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9823f39a17
Improve ACK production by the following means:
(1) Don't send an ACK_REQUESTED ack immediately even if the RXRPC_MORE_PACKETS
flag isn't set on a data packet that has also has RXRPC_REQUEST_ACK set.
MORE_PACKETS just means that the sender just emptied its Tx data buffer.
More data will be forthcoming unless RXRPC_LAST_PACKET is also flagged.
It is possible to see runs of DATA packets with MORE_PACKETS unset that
aren't waiting for an ACK.
It is therefore better to wait a small instant to see if we can combine an
ACK for several packets.
(2) Don't send an ACK_IDLE ack immediately unless we're responding to the
terminal data packet of a call.
Whilst sending an ACK_IDLE mid-call serves to let the other side know
that we won't be asking it to resend certain Tx buffers and that it can
discard them, spamming it with loads of acks just because we've
temporarily run out of data just distracts it.
(3) Put the ACK_IDLE ack generation timeout up to half a second rather than a
single jiffy. Just because we haven't been given more data immediately
doesn't mean that more isn't forthcoming. The other side may be busily
finding the data to send to us.
Signed-off-by: David Howells <dhowells@redhat.com>
138 lines
3.6 KiB
C
138 lines
3.6 KiB
C
/* ar-skbuff.c: socket buffer destruction handling
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*
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* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/module.h>
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#include <linux/net.h>
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#include <linux/skbuff.h>
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#include <net/sock.h>
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#include <net/af_rxrpc.h>
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#include "ar-internal.h"
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/*
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* set up for the ACK at the end of the receive phase when we discard the final
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* receive phase data packet
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* - called with softirqs disabled
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*/
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static void rxrpc_request_final_ACK(struct rxrpc_call *call)
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{
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/* the call may be aborted before we have a chance to ACK it */
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write_lock(&call->state_lock);
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switch (call->state) {
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case RXRPC_CALL_CLIENT_RECV_REPLY:
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call->state = RXRPC_CALL_CLIENT_FINAL_ACK;
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_debug("request final ACK");
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/* get an extra ref on the call for the final-ACK generator to
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* release */
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rxrpc_get_call(call);
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set_bit(RXRPC_CALL_ACK_FINAL, &call->events);
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if (try_to_del_timer_sync(&call->ack_timer) >= 0)
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rxrpc_queue_call(call);
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break;
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case RXRPC_CALL_SERVER_RECV_REQUEST:
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call->state = RXRPC_CALL_SERVER_ACK_REQUEST;
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default:
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break;
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}
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write_unlock(&call->state_lock);
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}
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/*
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* drop the bottom ACK off of the call ACK window and advance the window
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*/
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static void rxrpc_hard_ACK_data(struct rxrpc_call *call,
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struct rxrpc_skb_priv *sp)
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{
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int loop;
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u32 seq;
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spin_lock_bh(&call->lock);
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_debug("hard ACK #%u", ntohl(sp->hdr.seq));
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for (loop = 0; loop < RXRPC_ACKR_WINDOW_ASZ; loop++) {
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call->ackr_window[loop] >>= 1;
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call->ackr_window[loop] |=
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call->ackr_window[loop + 1] << (BITS_PER_LONG - 1);
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}
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seq = ntohl(sp->hdr.seq);
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ASSERTCMP(seq, ==, call->rx_data_eaten + 1);
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call->rx_data_eaten = seq;
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if (call->ackr_win_top < UINT_MAX)
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call->ackr_win_top++;
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ASSERTIFCMP(call->state <= RXRPC_CALL_COMPLETE,
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call->rx_data_post, >=, call->rx_data_recv);
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ASSERTIFCMP(call->state <= RXRPC_CALL_COMPLETE,
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call->rx_data_recv, >=, call->rx_data_eaten);
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if (sp->hdr.flags & RXRPC_LAST_PACKET) {
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rxrpc_request_final_ACK(call);
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} else if (atomic_dec_and_test(&call->ackr_not_idle) &&
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test_and_clear_bit(RXRPC_CALL_TX_SOFT_ACK, &call->flags)) {
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/* We previously soft-ACK'd some received packets that have now
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* been consumed, so send a hard-ACK if no more packets are
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* immediately forthcoming to allow the transmitter to free up
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* its Tx bufferage.
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*/
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_debug("send Rx idle ACK");
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__rxrpc_propose_ACK(call, RXRPC_ACK_IDLE, sp->hdr.serial,
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false);
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}
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spin_unlock_bh(&call->lock);
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}
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/*
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* destroy a packet that has an RxRPC control buffer
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* - advance the hard-ACK state of the parent call (done here in case something
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* in the kernel bypasses recvmsg() and steals the packet directly off of the
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* socket receive queue)
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*/
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void rxrpc_packet_destructor(struct sk_buff *skb)
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{
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struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
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struct rxrpc_call *call = sp->call;
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_enter("%p{%p}", skb, call);
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if (call) {
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/* send the final ACK on a client call */
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if (sp->hdr.type == RXRPC_PACKET_TYPE_DATA)
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rxrpc_hard_ACK_data(call, sp);
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rxrpc_put_call(call);
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sp->call = NULL;
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}
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if (skb->sk)
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sock_rfree(skb);
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_leave("");
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}
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/**
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* rxrpc_kernel_free_skb - Free an RxRPC socket buffer
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* @skb: The socket buffer to be freed
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*
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* Let RxRPC free its own socket buffer, permitting it to maintain debug
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* accounting.
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*/
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void rxrpc_kernel_free_skb(struct sk_buff *skb)
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{
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rxrpc_free_skb(skb);
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}
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EXPORT_SYMBOL(rxrpc_kernel_free_skb);
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