MantisBT - CMake
2. there are know approaches to tackle this problem, such as recent improvements in git (http://kerneltrap.org/index.php?q=mailarchive/git/2008/9/27/3427614 [^])
3. CMake profiling during cmake_depends option execution shows that indeed calls to POSIX access function is the main bottleneck.
4. Simple benchmarking (approx. 700 files in a single directory, 80000 random executions of access) shows that it takes around 36 secs on cygwin/ntfs system regardless of the full/relative path being passed as access' argument.
5. the main source of calls to POSIX access in CMake is a function checking for file existence: SystemTools::FileExists
6. since on Cygwin file can be read even if a user has no reading rights replacing access with GetFileAttributesExA can be made to check for file existence. This requires conversion of cygwin paths to native Win32 form using a cygwin_conv_to_win32_path utility provided with the cygwin dll
7. this change alone brings drastic improvements in CMake performance during cmake_depends execution, however, the next bottleneck becomes the cygwin_conv_to_win32_path function. Fortunately we can cache path translations what moves this problem aside.
8. the attached patches for files cmake-2.6.3/Source/kwsys/SystemTools.cxx and cmake-2.6.3/Source/kwsys/SystemTools.hxx.in attempt to introduce basic changes to the way CMake checks for file existence. For one of the targets we have in our build system (ca. 130 .c files, 78,000 executions of access to check existnce of some of almost 700 headers) this cahnge has reduced cmake_depends timing from 36 secs to ca. 6 secs !!
patches.zip (2,075) 2009-03-31 14:42https://public.kitware.com/Bug/file/2148/patches.zip