On 2/14/2007 3:20 AM, L. Wayne Johnson wrote:
>
>>> -----Original Message-----
>>> From: Gavin Lambert [mailto:gavinl@compacsort.com]
>>> Sent: Tuesday, February 13, 2007 3:26 PM
>>> To: 'Phillip Susi'; 'Ryan Schmidt'
>>> Cc: users@subversion.tigris.org
>>> Subject: RE: Poor performance in windows. Switching back to CVS
>>>
>>> Quoth Phillip Susi <mailto:psusi@cfl.rr.com>:
>>> > If the timestamps get messed up ( and I used to see this
>>> > frequently on windows ) then all the files must be read in
>>> > full, causing the process to slow to a crawl. An svn cleanup
>>> > should fix that.
>>>
>>> Actually, on that note: if the OP has their working copy on a FAT/FAT32
>>> drive then this could cause problems. FAT only stores filestamps with a
>>> 2-second resolution, so unless software that compares timestamps knows
>>> that and specifically ignores one-second differences in the timestamp
>>> then they'll think the files have changed even when they haven't, which
>>> in SVN's case would lead to performance loss as it needs to rescan the
>>> contents of each affected file.
>>>
>>> I don't know if SVN ignores one-second differences in timestamps or not,
>>> so I don't know if it's vulnerable to this.
>
> If they are using FAT and long file names the problem is significantly worse
> than the time stamp. Long file names use multiple directory entries per
> name, the number depends on the length of the name. Not only can you get
> file fragmentation but you can get file name fragmentation as well. As files
> with different lengths names are deleted and created the names become
> interleaved and the pieces of the name can get rather far apart possible in
> a different block...
>
> Theoretically you can end up traversing the entire directory listing just to
> get a single file name.
That's not completely correct. The directory entries for one file are
always contiguous once you've put all the directory clusters together
into one big file. However, it is possible to start in one directory
cluster and continue at the start of the next one, and the free space
can become fragmented, so directories tend to grow over time: if a
filename needs 5 entries to hold it, no combination of smaller pieces
will do.
Duncan Murdoch
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Received on Wed Feb 14 20:07:24 2007