From: Christopher Faylor <cgf@redhat.com>
To: cygwin@cygwin.com
Subject: Re: Followup on eliminating symlink ReadFile calls -- it's not necessary
Date: Wed, 14 Feb 2001 13:12:00 -0000 [thread overview]
Message-ID: <20010214161306.D18567@redhat.com> (raw)
In-Reply-To: <20010214174608.17253.qmail@lizard.curl.com>
On Wed, Feb 14, 2001 at 12:46:08PM -0500, Jonathan Kamens wrote:
>DJ Delorie suggested using "mount -x" to eliminate the ReadFile for
>determining whether a file is executable, and adding a new mount
>option to indicate that there are no symbolic links under a particular
>mountpoint, to eliminate the other ReadFile.
>
>I implemented his suggestion, adding a "-l" flag and a corresponding
>MOUNT_NO_SYMLINKS flag, and did some performance testing on the
>result. I was surprise to discover that mounting with this option
>didn't provide any additional performance improvement over "-x".
Actually, I suggested this.
>This inspired me to do a more careful reading of the code, at which
>point I noticed what I should have noticed before -- the ReadFile to
>check for a symbolic link doesn't happen unless the system attribute
>is set on a file. In other words, the performance hit we were seeing
>in Make was due entirely to the ReadFile checking for executability,
>NOT to the ReadFile checking for symbolic links.
I also mentioned that two ReadFiles were not happening for stat()
so this should not be a surprise.
>Therefore, the current Cygwin already has the ability to eliminate this
>performance hit -- you just need to mount filesystems with "-x", and no
>additional changes to Cygwin are necessary.
>
>Thanks to everyone who responded to my messages yesterday offering
>suggestions that helped me track this down.
>
>Given the magnitude of the performance improvement when "-x" is used, I
>wonder if its use should be recommended in the documentation, or
>perhaps it should even be the default behavior.
Setting execute permissions on everything is not a generically good
solution. It means that cygwin will try to execute things like "foo.c".
I've mentioned that -x is a performance win in the mailing list several
times. The old version of setup.exe used to set this for /bin and
/usr/bin. I don't know if the current version does or not.
cgf
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next prev parent reply other threads:[~2001-02-14 13:12 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-02-14 9:46 Jonathan Kamens
2001-02-14 13:12 ` Christopher Faylor [this message]
2001-02-14 16:06 ` Jonathan Kamens
2001-02-14 17:48 ` Charles S. Wilson
2001-02-15 5:57 ` Jonathan Kamens
2001-02-15 9:49 ` Christopher Faylor
2001-02-15 11:49 ` Warren Young
2001-02-15 14:27 ` Christopher Faylor
2001-02-15 15:17 ` David Starks-Browning
2001-02-15 16:37 ` Christopher Faylor
2001-02-16 0:46 ` Corinna Vinschen
2001-02-16 1:39 ` Warren Young
2001-02-16 8:59 ` Christopher Faylor
2001-02-14 19:16 ` Christopher Faylor
2001-02-15 6:07 ` Jonathan Kamens
2001-02-15 11:56 ` Warren Young
2001-02-15 1:28 Robert Melchers
[not found] <md5:6ACE45F554B052AAC9BD9700033B10F9>
2001-02-15 5:48 ` Earnie Boyd
2001-02-15 7:02 Robert Melchers
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