Subject: diff can be slow
From: <[email-masked]>
To: <[email-masked]>
Cc: <[email-masked]>
Date: Sun, 31 Oct 2004 12:00:51 -0000

If it helps I will be more specific (versions, cygcheck.out, etc) in a
follow-up communication but for the moment could I just investigate whether
this sort of behaviour is familiar to anybody else? I seem to remember
seeing a post reporting something similar and non-specific a while ago, but
can locate neither it nor any response to it.
I frequently need to compare the contents of entire drives, achieved with
	diff -rq /cygdrive/c/ /cygdrive/f/
and where the contents common to both drives may be as much as 30G. It turns
out that this comparison is sometimes achieved very rapidly (a few minutes,
like 5) and the identical comparison performed half a day later might still
be churning away after 60 minutes. I think it is fast if the diff command is
the first thing I do after starting Cygwin AND if that Cygwin session is the
first since switching on. It may be slow if it is the first Cygwin activity
but not the first Cygwin session. I think it is often slow if it is not the
first Cygwin activity in a Cygwin session. In any case, if the diff takes
long enough for the screensaver to start, then after moving the mouse,
recovery of the desktop and the Cygwin active window can take _ages_. It
seems to me that "diff" itself hogs performance, and that under other
circumstances the performance available to "diff" even before starting, is
somehow strangely reduced.
Sorry. If this was easy to describe I would have made a better job of it.
But the behaviour I have described is intensely frustrating. I can put up
with slow performance and often have to, but not when that performance is so
variable and sometimes lightning fast.
Any ideas?
Thanks,
Fergus

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