Re: fdesc allocation optimization

From: Andre Oppermann (andre_at_freebsd.org)
Date: 08/22/05

  • Next message: Dag-Erling Smørgrav: "Re: fdesc allocation optimization" 
    Date: Mon, 22 Aug 2005 15:40:39 +0200
To: Dag-Erling Smørgrav <des@des.no>

    Dag-Erling Smørgrav wrote:
    >
    > Alexey Dokuchaev <danfe@FreeBSD.org> writes:
    > > i've been browsing some of dfbsd resources recently, and found this one
    > > being pretty interesting:
    > >
    > > http://leaf.dragonflybsd.org/mailarchive/commits/2005-06/msg00526.html
    > >
    > > however, it seemingly did not get attention in our lists. so i am
    > > wondering if there are work/plans on porting hsu@'s work? i remember
    > > that at some point we adopted some openbsd-derived algorithm, but since
    > > matt states that this is "far better algorithm then anything we or
    > > freebsd thought up before", i figured it worth a look.
    >
    > Bollocks. Our current algorithm (which I wrote) is so fast you don't
    > even notice it's there. It's actually simpler than the OpenBSD code
    > from which it was inspired, and in theory it should be slower, but I
    > discovered that the overhead of the "better" algorithm was so high
    > that it consistently lost to the simpler one for reasonable amounts of
    > file descriptors (up to about 100,000 per process).
    >
    > The source code for the microbenchmark I used, and selected graphs
    > comparing my code to the previous implementation, are available at
    > <URL:http://people.freebsd.org/~des/fdbench/>.

    Wow, impressive!

    > (the strange artifacts you see on the red graphs are the result of the
    > file descriptor table overrunning the CPU cache)

    When did you commit this? Is it only in post 5.0 releases? 

    -- 
Andre
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