Cygwin Filesystem Performance degradation 1.7.5 vs 1.7.7, and methods for improving performance

[Yoni Londner]

Hi,

I checked a little bit the performance of bash loading.
I run 'bash -l -c "echo "', and got around 4 seconds!

I checked (via strace) out and found it performs a lot of redundant file
read on symlinks (75 symlinks read, where only 10 are needed).

I added a debug_print in symlink_info::check_sysfile (just to see how
many times we call it) and got the following results:
5 times:
symlink_info::check: 0x0 = NtCreateFile (\??\C:\cygwin\bin\autoconf)
5576 symlink_info::check_sysfile: res 34

12 times:
symlink_info::check: 0x0 = NtCreateFile (\??\C:\cygwin\bin\automake)
symlink_info::check_sysfile: res 26

6 times:
symlink_info::check: 0x0 = NtCreateFile (\??\C:\cygwin\bin\awk)
symlink_info::check_sysfile: res 8

and so on...
All in the same process!

symlink caching solves this, and reduces it from 75 -> 10 (similar to
fs_info_cache).

Yoni.