1 // SPDX-License-Identifier: GPL-2.0
3 * Cache Allocation Technology (CAT) test
5 * Copyright (C) 2018 Intel Corporation
8 * Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>,
9 * Fenghua Yu <fenghua.yu@intel.com>
14 #define RESULT_FILE_NAME "result_cat"
18 * Minimum difference in LLC misses between a test with n+1 bits CBM to the
19 * test with n bits is MIN_DIFF_PERCENT_PER_BIT * (n - 1). With e.g. 5 vs 4
20 * bits in the CBM mask, the minimum difference must be at least
21 * MIN_DIFF_PERCENT_PER_BIT * (4 - 1) = 3 percent.
23 * The relationship between number of used CBM bits and difference in LLC
24 * misses is not expected to be linear. With a small number of bits, the
25 * margin is smaller than with larger number of bits. For selftest purposes,
26 * however, linear approach is enough because ultimately only pass/fail
27 * decision has to be made and distinction between strong and stronger
28 * signal is irrelevant.
30 #define MIN_DIFF_PERCENT_PER_BIT 1UL
32 static int show_results_info(__u64 sum_llc_val, int no_of_bits,
33 unsigned long cache_span,
34 unsigned long min_diff_percent,
35 unsigned long num_of_runs, bool platform,
36 __s64 *prev_avg_llc_val)
38 __u64 avg_llc_val = 0;
42 avg_llc_val = sum_llc_val / num_of_runs;
43 if (*prev_avg_llc_val) {
44 float delta = (__s64)(avg_llc_val - *prev_avg_llc_val);
46 avg_diff = delta / *prev_avg_llc_val;
47 ret = platform && (avg_diff * 100) < (float)min_diff_percent;
49 ksft_print_msg("%s Check cache miss rate changed more than %.1f%%\n",
50 ret ? "Fail:" : "Pass:", (float)min_diff_percent);
52 ksft_print_msg("Percent diff=%.1f\n", avg_diff * 100);
54 *prev_avg_llc_val = avg_llc_val;
56 show_cache_info(no_of_bits, avg_llc_val, cache_span, true);
61 /* Remove the highest bit from CBM */
62 static unsigned long next_mask(unsigned long current_mask)
64 return current_mask & (current_mask >> 1);
67 static int check_results(struct resctrl_val_param *param, const char *cache_type,
68 unsigned long cache_total_size, unsigned long full_cache_mask,
69 unsigned long current_mask)
71 char *token_array[8], temp[512];
72 __u64 sum_llc_perf_miss = 0;
73 __s64 prev_avg_llc_val = 0;
74 unsigned long alloc_size;
80 ksft_print_msg("Checking for pass/fail\n");
81 fp = fopen(param->filename, "r");
83 ksft_perror("Cannot open file");
88 while (fgets(temp, sizeof(temp), fp)) {
89 char *token = strtok(temp, ":\t");
94 token_array[fields++] = token;
95 token = strtok(NULL, ":\t");
98 sum_llc_perf_miss += strtoull(token_array[3], NULL, 0);
101 if (runs < NUM_OF_RUNS)
105 ksft_print_msg("Unexpected empty cache mask\n");
109 alloc_size = cache_portion_size(cache_total_size, current_mask, full_cache_mask);
111 bits = count_bits(current_mask);
113 ret = show_results_info(sum_llc_perf_miss, bits,
115 MIN_DIFF_PERCENT_PER_BIT * (bits - 1),
116 runs, get_vendor() == ARCH_INTEL,
122 sum_llc_perf_miss = 0;
123 current_mask = next_mask(current_mask);
131 void cat_test_cleanup(void)
133 remove(RESULT_FILE_NAME);
137 * cat_test - Execute CAT benchmark and measure cache misses
138 * @test: Test information structure
139 * @uparams: User supplied parameters
140 * @param: Parameters passed to cat_test()
141 * @span: Buffer size for the benchmark
142 * @current_mask Start mask for the first iteration
144 * Run CAT selftest by varying the allocated cache portion and comparing the
145 * impact on cache misses (the result analysis is done in check_results()
146 * and show_results_info(), not in this function).
148 * One bit is removed from the CAT allocation bit mask (in current_mask) for
149 * each subsequent test which keeps reducing the size of the allocated cache
150 * portion. A single test flushes the buffer, reads it to warm up the cache,
151 * and reads the buffer again. The cache misses are measured during the last
154 * Return: 0 when the test was run, < 0 on error.
156 static int cat_test(const struct resctrl_test *test,
157 const struct user_params *uparams,
158 struct resctrl_val_param *param,
159 size_t span, unsigned long current_mask)
161 char *resctrl_val = param->resctrl_val;
162 struct perf_event_read pe_read;
163 struct perf_event_attr pea;
164 cpu_set_t old_affinity;
170 if (strcmp(param->filename, "") == 0)
171 sprintf(param->filename, "stdio");
175 /* Taskset benchmark to specified cpu */
176 ret = taskset_benchmark(bm_pid, uparams->cpu, &old_affinity);
180 /* Write benchmark to specified con_mon grp, mon_grp in resctrl FS*/
181 ret = write_bm_pid_to_resctrl(bm_pid, param->ctrlgrp, param->mongrp,
186 perf_event_attr_initialize(&pea, PERF_COUNT_HW_CACHE_MISSES);
187 perf_event_initialize_read_format(&pe_read);
188 pe_fd = perf_open(&pea, bm_pid, uparams->cpu);
194 buf = alloc_buffer(span, 1);
200 while (current_mask) {
201 snprintf(schemata, sizeof(schemata), "%lx", param->mask & ~current_mask);
202 ret = write_schemata("", schemata, uparams->cpu, test->resource);
205 snprintf(schemata, sizeof(schemata), "%lx", current_mask);
206 ret = write_schemata(param->ctrlgrp, schemata, uparams->cpu, test->resource);
210 for (i = 0; i < NUM_OF_RUNS; i++) {
211 mem_flush(buf, span);
212 fill_cache_read(buf, span, true);
214 ret = perf_event_reset_enable(pe_fd);
218 fill_cache_read(buf, span, true);
220 ret = perf_event_measure(pe_fd, &pe_read, param->filename, bm_pid);
224 current_mask = next_mask(current_mask);
232 taskset_restore(bm_pid, &old_affinity);
237 static int cat_run_test(const struct resctrl_test *test, const struct user_params *uparams)
239 unsigned long long_mask, start_mask, full_cache_mask;
240 unsigned long cache_total_size = 0;
241 int n = uparams->bits;
247 ret = get_full_cbm(test->resource, &full_cache_mask);
250 /* Get the largest contiguous exclusive portion of the cache */
251 ret = get_mask_no_shareable(test->resource, &long_mask);
255 /* Get L3/L2 cache size */
256 ret = get_cache_size(uparams->cpu, test->resource, &cache_total_size);
259 ksft_print_msg("Cache size :%lu\n", cache_total_size);
261 count_of_bits = count_contiguous_bits(long_mask, &start);
264 n = count_of_bits / 2;
266 if (n > count_of_bits - 1) {
267 ksft_print_msg("Invalid input value for no_of_bits n!\n");
268 ksft_print_msg("Please enter value in range 1 to %d\n",
272 start_mask = create_bit_mask(start, n);
274 struct resctrl_val_param param = {
275 .resctrl_val = CAT_STR,
277 .filename = RESULT_FILE_NAME,
280 param.mask = long_mask;
281 span = cache_portion_size(cache_total_size, start_mask, full_cache_mask);
283 remove(param.filename);
285 ret = cat_test(test, uparams, ¶m, span, start_mask);
289 ret = check_results(¶m, test->resource,
290 cache_total_size, full_cache_mask, start_mask);
297 static int noncont_cat_run_test(const struct resctrl_test *test,
298 const struct user_params *uparams)
300 unsigned long full_cache_mask, cont_mask, noncont_mask;
301 unsigned int eax, ebx, ecx, edx, sparse_masks;
305 /* Check to compare sparse_masks content to CPUID output. */
306 ret = resource_info_unsigned_get(test->resource, "sparse_masks", &sparse_masks);
310 if (!strcmp(test->resource, "L3"))
311 __cpuid_count(0x10, 1, eax, ebx, ecx, edx);
312 else if (!strcmp(test->resource, "L2"))
313 __cpuid_count(0x10, 2, eax, ebx, ecx, edx);
317 if (sparse_masks != ((ecx >> 3) & 1)) {
318 ksft_print_msg("CPUID output doesn't match 'sparse_masks' file content!\n");
322 /* Write checks initialization. */
323 ret = get_full_cbm(test->resource, &full_cache_mask);
326 bit_center = count_bits(full_cache_mask) / 2;
329 * The bit_center needs to be at least 3 to properly calculate the CBM
330 * hole in the noncont_mask. If it's smaller return an error since the
331 * cache mask is too short and that shouldn't happen.
335 cont_mask = full_cache_mask >> bit_center;
337 /* Contiguous mask write check. */
338 snprintf(schemata, sizeof(schemata), "%lx", cont_mask);
339 ret = write_schemata("", schemata, uparams->cpu, test->resource);
341 ksft_print_msg("Write of contiguous CBM failed\n");
346 * Non-contiguous mask write check. CBM has a 0xf hole approximately in the middle.
347 * Output is compared with support information to catch any edge case errors.
349 noncont_mask = ~(0xfUL << (bit_center - 2)) & full_cache_mask;
350 snprintf(schemata, sizeof(schemata), "%lx", noncont_mask);
351 ret = write_schemata("", schemata, uparams->cpu, test->resource);
352 if (ret && sparse_masks)
353 ksft_print_msg("Non-contiguous CBMs supported but write of non-contiguous CBM failed\n");
354 else if (ret && !sparse_masks)
355 ksft_print_msg("Non-contiguous CBMs not supported and write of non-contiguous CBM failed as expected\n");
356 else if (!ret && !sparse_masks)
357 ksft_print_msg("Non-contiguous CBMs not supported but write of non-contiguous CBM succeeded\n");
359 return !ret == !sparse_masks;
362 static bool noncont_cat_feature_check(const struct resctrl_test *test)
364 if (!resctrl_resource_exists(test->resource))
367 return resource_info_file_exists(test->resource, "sparse_masks");
370 struct resctrl_test l3_cat_test = {
374 .feature_check = test_resource_feature_check,
375 .run_test = cat_run_test,
378 struct resctrl_test l3_noncont_cat_test = {
379 .name = "L3_NONCONT_CAT",
382 .feature_check = noncont_cat_feature_check,
383 .run_test = noncont_cat_run_test,
386 struct resctrl_test l2_noncont_cat_test = {
387 .name = "L2_NONCONT_CAT",
390 .feature_check = noncont_cat_feature_check,
391 .run_test = noncont_cat_run_test,