Date: Tue, 23 Aug 2005 12:26:23 +0200 From: Divacky Roman <xdivac02@stud.fit.vutbr.cz> To: Kris Kennaway <kris@obsecurity.org> Cc: Dag-Erling Sm?rgrav <des@des.no>, current@freebsd.org Subject: Re: [PATCH]: fdalloc optimization Message-ID: <20050823102623.GA97332@stud.fit.vutbr.cz> In-Reply-To: <20050822161339.GA13907@xor.obsecurity.org> References: <20050821084546.GA77111@stud.fit.vutbr.cz> <20050821175406.GA36164@xor.obsecurity.org> <868xyu3wln.fsf@xps.des.no> <20050822161339.GA13907@xor.obsecurity.org>
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On Mon, Aug 22, 2005 at 12:13:39PM -0400, Kris Kennaway wrote: > On Mon, Aug 22, 2005 at 03:55:00PM +0200, Dag-Erling Sm?rgrav wrote: > > Kris Kennaway <kris@obsecurity.org> writes: > > > On Sun, Aug 21, 2005 at 10:45:46AM +0200, Divacky Roman wrote: > > > > I made a patch for fdalloc which could speed it up a bit, its stored under > > > > kern/85176 or http://hysteria.sk/~neologism/kern_descrip.patch > > > That's all nice and everything, but *does* it speed it up a bit? :-) > > > > It won't make a measurable difference, but that doesn't mean the patch > > is wrong. > > Just that it's not an optimization, as it was advertised :) As > Poul-Henning said, if you can't measure a performance difference > either way then sell it some other way. here is my analyze of the problem - if its correct then the patch speeds it up the code in fact looks: if (fd == fdp->fd_freefile) fdp->fd_freefile = fd_first_free(fdp, fd, fdp->fd_nfiles); fdp->fd_freefile = fd_first_free(fdp, fd, fdp->fd_nfiles); fd cannot be lower then fd_freefile (because fd is technically the first available fd) if fd > fd_freefile it makes no sense to reset it because we would make a gap in the bitarray if fd == fd_freefile we must reset it because the fd is not free anymore anyway - there is clear duplicity the fd_freefile hinting idea is quite clear (if fd_freefile is first available fd it makes sense to start searching from here cause everything before that is used) roman
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