Re: [Bug-tar] Speeding up GNU tar file I/O ?

[Joerg Schilling]

"Kaveh R. Ghazi" <address@hidden> wrote:

> The fallback implementation of openat that I saw in coreutils uses
> fchdir to simulate the parent directory file descriptor argument to
> openat.  It jumps through hoops to save the CWD and restore it.  So
> you're adding several extra system calls for each fake openat.  It
> would be just as slow or most likely slower than the current mechanism
> for those platforms without a native openat.

Star is using libfind() if called with -find and libfind() uses chdir()
for traversing the tree and fchdir()  where available in order to chdir back
to the beginning.

Using fchdir in all places would either eat up fds, be slow or both.

> I'll try to measure the difference of chdir using star and see how big
> it is on older boxes.

On Solaris 11 there is no real difference.

The new method saves time at one place and takes more time at another
place. The sum is the same.

The main advantage is the features you get from the included find code.

Jörg

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