Dmitry PotapovI have used the Cygwin version of Git on one Windows computer and noticed that git-status is sluggish. So, I have run the Process Monitor to see what is going on.
The below, you can see the result of testing on Windows and Linux on the same repository using the same version of Git. It is rather easy to compare if you notice that the following match between syscalls:
Windows Linux
QueryOpen lstat or fstat CreateFile open CloseFile close QueryDirectory getdents
I have also tested git-diff to verify that the number of system calls matches pretty well. (In fact, I got practical identical list for stat syscalls for files inside of the working directory on Windows and Linux when ran git-diff.) But something strange is going on with git-status. The beginning of the log is identical on Windows and Linux, but then I see more 'stat's in the Windows log that did not happen on Linux. In total, I see about 3 times increase of 'stat' calls, with all files being stat twice and directories (which are numerous) being stat 3 and more times (some of them as many 39 times...) It seems that every directory is stat as many times as the number of subdirectories it has plus 3.
It appears that the second 'stat' for files on Windows caused by lack of d_type in dirent. When I recompiled the Linux version with NO_D_TYPE_IN_DIRENT = YesPlease, I got the same result for files. (Still I am not sure what caused those extra stat calls for directory, maybe, it is Cygwin specific...)
The question is whether it is possible to avoid this redundant 'stat' for files on system that do not have d_type in dirent or that would require too much modification? Is it possible to use the cache where d_stat is not available provided that the entry is marked as uptodate?
==== Git on Windows (CYGWIN) =====
$ wc -l git-diff.csv git-status.csv 5186 git-diff.csv 21694 git-status.csv
$ csvtool col 5 git-diff.csv | sort | uniq -c | sort -nr | head -10
4656 QueryOpen
100 CreateFile
94 CloseFile
80 QuerySecurityFile
61 ReadFile
30 QueryInformationVolume
28 QueryAllInformationFile
26 RegOpenKey
24 RegCloseKey
20 QueryStandardInformationFile$ csvtool col 5 git-status.csv | sort | uniq -c | sort -nr | head -10
12984 QueryOpen
3086 CreateFile
2103 CloseFile
1984 QueryDirectory
988 QueryFileInternalInformationFile
132 QuerySecurityFile
100 ReadFile
77 WriteFile
55 QueryInformationVolume
53 QueryAllInformationFileSuccessful open: $ csvtool col 5,7,8 git-diff.csv | grep CreateFile,SUCCESS, | wc -l 94 $ csvtool col 5,7,8 git-status.csv | grep CreateFile,SUCCESS, | wc -l 2103
Successful open for directories: $ csvtool col 5,7,8 git-diff.csv | grep CreateFile,SUCCESS,.*Options:.*Directory | wc -l 37 $ csvtool col 5,7,8 git-status.csv | grep CreateFile,SUCCESS,.*Options:.*Directory | wc -l 1024
Not successful attempts to open $ csvtool col 5,7,8 git-diff.csv | grep CreateFile | grep -v ,SUCCESS, | wc -l 6 $ csvtool col 5,7,8 git-status.csv | grep CreateFile | grep -v ,SUCCESS, | wc -l 983
Attempts to open .gitignore $ csvtool col 5,6 git-diff.csv | grep 'CreateFile,.*\\\.gitignore' | wc -l 0 $ csvtool col 5,6 git-status.csv | grep 'CreateFile,.*\\\.gitignore' | wc -l 986
=== GIT on Linux ===
$ wc -l linux-git-* 4674 linux-git-diff.log 9807 linux-git-status.log
$ sed -e 's/(.*//' < linux-git-diff.log | sort | uniq -c | sort -rn | head -10
4237 lstat
88 mmap
56 open
50 close
50 access
48 fstat
45 mprotect
43 read
15 stat
13 munmapThe number of lstat+fstat is equal 4285 for git-diff
$ sed -e 's/(.*//' < linux-git-status.log | sort | uniq -c | sort -rn | head -10
3279 lstat
2048 open
1976 getdents
1062 close
1058 fstat
97 mmap
67 read
48 access
45 mprotect
40 writeThe number of lstat+fstat is equal 4337 for git-status.
Successful open: $ grep -c '^open(.*= [^-]' linux-* linux-git-diff.log:50 linux-git-status.log:1064
Successful open for directories: $ grep -c '^open(.*O_DIRECTORY.*= [^-]' linux-* linux-git-diff.log:1 linux-git-status.log:989
Not successful attempts to open: $ grep -c '^open(.*= -1' linux-* linux-git-diff.log:6 linux-git-status.log:984
Attempts to open .gitignore: $ grep -c '^open(.*.\.gitignore"' linux-* linux-git-diff.log:0 linux-git-status.log:987
=== Linux with NO_D_TYPE_IN_DIRENT = YesPlease ===
$ wc -l linux-git-*no-dtype.log 4674 linux-git-diff-no-dtype.log 14040 linux-git-status-no-dtype.log
$ sed -e 's/(.*//' < linux-git-diff-no-dtype.log | sort | uniq -c | sort -rn | head -10
4237 lstat
88 mmap
56 open
50 close
50 access
48 fstat
45 mprotect
43 read
15 stat
13 munmapThe number of lstat+fstat is equal 4285 for git-diff
$ sed -e 's/(.*//' < linux-git-status-no-dtype.log | sort | uniq -c | sort -rn | head -10
7512 lstat
2048 open
1976 getdents
1062 close
1058 fstat
97 mmap
67 read
48 access
45 mprotect
40 writeThe number of lstat+fstat is equal 8570 for git-status.
Successful open: $ grep -c '^open(.*= [^-]' linux-*-no-dtype.log linux-git-diff-no-dtype.log:50 linux-git-status-no-dtype.log:1064
Successful open for directories: $ grep -c '^open(.*O_DIRECTORY.*= [^-]' linux-*-no-dtype.log linux-git-diff-no-dtype.log:1 linux-git-status-no-dtype.log:989
Not successful attempts to open: $ grep -c '^open(.*= -1' linux-*-no-dtype.log linux-git-diff-no-dtype.log:6 linux-git-status-no-dtype.log:984
Attempts to open .gitignore: $ grep -c '^open(.*.\.gitignore"' linux-*-no-dtype.log linux-git-diff-no-dtype.log:0 linux-git-status-no-dtype.log:987
=======
Dmitry
