size of a directory Post: 57020

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Top Forums Programming size of a directory Post 57020 by AbEnd on Friday 15th of October 2004 03:18:47 PM

10-15-2004

Registered User

Quote:

Originally posted by Driver
> This definitively is I/O bound.

Irrelevant. Invoking an external program adds the time needed to create a process, execute the du program, communicate back the results and destroy the process. Whether this is going to be a problem or not depends on the application; And a portable directory traverser, once written, will compile even using only, say, DOS/Windows libraries - with minimal changes (many libraries provide the exact same functions prefixed with a ``_'' character, and/or declared in a header called direct.h instead of dirent.h)

If you mean that there is a portability issue with du, I agree with that. But spawning the sub-process will take almost no time compared to reading the directories. The overhead will never be noticeable.

Quote:

> And now that I think about it... du/fts will probably be optimized to
> run much faster than whatever could be coded trivially... Heh, what
> overhead? Not to mention du/fts will probably get right the
> traversing of the hierarchy while it is being modified. Modularity.

In think that you are dreaming this up in order to support your assertion that ``du'' is a superior solution Smilie

If you can explain how a program can ``get right the traversing of the hierarchy while it is being modified'' (and what you actually mean by that), I'm all ears. As to whether it will be ``optimized to run much faster'', well, there's not a lot of room for any relevant differences. In part because it is ``I/O bound'', as you said earlier.

1) AFAIK, it keeps opened FDs to the parent directories as it does the traversal. If some directories are moved, it will always use the right parent dir. There might be other stuff they did in fts as IIRC, there were security issues related with that as rm -r, chmod -R, find, etc, are often using fts and could be used as root on user files (ex, what happens if root does rm -rf ~user/stuff and user moves ~/stuff/a/b/c to /tmp while rm is traversing it? if using chdir ".." without checking if the parent dir is the same, it could end up traversing files starting at /. If not using "..", it will not traverse all the files in ~user/stuff because the path have changed. Keeping the open'd FD requires keeping them in dynamic data structures and this is a waste of time to code again).

2) ... Dude... It Is BECAUSE this is I/O bound that adding some CPU overhead to reduce the I/O will give a faster results. You see for yourself; they have a lot of code in that library and this is prolly not to make things slower (although a lot of it could be for security): http://www.freebsd.org/cgi/cvsweb.cg...libc/gen/fts.c

AbEnd

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LEARN ABOUT DEBIAN

dpns_getcwd

DPNS_GETCWD(3)						      DPNS Library Functions						    DPNS_GETCWD(3)

NAME

       dpns_getcwd - get DPNS current directory used by the name server

SYNOPSIS

       #include <sys/types.h>
       #include "dpns_api.h"

       char *dpns_getcwd (char *buf, int size)

DESCRIPTION

       dpns_getcwd gets the DPNS current directory used by the name server.  This current working directory is stored in a thread-safe variable in
       the client.

       If buf is not NULL, the current directory name will be stored there.
       If buf is NULL, dpns_getcwd allocates a buffer of size bytes using malloc.

       size must be at least the length of the directory name to be returned plus one byte.

RETURN VALUE

       This routine returns buf if the operation was successful or NULL if the operation failed.  In the latter case, serrno is set appropriately.

ERRORS

       ENOENT	    The current directory has not been set yet or does not exist anymore.

       ENOMEM	    buf is a NULL pointer and memory could not be allocated.

       EINVAL	    size is less than or equal to zero.

       ERANGE	    size is greater than 0 and less than size of current directory name plus 1.

       SENOSHOST    Host unknown.

       SENOSSERV    Service unknown.

       SECOMERR     Communication error.

       ENSNACT	    Name server is not running or is being shutdown.

SEE ALSO

       dpns_chdir(3)

AUTHOR

       LCG Grid Deployment Team

DPNS
							   $Date: 2001/10/04 12:12:44 $ 					    DPNS_GETCWD(3)

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