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authorGarima Singh <garima.singh@microsoft.com>2019-09-04 17:36:39 (GMT)
committerJohannes Schindelin <johannes.schindelin@gmx.de>2019-12-05 14:36:40 (GMT)
commita62f9d1ace8c6556cbc1bb7df69eff0a0bb9e774 (patch)
treef8bf257b2070986f147000a8638fd522cf070d36 /t/helper/test-path-utils.c
parent525e7fba7854c23ee3530d0bf88d75f106f14c95 (diff)
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test-path-utils: offer to run a protectNTFS/protectHFS benchmark
In preparation to flipping the default on `core.protectNTFS`, let's have some way to measure the speed impact of this config setting reliably (and for comparison, the `core.protectHFS` config setting). For now, this is a manual performance benchmark: ./t/helper/test-path-utils protect_ntfs_hfs [arguments...] where the arguments are an optional number of file names to test with, optionally followed by minimum and maximum length of the random file names. The default values are one million, 3 and 20, respectively. Just like `sqrti()` in `bisect.c`, we introduce a very simple function to approximation the square root of a given value, in order to avoid having to introduce the first user of `<math.h>` in Git's source code. Note: this is _not_ implemented as a Unix shell script in t/perf/ because we really care about _very_ precise timings here, and Unix shell scripts are simply unsuited for precise and consistent benchmarking. Signed-off-by: Garima Singh <garima.singh@microsoft.com> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Diffstat (limited to 't/helper/test-path-utils.c')
-rw-r--r--t/helper/test-path-utils.c96
1 files changed, 96 insertions, 0 deletions
diff --git a/t/helper/test-path-utils.c b/t/helper/test-path-utils.c
index 9484655..16d8e68 100644
--- a/t/helper/test-path-utils.c
+++ b/t/helper/test-path-utils.c
@@ -176,6 +176,99 @@ static int is_dotgitmodules(const char *path)
return is_hfs_dotgitmodules(path) || is_ntfs_dotgitmodules(path);
}
+/*
+ * A very simple, reproducible pseudo-random generator. Copied from
+ * `test-genrandom.c`.
+ */
+static uint64_t my_random_value = 1234;
+
+static uint64_t my_random(void)
+{
+ my_random_value = my_random_value * 1103515245 + 12345;
+ return my_random_value;
+}
+
+/*
+ * A fast approximation of the square root, without requiring math.h.
+ *
+ * It uses Newton's method to approximate the solution of 0 = x^2 - value.
+ */
+static double my_sqrt(double value)
+{
+ const double epsilon = 1e-6;
+ double x = value;
+
+ if (value == 0)
+ return 0;
+
+ for (;;) {
+ double delta = (value / x - x) / 2;
+ if (delta < epsilon && delta > -epsilon)
+ return x + delta;
+ x += delta;
+ }
+}
+
+static int protect_ntfs_hfs_benchmark(int argc, const char **argv)
+{
+ size_t i, j, nr, min_len = 3, max_len = 20;
+ char **names;
+ int repetitions = 15, file_mode = 0100644;
+ uint64_t begin, end;
+ double m[3][2], v[3][2];
+ uint64_t cumul;
+ double cumul2;
+
+ if (argc > 1 && !strcmp(argv[1], "--with-symlink-mode")) {
+ file_mode = 0120000;
+ argc--;
+ argv++;
+ }
+
+ nr = argc > 1 ? strtoul(argv[1], NULL, 0) : 1000000;
+ ALLOC_ARRAY(names, nr);
+
+ if (argc > 2) {
+ min_len = strtoul(argv[2], NULL, 0);
+ if (argc > 3)
+ max_len = strtoul(argv[3], NULL, 0);
+ if (min_len > max_len)
+ die("min_len > max_len");
+ }
+
+ for (i = 0; i < nr; i++) {
+ size_t len = min_len + (my_random() % (max_len + 1 - min_len));
+
+ names[i] = xmallocz(len);
+ while (len > 0)
+ names[i][--len] = (char)(' ' + (my_random() % ('\x7f' - ' ')));
+ }
+
+ for (protect_ntfs = 0; protect_ntfs < 2; protect_ntfs++)
+ for (protect_hfs = 0; protect_hfs < 2; protect_hfs++) {
+ cumul = 0;
+ cumul2 = 0;
+ for (i = 0; i < repetitions; i++) {
+ begin = getnanotime();
+ for (j = 0; j < nr; j++)
+ verify_path(names[j], file_mode);
+ end = getnanotime();
+ printf("protect_ntfs = %d, protect_hfs = %d: %lfms\n", protect_ntfs, protect_hfs, (end-begin) / (double)1e6);
+ cumul += end - begin;
+ cumul2 += (end - begin) * (end - begin);
+ }
+ m[protect_ntfs][protect_hfs] = cumul / (double)repetitions;
+ v[protect_ntfs][protect_hfs] = my_sqrt(cumul2 / (double)repetitions - m[protect_ntfs][protect_hfs] * m[protect_ntfs][protect_hfs]);
+ printf("mean: %lfms, stddev: %lfms\n", m[protect_ntfs][protect_hfs] / (double)1e6, v[protect_ntfs][protect_hfs] / (double)1e6);
+ }
+
+ for (protect_ntfs = 0; protect_ntfs < 2; protect_ntfs++)
+ for (protect_hfs = 0; protect_hfs < 2; protect_hfs++)
+ printf("ntfs=%d/hfs=%d: %lf%% slower\n", protect_ntfs, protect_hfs, (m[protect_ntfs][protect_hfs] - m[0][0]) * 100 / m[0][0]);
+
+ return 0;
+}
+
int cmd_main(int argc, const char **argv)
{
if (argc == 3 && !strcmp(argv[1], "normalize_path_copy")) {
@@ -290,6 +383,9 @@ int cmd_main(int argc, const char **argv)
return !!res;
}
+ if (argc > 1 && !strcmp(argv[1], "protect_ntfs_hfs"))
+ return !!protect_ntfs_hfs_benchmark(argc - 1, argv + 1);
+
fprintf(stderr, "%s: unknown function name: %s\n", argv[0],
argv[1] ? argv[1] : "(there was none)");
return 1;