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cb2f668d | 1 | /* Benchmark utility functions. |
6d7e8eda | 2 | Copyright (C) 2015-2023 Free Software Foundation, Inc. |
cb2f668d WD |
3 | This file is part of the GNU C Library. |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library; if not, see | |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
cb2f668d WD |
18 | |
19 | ||
20 | static volatile unsigned int dontoptimize = 0; | |
21 | ||
22 | void | |
23 | bench_start (void) | |
24 | { | |
25 | /* This loop should cause CPU to switch to maximal freqency. | |
26 | This makes subsequent measurement more accurate. We need a side effect | |
27 | to prevent the loop being deleted by compiler. | |
28 | This should be enough to cause CPU to speed up and it is simpler than | |
29 | running loop for constant time. This is used when user does not have root | |
30 | access to set a constant freqency. */ | |
31 | ||
32 | for (int k = 0; k < START_ITER; k++) | |
33 | dontoptimize += 23 * dontoptimize + 2; | |
34 | } |