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([2804:431:c7ca:c6c7:f05e:9652:ab99:7fa2]) by smtp.gmail.com with ESMTPSA id p6sm3826999vko.16.2021.10.15.05.52.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 15 Oct 2021 05:52:36 -0700 (PDT) Subject: Re: [PATCH v3 1/7] benchtests: Add bench-qsort To: Noah Goldstein References: <20210903171144.952737-1-adhemerval.zanella@linaro.org> <20210903171144.952737-2-adhemerval.zanella@linaro.org> Message-ID: Date: Fri, 15 Oct 2021 09:52:34 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Adhemerval Zanella via Libc-alpha Reply-To: Adhemerval Zanella Cc: GNU C Library Errors-To: libc-alpha-bounces+e=80x24.org@sourceware.org Sender: "Libc-alpha" On 13/10/2021 00:19, Noah Goldstein wrote: > On Fri, Sep 3, 2021 at 1:13 PM Adhemerval Zanella via Libc-alpha > wrote: >> >> This patch adds a qsort benchmark. I tried to model the benchmark >> taking in consideration the possible input variation in both internal >> element size, element numbers, and internal state for 1. real word cases >> and 2. possible scenarios based on hardware characteristics. >> >> For 1. I tracked qsort usage (using a simple preload library to dump its >> usage and a script to pos-process it) on both GCC bootstrap and Firefox. >> GCC 8 bootstrap build shows 51786641 call to qsort with the following >> characterics: >> >> Key: number of elements: >> key=2 : 39.74 >> key=3 : 19.23 >> key=4 : 9.77 >> key=1 : 8.44 >> key=0 : 6.60 >> key=5 : 4.40 >> key=7 : 2.37 >> key=6 : 2.25 >> key=9 : 1.48 >> key=8 : 0.97 >> >> Key: element size in bytes: >> key=8 : 91.74 >> key=32 : 3.62 >> key=4 : 2.42 >> key=40 : 1.20 >> key=16 : 0.67 >> key=24 : 0.30 >> key=48 : 0.05 >> key=56 : 0.00 >> key=1 : 0.00 >> >> Key: total size (number of elements * element size): >> key=16 : 35.98 >> key=24 : 18.67 >> key=32 : 9.79 >> key=8 : 8.28 >> key=0 : 6.60 >> key=40 : 4.21 >> key=64 : 3.15 >> key=48 : 2.24 >> key=56 : 2.15 >> key=80 : 1.45 >> >> So for GCC: >> >> - 80% of total qsort usage are done with 10 elements of less. >> - All usages are done element size of maximum of 56 bytes. >> - 90% of calls are done with array of maximum size of 80 bytes or >> less. >> >> (GCC on recent version now uses a internal qsort implementation instead >> of the libc one). >> >> The Firefox usage was done with 2 hours of usage, with first 10 minutes >> activelly openning and closing different types of sites. It resulted in >> 21042 calls with following characteristics: >> >> Key: number of elements: >> key=7 : 24.40 >> key=1 : 10.44 >> key=3 : 6.33 >> key=4 : 5.81 >> key=2 : 5.46 >> key=6 : 4.80 >> key=17 : 4.54 >> key=0 : 3.07 >> key=5 : 3.05 >> key=9 : 2.51 >> key=12 : 2.06 >> >> Key: element size in bytes: >> key=8 : 94.49 >> key=28 : 4.40 >> key=2 : 0.70 >> key=16 : 0.19 >> key=36 : 0.07 >> key=12 : 0.07 >> key=40 : 0.07 >> key=24 : 0.03 >> >> Key: total size (number of elements * element size): >> key=56 : 24.20 >> key=8 : 10.27 >> key=24 : 6.36 >> key=32 : 5.86 >> key=16 : 5.46 >> key=48 : 4.80 >> key=476 : 3.75 >> key=0 : 3.07 >> key=40 : 3.05 >> key=72 : 2.50 >> >> So for Firefox: >> >> - 72% of total qsort usage are done with 18 elements of less. >> - All usages are done element size of maximum of 40 bytes. >> - 70% of calls are done with array of maximum size of 476 bytes or >> less. >> >> For 2. I used the idea of a machine with 3 levels of cache with sizes >> L1 32kb, L2 256kb, and L3 4096Kb. >> >> It resulted in a benchmark with following traits: >> >> * It checks four types of input arrays: sorted, mostly sorted, random, >> repeated, and bitonic: >> >> - 'sorted': the array is already sorted. >> - 'mostly sorted': the array will have a certain number of random >> position with random values (current ratio used is 20%). >> - 'random' the array will contain random elements. >> - 'repeated' the array will have random elements with a certain >> number (current ratio is 20%) of a repeated element distributed >> randomly. >> - 'bitonic': elements will be strictly increasing to up middle of the >> array then strictly decreasing. This is to trigger the >> pattern-defeting input for the median of 3 pivot selection used >> in quicksort implementation. >> >> * Three elements sizes are checked: uint32_t, uint64_t, and an >> element with 32 bytes (but using the uint32_t comparison checks). >> These element sizes are used to 1. to avoid include the comparison >> function itself and/or memory copy in sort benchmark itself, and 2. >> because key of size_t are the most used for both GCC and Firefox. >> >> * Five different element numbers: 64 (which cover mostly of used >> elementsizes for both GCC and Firefox), 4096/8192 (which cover 32 KB >> of L1 for 32 and 64 bits), 32768/65536 (L2 with 256 KB), and >> 24288/1048576 (L3 with 4 MB). The sizes are configurable by >> --nelem option. >> >> Checked on x86_64-linux-gnu >> --- >> benchtests/Makefile | 2 +- >> benchtests/bench-qsort.c | 195 +++++++++++++++++++++++++++++++++++++++ >> 2 files changed, 196 insertions(+), 1 deletion(-) >> create mode 100644 benchtests/bench-qsort.c >> >> diff --git a/benchtests/Makefile b/benchtests/Makefile >> index 1530939a8c..781cbca8af 100644 >> --- a/benchtests/Makefile >> +++ b/benchtests/Makefile >> @@ -76,7 +76,7 @@ LOCALES := en_US.UTF-8 tr_TR.UTF-8 cs_CZ.UTF-8 fa_IR.UTF-8 fr_FR.UTF-8 \ >> include ../gen-locales.mk >> endif >> >> -stdlib-benchset := strtod >> +stdlib-benchset := strtod qsort >> >> stdio-common-benchset := sprintf >> >> diff --git a/benchtests/bench-qsort.c b/benchtests/bench-qsort.c >> new file mode 100644 >> index 0000000000..905aa6d7b6 >> --- /dev/null >> +++ b/benchtests/bench-qsort.c >> @@ -0,0 +1,195 @@ >> +/* Measure qsort function. >> + Copyright (C) 2018 Free Software Foundation, Inc. >> + This file is part of the GNU C Library. >> + >> + The GNU C Library is free software; you can redistribute it and/or >> + modify it under the terms of the GNU Lesser General Public >> + License as published by the Free Software Foundation; either >> + version 2.1 of the License, or (at your option) any later version. >> + >> + The GNU C Library is distributed in the hope that it will be useful, >> + but WITHOUT ANY WARRANTY; without even the implied warranty of >> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU >> + Lesser General Public License for more details. >> + >> + You should have received a copy of the GNU Lesser General Public >> + License along with the GNU C Library; if not, see >> + . */ >> + >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> + >> +#include >> + >> +/* Number of elements of determined type to be measured. */ >> +static const size_t default_nelems[] = >> +{ >> + 256/sizeof(size_t), /* 64/128 which covers mostly used element number >> + on GCC build. */ >> + 32768/sizeof(size_t), /* 4096/8192 to fit on a L1 with 32 KB. */ >> + 262144/sizeof(size_t), /* 32768/65536 to fit on a L2 with 256 KB. */ >> + 4194304/sizeof(size_t), /* 524288/1048576 to fix on a L3 with 4 MB. */ >> +}; >> + >> +#define OPT_NELEM 10000 >> +#define OPT_SEED 10001 >> +#define CMDLINE_OPTIONS \ >> + { "nelem", required_argument, NULL, OPT_NELEM }, \ >> + { "seed", required_argument, NULL, OPT_SEED }, >> + >> +static const size_t max_nelem = 16; >> +static size_t *elems = NULL; >> +static size_t nelem = 0; >> +static uint64_t seed = 0; >> +static bool seed_set = false; >> + >> +static void >> +cmdline_process_function (int c) >> +{ >> + switch (c) >> + { >> + /* Handle the --nelem option to run different sizes than DEFAULT_ELEM. >> + The elements sizes as passed with a ':' as the delimiter, for >> + instance --nelem 32:128:1024 will ran 32, 128, and 1024 elements. */ >> + case OPT_NELEM: >> + { >> + elems = xmalloc (max_nelem * sizeof (size_t)); >> + nelem = 0; >> + >> + char *saveptr; >> + char *token; >> + token = strtok_r (optarg, ":", &saveptr); >> + if (token == NULL) >> + { >> + printf ("error: invalid --nelem value\n"); >> + exit (EXIT_FAILURE); >> + } >> + do >> + { >> + if (nelem == max_nelem) >> + { >> + printf ("error: invalid --nelem value (max elem)\n"); >> + exit (EXIT_FAILURE); >> + } >> + elems[nelem++] = atol (token); >> + token = strtok_r (saveptr, ":", &saveptr); >> + } while (token != NULL); >> + } >> + break; >> + >> + /* handle the --seed option to use a different seed than a random one. >> + The SEED used should be a uint64_t number. */ >> + case OPT_SEED: >> + { >> + uint64_t value = strtoull (optarg, NULL, 0); >> + if (errno == ERANGE || value > UINT64_MAX) >> + { >> + printf ("error: seed should be a value in range of " >> + "[0, UINT64_MAX]\n"); >> + exit (EXIT_FAILURE); >> + } >> + seed = value; >> + seed_set = true; >> + } >> + } >> +} >> + >> +#define CMDLINE_PROCESS cmdline_process_function >> + >> +static int >> +do_test (void) >> +{ >> + random_init (); >> + >> + >> + json_ctx_t json_ctx; >> + >> + json_init (&json_ctx, 0, stdout); >> + >> + json_document_begin (&json_ctx); >> + json_attr_string (&json_ctx, "timing_type", TIMING_TYPE); >> + >> + json_attr_object_begin (&json_ctx, "functions"); >> + json_attr_object_begin (&json_ctx, "qsort"); >> + json_attr_uint (&json_ctx, "seed", seed); >> + >> + json_array_begin (&json_ctx, "results"); >> + >> + const size_t *welem = elems == NULL ? default_nelems : elems; >> + const size_t wnelem = elems == NULL ? array_length (default_nelems) : nelem; >> + >> + struct test_t >> + { >> + size_t type_size; >> + cmpfunc_t cmpfunc; >> + }; >> + static const struct test_t tests[] = >> + { >> + { sizeof (uint32_t), uint32_t_cmp }, >> + { sizeof (uint64_t), uint64_t_cmp }, >> + /* Test swap with large elements. */ >> + { 32, uint32_t_cmp }, >> + }; >> + >> + const size_t inner_loop_iters = 16; >> + for (const struct test_t *test = tests; test < array_end (tests); ++test) >> + { >> + for (const struct array_t *arraytype = arraytypes; >> + arraytype < array_end (arraytypes); >> + ++arraytype) >> + { >> + for (int k = 0; k < wnelem; k++) >> + { >> + json_element_object_begin (&json_ctx); >> + >> + size_t arraysize = welem[k] * test->type_size; >> + >> + json_attr_uint (&json_ctx, "nmemb", welem[k]); >> + json_attr_uint (&json_ctx, "type_size", test->type_size); >> + json_attr_string (&json_ctx, "property", arraytype->name); >> + >> + void *base = create_array (welem[k], test->type_size, >> + arraytype->type); >> + void *work = xmalloc (arraysize); >> + >> + timing_t total = 0; >> + >> + for (int n = 0; n < inner_loop_iters; n++) >> + { >> + memcpy (work, base, arraysize); >> + >> + timing_t start, end, diff; >> + TIMING_NOW (start); >> + qsort (work, welem[k], test->type_size, test->cmpfunc); >> + TIMING_NOW (end); >> + >> + TIMING_DIFF (diff, start, end); >> + TIMING_ACCUM (total, diff); >> + } >> + > To avoid overhead from timing. Maybe you could allocate / initialize > multiple buffers to test a given sort on. Then instead of having to > re-memcpy / time you just loop through the N initialized buffers > with one timing call. For the smaller sorts this may help decrease > the timing overhead. I think this make sense, although it would require more memory. I changed to: --- for (const struct test_t *test = tests; test < array_end (tests); ++test) { for (size_t at = 0; at < array_length (arraytypes); at++) { for (int ne = 0; ne < wnelem; ne++) { void *inputs[INNER_LOOP_ITERS]; for (int i = 0; i < INNER_LOOP_ITERS; i++) inputs[i] = create_array (welem[ne], test->type_size, arraytypes[at].type); timing_t start, end, diff; TIMING_NOW (start); for (int i = 0; i < INNER_LOOP_ITERS; i++) qsort (inputs[i], welem[ne], test->type_size, test->cmpfunc); TIMING_NOW (end); TIMING_DIFF (diff, start, end); json_element_object_begin (&json_ctx); json_attr_uint (&json_ctx, "nmemb", welem[ne]); json_attr_uint (&json_ctx, "type_size", test->type_size); json_attr_string (&json_ctx, "property", arraytypes[at].name); uint64_t timing = (double) diff / (double) INNER_LOOP_ITERS; json_attr_uint (&json_ctx, "timings", timing); json_element_object_end (&json_ctx); for (int i = 0; i < INNER_LOOP_ITERS; i++) free (inputs[i]); } } } ---