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Re: higher-level IO very slow with cygwin1.dll 5.10 (due to set_flags?)


Thanks to those who responded to my post.

I am not sure though if all of you read the
entire sequence of the thread.

In my first post, I did attach an excerpt
from an strace dump of a sample program that
seemed to show "where the time is going".

Here is the relevant information again in case
it was missed the first time (showing longest
operations in the strace dump):

171674 127276583 [main] test1 613445 fhandler_base::set_flags: flags 0x110000, supplied_bin 0x0
158323 5071628 [main] test1 613445 fhandler_base::set_flags: flags 0x110000, supplied_bin 0x0
144645 74466322 [main] test1 613445 fhandler_base::set_flags: flags 0x110000, supplied_bin 0x0
133088 111148059 [main] test1 613445 fhandler_base::set_flags: flags 0x110000, supplied_bin 0x0
118305 4774629 [main] test1 613445 fhandler_base::set_flags: flags 0x110000, supplied_bin 0x0
115336 6690357 [main] test1 613445 fhandler_base::set_flags: flags 0x110000, supplied_bin 0x0
114418 79036229 [main] test1 613445 fhandler_base::set_flags: flags 0x110000, supplied_bin 0x0
113172 69211692 [main] test1 613445 fhandler_base::set_flags: flags 0x110000, supplied_bin 0x0
112608 6888268 [main] test1 613445 fhandler_base::set_flags: flags 0x110000, supplied_bin 0x0
108520 47854275 [main] test1 613445 fhandler_base::set_flags: flags 0x110000, supplied_bin 0x0
107589 6137061 [main] test1 613445 fhandler_base::set_flags: flags 0x110000, supplied_bin 0x0
106538 69397028 [main] test1 613445 fhandler_base::set_flags: flags 0x110000, supplied_bin 0x0
106369 1959755 [main] test1 613445 fhandler_base::set_flags: flags 0x110000, supplied_bin 0x0
100002 67943460 [main] test1 613445 fhandler_base::set_flags: flags 0x110000, supplied_bin 0x0
99220 64838744 [main] test1 613445 setmode_helper: improbable, but 2 != 3
96976 110763753 [main] test1 613445 setmode_helper: improbable, but 0 != 3


The program I am tracing simply opens a large file
(about 7 MB) with fopen and then reads characters
from it with getc, and does nothing else.

It takes about 10-20 times longer than a
program which opens the same file with open
and reads it with read. In the strace of this
faster program, the time is dominated by calls
to readv.

In my original post I also included the
output of cygcheck on my system. Please
advise if I should post this again.

Also if it would help to see the lines in the
strace dump in context, as opposed to sorted
by duration of each operation, I could post
that.

Based on the instructions listed at the
problems.html webpage on the Cygwin site,
I thought this was sufficient information
to begin a request for assistance. I do
not really understand what you are advising
me to do beyond this when you say I
should "debug cygwin". I sure would
appreciate some guidance in how to do this.

Possibly I should add that I am comparing
the behavior of version 1.5.10 to a much
older version that I was using before. So
whatever is causing this odd behavior on
my system may not be a feature that was new
to version 1.5.10. I am thinking somehow
that it might in fact have something to do
with how mounts are handled differently
in more recent versions. Previously I did
not have to mount any directories, now
though I am having trouble finding any
set of mount commands that will allow me
to open files in text mode by default,
which was how the earlier version of cygwin
I had worked. Nor does setting the CYGWIN
environment variable to nobinmode seem to
have any effect.

Thanks again for any help


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