>From time to time I see Poul-Henning post a junior hacker assignment to this list, so I figured I'd make the same use of the bandwidth and mindshare. A while back OpenBSD "optimized" thier implementation of fdalloc() buy using a complex two level bitmask to track open slots in the descriptor table. After the implementation was ported to FreeBSD it was discovered that it actually had a negative impact on performance as world builds seemed to slow down slightly. An alternative possible optimization would be to overload the fd_ofiles array to also be a union of pointers to empty slots in the fd_ofiles array. It's not as easy as it sounds because you must make it into a doubly linked list so that entries can be removed from arbitrary locations so the freelist is kept consistant. Another trick could be overloading the fd_ofileflags to be the corresponding back-pointer, this would require that both arrays fd_ofiles and fd_ofileflags become unions and it would bloat fd_ofileflags by 4x, but that would save 25% of the bloat of doubling the size requirement of fd_ofiles. If anyone wants to take a crack at doing this it'd be interesting to see the results. I know it will cost at least doubling the size of fd_ofiles, but the speed of lookups especially for programs with a large amount of open files could be signifigant. -- -Alfred Perlstein - [[EMAIL PROTECTED]] Daemon News Magazine in your snail-mail! http://magazine.daemonnews.org/ To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
