Re: [rdiff-backup-users] rdiff-backup 4 windows (no cygwin needed!)

[Andrew Ferguson]

On Jun 11, 2008, at 4:51 AM, Josh Nisly wrote:
> Attached is a patch that implements the make_file_dict as described  
> above. Let me know what you think.

The patch for cmodule.c looks about right.

For rpath.py I have a concern: From earlier testing, I found try/ 
except to be about 3-4x slower than if/else, with (almost) no penalty  
if the except branch is not taken. So, although your patch would cause  
(almost) no penalty for non-Windows, there is a slow down for Windows.  
Maybe the solution is to bind the setdata function when rdiff-backup  
is loaded or connections are made (based on os.name) -- an extra round- 
trip to the remote inside the function is certainly a no-no...

Looking in the CVS logs, it looks like cmodule.c was introduced six  
years ago as an "up to 3x speed improvement". It would be interesting  
to see if that is still the case today. If it isn't, then, heck, maybe  
we can just scrap C.make_file_dict(). I think the old way breaks down  
like this:

- os.lstat()
- tuple result before network transmit <-- only necessary for Python  
2.2 compatibility
- network transmit (pickle / unpickle)
- build dictionary from result (in Python)

whereas the current method is:

- stat()
- build dictionary from result (in C)
- network transmit (pickle / unpickle)


Andrew


PS -- I also did some more testing regarding the try/except penalty:

=== foo.py ===
#!/usr/bin/python

import os

for i in range(1,5000000):
        try:
                bar = os.foo()
        except AttributeError:
                print i

=== foo2.py ===

#!/usr/bin/python

import os

for i in range(1,5000000):
        print i

=============

$ time ./foo.py > /dev/null

real            0m17.575s
user    0m17.370s
sys             0m0.138s

$ time ./foo2.py > /dev/null

real            0m3.740s
user    0m3.620s
sys             0m0.101s