This is the mail archive of the cygwin mailing list for the Cygwin project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: Making /bin/sh == bash. Has the time come?


On Sun, Jun 12, 2005 at 09:48:25PM -0500, Gary R. Van Sickle wrote:
>>Can I just ask a basic question here?  So if both ash and bash are
>>using the same method of execution (fork), is the reason for bash's
>>slowness due to it just being a larger program with more pages to copy
>>during a fork()?
>
>Fork() also has to dup any and all handles/descriptors/etc, which takes
>all kinds of time.

Actually most handles are just inherited.  Only some of them have to be
duped or recreated -- ttys and sockets are the most notable exceptions.
Some close-on-exec'ed fds have to be closed, too.  With the advent of
the cygheap, most of the inherited information is just one large
"ReadProcessMemory" with a fixups for problematic stuff like sockets.

There are all sorts of other things that fork does, though, like making
half-hearted attempts to load dlls in the same location in the child as
they were in the parent, fixing up mmaps, maintaining a list of handles
to slow pid reuse for bash (is that still needed?), etc.

cgf

--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Problem reports:       http://cygwin.com/problems.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]