Re: [Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19

From: Mel Gorman (mel_at_csn.ul.ie)
Date: 11/04/05

  • Next message: Herbert Xu: "Re: do_sendfile ppos check ..."
    Date:	Fri, 4 Nov 2005 02:35:09 +0000 (GMT)
    To: Nick Piggin <nickpiggin@yahoo.com.au>
    
    

    On Fri, 4 Nov 2005, Nick Piggin wrote:

    > Mel Gorman wrote:
    > > On Fri, 4 Nov 2005, Nick Piggin wrote:
    > >
    > > Todays massive machines are tomorrows desktop. Weak comment, I know, but
    > > it's happened before.
    > >
    >
    > Oh I wouldn't bet against it. And if desktops of the future are using
    > 100s of GB then they probably would be happy to use 64K pages as well.
    >

    And would it not be nice to be ready when it happens, before it happens
    even?

    > >
    > > > Maybe the solution is to bloat the kernel sources enough to make
    > > > 64KB pages worthwhile?
    > > >
    > >
    >
    > Sorry this wasn't meant to be a dig at your patches - I guess it turned
    > out that way though :\
    >

    Oh, I'll live. If I was going to take it personally and go into a big
    sulk, I wouldn't be here. This is linux-kernel, not the super-friends
    club.

    > But yes, if anybody is adding complexity or size to core code it
    > obviously does need to be justified -- and by no means does this only
    > apply to you.
    >

    I've tried to justify it with benchmarks that came with each release and
    code reviews, particularly by Dave Hansen, showed that earlier versions
    had significant problems that needed to be ironed out. I don't want to
    hurt the normal case, because the fact of the matter is, my desktop
    machine (which runs with these patches to see if there are any bugs)
    runs the normal case and it will until we get much further because I'm not
    configuring my machine for HugeTLB when it boots. If I'm hurting the
    normal case, that's more time switching windows to see if the next test
    kernel has built yet.

    If we can do this and not regress in the standard case, then what is
    wrong? I'm still waiting for figures that say this approach is slow and I
    can only assume someone is trying considering the length of this thread.
    If and when those figures show up, I'll put on the thinking hat and see
    where I went wrong because regression performance is wrong. There is a
    win-win solution somewhere, how hard could it possibly be :) ?

    I'm looking at the zone approach. I want to see if it can work in a nice
    fashion, not in a "if the sysadm can see the future and configure
    correctly, it'll work just fine" fashion. I'm not confident, but it might
    be bias.

    -- 
    Mel Gorman
    Part-time Phd Student                          Java Applications Developer
    University of Limerick                         IBM Dublin Software Lab
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  • Next message: Herbert Xu: "Re: do_sendfile ppos check ..."

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