| /* Benchmark utility functions. |
| Copyright (C) 2015-2018 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 |
| <http://www.gnu.org/licenses/>. */ |
| |
| |
| static volatile unsigned int dontoptimize = 0; |
| |
| void |
| bench_start (void) |
| { |
| /* This loop should cause CPU to switch to maximal freqency. |
| This makes subsequent measurement more accurate. We need a side effect |
| to prevent the loop being deleted by compiler. |
| This should be enough to cause CPU to speed up and it is simpler than |
| running loop for constant time. This is used when user does not have root |
| access to set a constant freqency. */ |
| |
| for (int k = 0; k < START_ITER; k++) |
| dontoptimize += 23 * dontoptimize + 2; |
| } |