Performance problem with large-ish xml files

[blr at robertsr.us]

My repositories contain several xml files that mercurial warns me
are large (10-20 MB).

My initial commits importing from CVS were fast enough that I
wasn't too worried about speed.  But lately the speed of
committing or pushing changes to these files is approaching the
speed of CVS ci.  They sometimes take several minutes.

I manufactured a case where 90% of the lines changed and the
local commit took 35 minutes, and the push took 125 minutes.

While that is a worst case, it's bad enough to be worrisome.
These xml files are sometimes hand-edited, but occasionally
machine-generated, and a change in the code that generates
it does sometimes change the textual structure significantly.

Our pilot of mercurial was going so well, I would hate to have to
change paths now.  And I realize that hg warned me this might
happen, but is there anything I can do to make mercurial handle
these files faster?

Thanks,
Barry Roberts