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

[Joerg Schilling]

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

> Hi - I'd like to make a suggestion for GNU tar.
>
> I'm using tar rather often to pack and unpack large directories
> containing snapshot of code I distribute to various computers for
> testing.  On certain platforms with slow filesystems (e.g. solaris2.7)
> it takes a really long time relative to other platforms (say
> linux-gnu).  So one day I decided to run the solaris system call

Did you compare Solaris 7 to a 9 year old Linux?


> (In the above, the "..." represents read/write/close calls.)  Notice
> the system calls with really/long/path/names/being/repeated.  My
> understanding is that this can slow down I/O dramatically on some
> systems because for each such call the kernel has to stat each
> directory component of the path going through the directory hierarchy.
> Yes, modern kernels cache such lookups, but still it's better not to
> have to do it in the first place.  And some of us have to use older
> OSes which plotz.

This is definitely not causing the performance problems in GNU tar.
Check star for comparison and you will see that wihout using relative paths,
it is possible to be faster than GNU tar and with star you are even able to 
compare:

        star -c -time . > /dev/null

uses long paths, while:

        star -c -time -find . > /dev/null

uses short filenames.

Jörg

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