Date: Sun, 23 Apr 2006 23:55:23 -0700 From: Julian Elischer <julian@elischer.org> To: John-Mark Gurney <gurney_j@resnet.uoregon.edu> Cc: Kirk McKusick <mckusick@McKusick.COM>, arch@freebsd.org Subject: Re: Linus Torvalds on FreeBSD's Use of Copy-on-write Message-ID: <444C765B.7070803@elischer.org> In-Reply-To: <20060424064352.GA728@funkthat.com> References: <200604240633.k3O6XUJ0042841@chez.mckusick.com> <20060424064352.GA728@funkthat.com>
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John-Mark Gurney wrote: >Kirk McKusick wrote this message on Sun, Apr 23, 2006 at 23:33 -0700: > > >>Linus explained that while this may look good on specific benchmarks, >>it actually introduces extra overhead, "the thing is, the cost of >> >> > >Has he benchmarked this to prove his point? And has he done it over >realworld work loads, like Apache or another "standard" program instead >of a microbenchmark designed especially to make COW look bad? > > Well no-one has even confirmed that freeBSD does all this "page flipping" etc. I doubt that Linus has looked inside the BSD kernels. He's probably just repeating what he's been told, and that's so accurate, right? I know that freeBSD developers have over the last few years also acknowledged that the speed of modern CPUs vs. memeory speeds makes it often less efficient to do certain optimisations than it used to be. >As w/ all theories, w/o numbers, they are only theories till backed up >w/ benchmarks. > >This isn't suppose to defend COW, but it is designed to ensure that >people don't stop exploring just because someone says something... > > >
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