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    SubjectRe: [PATCH v2 1/3] virtio_net: Split receive buffer alloc/add
    On Tue, Jan 10, 2012 at 5:30 PM, Rusty Russell <rusty@rustcorp.com.au> wrote:
    > On Tue, 10 Jan 2012 09:41:01 -0800, Mike Waychison <mikew@google.com> wrote:
    >> In preparation for allocating receive buffers in the slow path without
    >> disabling NAPI, split the allocation and addition of receive buffers
    >> apart into two separate functions (per receive buffer type).
    >>
    >> While here, move the vi->num accounting into the add functions.
    >>
    >> Signed-off-by: Mike Waychison <mikew@google.com>
    >
    > Hi Mike...
    >
    >        This exposes a nasty ugliness in the way virtio_net works.  We
    > allocate an skbuff for the small packet case, and just allocate the
    > pages for the large packet cases, and alloc the skbuff when we fill the
    > pages.
    >
    >        I think all the allocators should return a populated skbuff;
    > this uses a bit more memory in theory, but should make the code simpler.
    > As an added bonus, your life should get much simpler for these patches.
    >
    > I'll try to create such a patch tonight, but I'm busy finalizing my
    > linux.conf.au presentation, so it might take longer :(
    >

    This seems reasonable for the "big" receive buffers, but I don't think
    it makes a lot of sense for "mergeable" receive buffers as best I can
    tell. Hopefully making this work isn't too hard though :)
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