199fa6015d
zipf is a power law probability distribution. When applied to performance testing of block devices, it will select blocks over the full range of LBAs, but will more frequently select lower-numbered LBAs. The theta parameter governs the distribution - higher values of theta will concentrate the distribution on a smaller number of LBAs. Note that fio supports zipf, so adding it to SPDK will enable our perf tools (bdevperf, nvme-perf) to provide similar functionality. Signed-off-by: Jim Harris <james.r.harris@intel.com> Change-Id: I7df129c9d61996a2070188c6cd9f1fde631ac208 Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/7779 Tested-by: SPDK CI Jenkins <sys_sgci@intel.com> Community-CI: Broadcom CI Community-CI: Mellanox Build Bot Reviewed-by: Ben Walker <benjamin.walker@intel.com> Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
140 lines
3.9 KiB
C
140 lines
3.9 KiB
C
/*-
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* BSD LICENSE
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*
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* Copyright(c) Intel Corporation. All rights reserved.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* * Neither the name of Intel Corporation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "spdk/stdinc.h"
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#include "spdk/util.h"
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#include "spdk/zipf.h"
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struct spdk_zipf {
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uint64_t range;
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double alpha;
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double eta;
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double theta;
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double zetan;
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double val1_limit;
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uint32_t seed;
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};
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static double
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zeta_increment(uint64_t n, double theta)
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{
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return pow((double) 1.0 / (n + 1), theta);
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}
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static double
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zeta(uint64_t range, double theta)
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{
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double zetan = 0;
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double inc1, inc2;
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uint64_t i, calc, count;
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const uint32_t ZIPF_MAX_ZETA_CALC = 10 * 1000 * 1000;
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const uint32_t ZIPF_ZETA_ESTIMATE = 1 * 1000 * 1000;
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/* Cumulate zeta discretely for the first ZIPF_MAX_ZETA_CALC
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* entries in the range.
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*/
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calc = spdk_min(ZIPF_MAX_ZETA_CALC, range);
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for (i = 0; i < calc; i++) {
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zetan += zeta_increment(i, theta);
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}
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/* For the remaining values in the range, increment zetan
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* with an approximation for every ZIPF_ZETA_ESTIMATE
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* entries. We will take an average of the increment
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* for (i) and (i + ZIPF_ZETA_ESTIMATE), and then multiply
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* that by ZIPF_ZETA_ESTIMATE.
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*
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* Of course, we'll cap ZIPF_ZETA_ESTIMATE to something
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* smaller if necessary at the end of the range.
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*/
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while (i < range) {
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count = spdk_min(ZIPF_ZETA_ESTIMATE, range - i);
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inc1 = zeta_increment(i, theta);
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inc2 = zeta_increment(i + count, theta);
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zetan += (inc1 + inc2) * count / 2;
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i += count;
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}
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return zetan;
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}
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struct spdk_zipf *
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spdk_zipf_create(uint64_t range, double theta, uint32_t seed)
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{
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struct spdk_zipf *zipf;
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zipf = calloc(1, sizeof(*zipf));
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if (zipf == NULL) {
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return NULL;
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}
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zipf->range = range;
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zipf->seed = seed;
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zipf->theta = theta;
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zipf->alpha = 1.0 / (1.0 - zipf->theta);
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zipf->zetan = zeta(range, theta);
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zipf->eta = (1.0 - pow(2.0 / zipf->range, 1.0 - zipf->theta)) /
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(1.0 - zeta(2, theta) / zipf->zetan);
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zipf->val1_limit = 1.0 + pow(0.5, zipf->theta);
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return zipf;
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}
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void
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spdk_zipf_free(struct spdk_zipf **zipfp)
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{
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assert(zipfp != NULL);
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free(*zipfp);
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*zipfp = NULL;
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}
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uint64_t
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spdk_zipf_generate(struct spdk_zipf *zipf)
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{
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double randu, randz;
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uint64_t val;
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randu = (double)rand_r(&zipf->seed) / RAND_MAX;
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randz = randu * zipf->zetan;
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if (randz < 1.0) {
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return 0;
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} else if (randz < zipf->val1_limit) {
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return 1;
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} else {
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val = zipf->range * pow(zipf->eta * (randu - 1.0) + 1.0, zipf->alpha);
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return val % zipf->range;
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}
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}
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