB
C
/* SPDX-License-Identifier: BSD-3-Clause
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* Copyright(c) 2019 Ericsson AB
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*/
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#include <inttypes.h>
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#include <stdio.h>
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#include <rte_common.h>
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#include <rte_cycles.h>
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#include <rte_random.h>
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#include "test.h"
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static volatile uint64_t vsum;
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#define ITERATIONS (100000000)
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#define BEST_CASE_BOUND (1<<16)
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#define WORST_CASE_BOUND (BEST_CASE_BOUND + 1)
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enum rand_type {
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rand_type_64,
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rand_type_bounded_best_case,
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rand_type_bounded_worst_case
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};
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static const char *
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rand_type_desc(enum rand_type rand_type)
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{
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switch (rand_type) {
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case rand_type_64:
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return "Full 64-bit [rte_rand()]";
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case rand_type_bounded_best_case:
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return "Bounded average best-case [rte_rand_max()]";
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case rand_type_bounded_worst_case:
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return "Bounded average worst-case [rte_rand_max()]";
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default:
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return NULL;
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}
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}
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static __rte_always_inline void
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test_rand_perf_type(enum rand_type rand_type)
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{
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uint64_t start;
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uint32_t i;
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uint64_t end;
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uint64_t sum = 0;
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uint64_t op_latency;
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start = rte_rdtsc();
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for (i = 0; i < ITERATIONS; i++) {
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switch (rand_type) {
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case rand_type_64:
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sum += rte_rand();
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break;
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case rand_type_bounded_best_case:
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sum += rte_rand_max(BEST_CASE_BOUND);
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break;
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case rand_type_bounded_worst_case:
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sum += rte_rand_max(WORST_CASE_BOUND);
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break;
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}
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}
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end = rte_rdtsc();
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/* to avoid an optimizing compiler removing the whole loop */
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vsum = sum;
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op_latency = (end - start) / ITERATIONS;
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printf("%s: %"PRId64" TSC cycles/op\n", rand_type_desc(rand_type),
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op_latency);
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}
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static int
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test_rand_perf(void)
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{
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rte_srand(42);
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printf("Pseudo-random number generation latencies:\n");
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test_rand_perf_type(rand_type_64);
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test_rand_perf_type(rand_type_bounded_best_case);
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test_rand_perf_type(rand_type_bounded_worst_case);
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return 0;
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}
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REGISTER_TEST_COMMAND(rand_perf_autotest, test_rand_perf);
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