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    SubjectRe: Problem: Out of memory after 2days with 2GB RAM
    On Thu, Jun 12, 2008 at 8:03 PM, Johannes Berg
    <> wrote:
    >> > Try the patch below. It should improve code generation too.
    >> >
    >> > I discussed this with Tomas previously and he says the hw is capable of
    >> > doing 20 fragments per frame (wonder why, Broadcom can do an unlimited
    >> > number...) but he complained about the networking stack not being able
    >> > to.
    >> This is scatter gather buffers that can be kicked in one DMA transaction.
    >> Well, the hardware needs to support IP checksumming for that, hence,
    >> > afaik, only two fragments can ever be used (one for hw header, one for
    >> > frame)
    >> This I still don't understand why but everybody is already tired to
    >> explaining me why.. :) Just need to find time to dig into it.
    > And you can safely decrease the allocation to 10% as I do in my patch
    > because once you understand you'll see that you cannot possibly use
    > more. Hence, you can ack this patch ;)
    >> > This cuts the allocation to 10%, or (under) a page in all cases.
    >> Probably. it would be safe to use vmalloc for allocating txb anyway.
    >> I'll give it a try.
    > Yeah, but why bother if we can just allocate 10% of the size, waste a
    > lot less memory etc. mac80211 isn't going to pass in a scatter/gather
    > frame anyway.

    Hope never dies. I actually have seen this speed up the throughput so
    I will dig into it anyway.

    >> There was already discussion on LKML about memory allocation problems
    >> on X86_64, which might explain this regression. This didn't happen
    >> before.
    > Doesn't really matter, iwlwifi is _wasting_ this allocation, it cannot
    > possibly use all those buffers anyway.

    This matter actually for consistent allocation.

    > The more interesting thing is the pci_alloc_consistent allocation right
    > below that is also _huge_, but that's because of the stupid hardware
    > design, or can the hardware cope with having the descriptors non-linear
    > in memory?

    We talk after your next HW design. How will configure 265 * 16
    descriptors separately.


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