* Mat Martineau <mathewm@xxxxxxxxxxxxxx> [2011-06-30 16:36:01 -0700]: > > Hi Gustavo - > > On Thu, 30 Jun 2011, Gustavo F. Padovan wrote: > > >* Mat Martineau <mathewm@xxxxxxxxxxxxxx> [2011-06-29 14:35:19 -0700]: > > > >>Even when the received tx_seq is expected, the frame still needs to be > >>dropped if the TX window is exceeded or the receiver is in the local > >>busy state. > > > >The check doesn't mean that TX window is exceeded, it means that we have an > >invalid tx_seq and connection should be closed. I don't see the point in > >moving the expected check to after this one. > >About the local busy check. Is it worth to drop expected frames when on local > >busy? What are the advantages/disadvantages? Drop will trigger SREJ while > >Store will press the buffer. Do you have measures to prove this? > > > It's possible for expected_tx_seq to be invalid if the tx window is > full. Therefore it is important to check for an invalid tx_seq > before checking if it is expected. > > > Dropping frames during local busy is a good idea because: > > * Queuing frames during local busy ignores the receive buffer > limits requested by the application with SO_RCVBUF. This problem > gets worse with extended window sizes, where the busy_q could be > quite large > * ERTM senders are not supposed to send frames during local busy > anyway > * The spec allows for packets to be dropped in local busy (look for > "StoreOrIgnore") > > It's the memory that's most important, though. Dropping all incoming > iframes during local busy is a simple way to keep data buffer size > bounded while still allowing for larger tx windows. > > If the application can't keep up with the data rate and is > triggering local busy, throughput isn't going to be improved > significatnly by queuing those frames during local busy. You convinced me, applied! Thanks. Gustavo -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
