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

[Joerg Schilling]

Paul Eggert <address@hidden> wrote:

> "Kaveh R. Ghazi" <address@hidden> writes:
>
> > Could the chdir machanism I described above be considered instead?
>
> A reasonable suggestion, but these days it might be better to use
> openat instead of chdir.  That is what CVS coreutils is doing.  (It
> uses some new gnulib code to port to systems that lack openat.)

openat() of course would be better, but it appeared 5 years ago on Solaris
and I am not sure how long for other OS to adopt.

> openat is currently only available in recent-enough versions of glibc
> and Solaris, so the code is a bit slower elsewhere, but the difference
> is not great and I don't think we need to worry overmuch about
> performance on older systems.

Yes, it is nice to see that Linux recently started to support extended attbutes 
which was the original reason for Solaris to introduce these calls. With the
support for NFSv4, more OS may also support openat() in the future.

And you are right with asuming that using openat() does not give a significant
performance improvement. With the current implementation star allows you to 
compare a chdir based implementation with a long path implementaton in one 
binary.

Compare star -c . with star -c -find .

Jörg

-- 
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