Messages in this thread | | | Subject | Re: [PATCH v1 3/3] usb: gadget: NCM: Stop RX TCP Bursts getting dropped. | From | Eric Dumazet <> | Date | Thu, 29 May 2014 12:04:23 -0700 |
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On Thu, 2014-05-29 at 18:12 +0100, Jim Baxter wrote: > This fixes a problem with dropped packets over 16k CDC-NCM > when the connection is being heavily used. > > The issue was that the skb truesize for the unpacked NCM > packets was too high after they were cloned from the 16k > skb, this lead to the potential memory calculated by the > Kernel running out of memory earlier then it should. > > Signed-off-by: Jim Baxter <jim_baxter@mentor.com> > ---
Note the patch is OK, but changelog a bit misleading ;)
Kernel was not running out of memory, because truesize was correct.
The problem here is that a frame was consuming more kernel memory than really needed, so chances of hitting socket sk_rcvbuf limit was high.
BTW : #define NTB_OUT_SIZE 16384
alloc_skb(size) -> kmalloc(16384 + sizeof(struct skb_shared_info)) -> roundup() => 32768
So truesize of the skb was infact ~32KB, which is really insane indeed. After your patch, its back to ~2KB
Acked-by: Eric Dumazet <edumazet@google.com>
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