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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Marc Dionne , linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH net-next 4/4] rxrpc: Reduce unnecessary ack transmission Date: Wed, 8 Feb 2023 10:27:50 +0000 Message-Id: <20230208102750.18107-5-dhowells@redhat.com> In-Reply-To: <20230208102750.18107-1-dhowells@redhat.com> References: <20230208102750.18107-1-dhowells@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1757258663750268113?= X-GMAIL-MSGID: =?utf-8?q?1757258663750268113?= rxrpc_recvmsg_data() schedules an ACK to be transmitted every time at least two packets have been consumed and any time it runs out of data and would return -EAGAIN to the caller. Both events may occur within a single loop, however, and if the I/O thread is quick enough it may send duplicate ACKs. The ACKs are sent to inform the peer that more space has been made in the local Rx window, but the I/O thread is going to send an ACK every couple of DATA packets anyway, so we end up sending a lot more ACKs than we really need to. So reduce the rate at which recvmsg() schedules ACKs, such that if the I/O thread sends ACKs at its normal faster rate, recvmsg() won't actually schedule ACKs until the Rx flow stops (call->rx_consumed is cleared any time we transmit an ACK for that call, resetting the counter used by recvmsg). Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org --- net/rxrpc/recvmsg.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/rxrpc/recvmsg.c b/net/rxrpc/recvmsg.c index 50d263a6359d..76eb2b9cd936 100644 --- a/net/rxrpc/recvmsg.c +++ b/net/rxrpc/recvmsg.c @@ -137,7 +137,7 @@ static void rxrpc_rotate_rx_window(struct rxrpc_call *call) /* Check to see if there's an ACK that needs sending. */ acked = atomic_add_return(call->rx_consumed - old_consumed, &call->ackr_nr_consumed); - if (acked > 2 && + if (acked > 8 && !test_and_set_bit(RXRPC_CALL_RX_IS_IDLE, &call->flags)) rxrpc_poke_call(call, rxrpc_call_poke_idle); }