In this message
http://subversion.tigris.org/servlets/ReadMsg?list=dev&msgNo=35002
Ben Collins-Sussman described how adding eol translation to his tiny &
speedy export editor slowed it back down to almost exactly the same
speed as a regular checkout. Since the only change he made was to add
translation, it seems likely (ahem) that the cause is
svn_subst_translate_stream(), which reads data in one byte at a time:
while (err == SVN_NO_ERROR)
{
/* Read a byte from SRC */
readlen = 1;
read_err = svn_stream_read (s, &c, &readlen);
[...]
}
This implies that the translation step is by far our costliest
bottleneck in many working copy operations (and that reading & writing
the various .svn/* files may not be as much of a problem as we thought.)
This also explains why we've been seeing checkouts and updates slow
down over time -- we've been adding eol properties to more and more
files in the Subversion tree.
There is no reason we can't read much bigger blocks in that loop.
Assigning to self, I want to see this happen real bad... :-)
Improvement
Major