Re: [Gnu-arch-users] Re: [PATCH] arch speedups on big trees

[Aaron Bentley]

Tom Lord wrote:

>    > From: Aaron Bentley <address@hidden>
>
> There's a function in `src/tla/libarch/make-change.c' called
> `emit_file_or_symlink_patches' that creates the file for diff output
> before figuring out if there will _be_ any diff output.  It deletes
> the file if diff invocation exits with status 0.  At the same time,
> the only way that diff is ever invoked, from `arch_invoke_diff',
> doesn't bother to actually invoke diff unless it is certain that there
> _will_ be output (this was a big performance improvement a while
> back).  Simply deferring the creation of the file until it is certain
> that diff will actually run will do the trick.  It's a simple
> refactoring.
I've applied my own version of this idea to the 1.2 branch
address@hidden/tlasrc--local--1.2--patch-9

You can snag it at
http://sourcecontrol.net/~abentley/archives/tlasrc/ (thanks James!)

I also added a test for whether files are hard links of one another.

I benched it with three runs of "time tla changes" on copies of 
tlasrc--local--1.2--patch-8 that had no changes.

On normal trees, it was 1.19x faster.  On hard-linked trees, it was 
1.27x faster.  System time was 2.3x faster.  Details are attached.

On a clean, hard-linked, NFS tree, it should be much faster than vanilla 
tla, since it will only do 2 lstats per file in the tree, and it won't 
create any tmp files unless diff is required.  Further refinements could 
remove that rename by saving it under the correct name to start with.

Aaron

Run                     Real    User    Sys
Patch-8 1               4.54    3.73    0.78
Patch-8 2               4.37    3.61    0.76
Patch-8 3               4.4     3.48    0.88
                        4.44    3.61    0.81
                        100.00% 100.00% 100.00%
                        
Patch-9 nolink 1        3.72    3.32    0.4
Patch-9 nolink 2        3.73    3.39    0.33
Patch-9 nolink 3        3.72    3.39    0.32
                        3.72    3.37    0.35
                        119.24% 107.13% 230.48%
                        
Patch-9 hardlinked 1    3.5     3.09    0.41
Patch-9 hardlinked 2    3.52    3.21    0.29
Patch-9 hardlinked 3    3.5     3.15    0.34
                        3.51    3.15    0.35
                        126.60% 114.50% 232.69%