DragonFly commits List (threaded) for 2005-06
Re: cvs commit: src/sys/kern imgact_elf.c init_main.c kern_checkpoint.c kern_descrip.c kern_event.c sys_generic.c sys_pipe.c uipc_syscalls.c uipc_usrreq.c vfs_aio.c vfs_syscalls.c src/sys/sys filedesc.h src/sys/dev/misc/streams streams.c ...
:On Wed, Jun 22, 2005 at 01:13:01PM +0200, Simon 'corecode' Schubert wrote:
:> Lately Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxxxxx> said:
:> > Log:
:> > File descriptor cleanup stage 2, remove the separate arrays for file
:> > pointers, fileflags, and allocation counts and replace the mess with a
:> > single structural array. Also revamp the code that checks whether the
:> > file descriptor array is built-in or allocated.
:> can anybody enlighten me why this was done in the first place?
:> this way it's much clearer anyways
:But it is also slower because the amount of data which has to be copied when
:the array is extended is now doubled. (pointer vs. struct fdnode)
Lets quantify slower.
Bytes per entry (before): 9 (three separate arrays)
Bytes per entry (after): 16 (one array of fdnodes)
Linear copy rate: 1 gigabyte sec
Do I need to continue and calculate how many nanoseconds longer
it takes to do something that isn't in the critical path?