Re: Max. number of subdirectories dump

[David Holland <dholland-tech%netbsd.org@localhost>]

On Sun, Aug 18, 2013 at 06:04:55PM +0200, Johnny Billquist wrote:
 > Looking at 2.11BSD, it looks like this:
 > 
 > struct  direct {
 > [snip]
 >
 > In NetBSD (fairly current):
 > 
 > struct dirent {

careful, you want struct direct, not struct dirent:

struct  direct {
        u_int32_t d_fileno;             /* inode number of entry */
        u_int16_t d_reclen;             /* length of this record */
        u_int8_t  d_type;               /* file type, see below */
        u_int8_t  d_namlen;             /* length of string in d_name */
        char      d_name[FFS_MAXNAMLEN + 1];/* name with length <= 
FFS_MAXNAMLEN */
};

not that it's actually much different.

 > It's an obvious optimization to keep type already in the directory
 > itself. But is there any other reason why it was added there?

Speed. There's a moderately famous paper "A trace-driven analysis of
the UNIX 4.2 BSD file system" -- you might have heard of it :-)

-- 
David A. Holland
dholland%netbsd.org@localhost