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    SubjectRe: [PATCH] SLOB allocator imcompatible SLAB
    On Tue, Jun 26, 2007 at 02:06:15PM +1000, Nick Piggin wrote:
    > Yoshinori Sato wrote:
    > >At Fri, 22 Jun 2007 09:56:35 -0500,
    > >Matt Mackall wrote:
    > >
    > >>On Fri, Jun 22, 2007 at 05:08:07PM +0900, Yoshinori Sato wrote:
    > >>
    > >>>Because the page which SLOB allocator got does not have PG_slab,
    > >>
    > >>This is for a NOMMU system?
    > >
    > >
    > >Yes.
    > >
    > >
    > >>You're using an old kernel with an old version of SLOB. SLOB in newer
    > >>kernels actually sets per-page flags. Nick, can you see any reason not
    > >>to s/PG_active/PG_slab/ in the current code?
    >
    > The problem with this is that PG_private is used only for the SLOB
    > part of the allocator and not the bigblock part.

    That's fine, at least for the purposes of kobjsize. We only mark
    actual SLOB-managed pages, kobjsize assumes the rest are alloc_pages
    and that's indeed what they are.

    > We _could_ just bite the bullet and have SLOB set PG_slab, however
    > that would encouarage more users of this flag which we should hope
    > to get rid of one day.
    >
    > The real problem is that nommu wants to get the size of either
    > kmalloc or alloc_pages objects and it needs to differentiate
    > between them. So I would rather nommu to take its own page flag
    > (could overload PG_swapcache, perhaps?), and set that flag on
    > pages it allocates directly, then uses that to determine whether
    > to call ksize or not.

    I think we already established on the last go-round that the kobjsize
    scheme was rather hopelessly broken anyway.

    --
    Mathematics is the supreme nostalgia of our time.
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