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tipc: enable broadcast retrans via unicast
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In some environment, broadcast traffic is suppressed at high rate (i.e.
a kind of bandwidth limit setting). When it is applied, TIPC broadcast
can still run successfully. However, when it comes to a high load, some
packets will be dropped first and TIPC tries to retransmit them but the
packet retransmission is intentionally broadcast too, so making things
worse and not helpful at all.

This commit enables the broadcast retransmission via unicast which only
retransmits packets to the specific peer that has really reported a gap
i.e. not broadcasting to all nodes in the cluster, so will prevent from
being suppressed, and also reduce some overheads on the other peers due
to duplicates, finally improve the overall TIPC broadcast performance.

Note: the functionality can be turned on/off via the sysctl file:

echo 1 > /proc/sys/net/tipc/bc_retruni
echo 0 > /proc/sys/net/tipc/bc_retruni

Default is '0', i.e. the broadcast retransmission still works as usual.

Acked-by: Ying Xue <ying.xue@windriver.com>
Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Tuong Lien <tuong.t.lien@dektech.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Tuong Lien authored and David S. Miller committed May 26, 2020
1 parent c6ed7a5 commit a91d55d
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Showing 6 changed files with 28 additions and 11 deletions.
11 changes: 8 additions & 3 deletions net/tipc/bcast.c
Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,7 @@
#define BCLINK_WIN_MIN 32 /* bcast minimum link window size */

const char tipc_bclink_name[] = "broadcast-link";
unsigned long sysctl_tipc_bc_retruni __read_mostly;

/**
* struct tipc_bc_base - base structure for keeping broadcast send state
Expand Down Expand Up @@ -474,7 +475,7 @@ void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l,
__skb_queue_head_init(&xmitq);

tipc_bcast_lock(net);
tipc_link_bc_ack_rcv(l, acked, 0, NULL, &xmitq);
tipc_link_bc_ack_rcv(l, acked, 0, NULL, &xmitq, NULL);
tipc_bcast_unlock(net);

tipc_bcbase_xmit(net, &xmitq);
Expand All @@ -489,7 +490,8 @@ void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l,
* RCU is locked, no other locks set
*/
int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,
struct tipc_msg *hdr)
struct tipc_msg *hdr,
struct sk_buff_head *retrq)
{
struct sk_buff_head *inputq = &tipc_bc_base(net)->inputq;
struct tipc_gap_ack_blks *ga;
Expand All @@ -503,8 +505,11 @@ int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,
tipc_link_bc_init_rcv(l, hdr);
} else if (!msg_bc_ack_invalid(hdr)) {
tipc_get_gap_ack_blks(&ga, l, hdr, false);
if (!sysctl_tipc_bc_retruni)
retrq = &xmitq;
rc = tipc_link_bc_ack_rcv(l, msg_bcast_ack(hdr),
msg_bc_gap(hdr), ga, &xmitq);
msg_bc_gap(hdr), ga, &xmitq,
retrq);
rc |= tipc_link_bc_sync_rcv(l, hdr, &xmitq);
}
tipc_bcast_unlock(net);
Expand Down
4 changes: 3 additions & 1 deletion net/tipc/bcast.h
Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,7 @@ struct tipc_nl_msg;
struct tipc_nlist;
struct tipc_nitem;
extern const char tipc_bclink_name[];
extern unsigned long sysctl_tipc_bc_retruni;

#define TIPC_METHOD_EXPIRE msecs_to_jiffies(5000)

Expand Down Expand Up @@ -93,7 +94,8 @@ int tipc_bcast_rcv(struct net *net, struct tipc_link *l, struct sk_buff *skb);
void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l,
struct tipc_msg *hdr);
int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,
struct tipc_msg *hdr);
struct tipc_msg *hdr,
struct sk_buff_head *retrq);
int tipc_nl_add_bc_link(struct net *net, struct tipc_nl_msg *msg);
int tipc_nl_bc_link_set(struct net *net, struct nlattr *attrs[]);
int tipc_bclink_reset_stats(struct net *net);
Expand Down
10 changes: 6 additions & 4 deletions net/tipc/link.c
Original file line number Diff line number Diff line change
Expand Up @@ -375,7 +375,7 @@ void tipc_link_remove_bc_peer(struct tipc_link *snd_l,
snd_l->ackers--;
rcv_l->bc_peer_is_up = true;
rcv_l->state = LINK_ESTABLISHED;
tipc_link_bc_ack_rcv(rcv_l, ack, 0, NULL, xmitq);
tipc_link_bc_ack_rcv(rcv_l, ack, 0, NULL, xmitq, NULL);
trace_tipc_link_reset(rcv_l, TIPC_DUMP_ALL, "bclink removed!");
tipc_link_reset(rcv_l);
rcv_l->state = LINK_RESET;
Expand Down Expand Up @@ -2400,7 +2400,8 @@ int tipc_link_bc_sync_rcv(struct tipc_link *l, struct tipc_msg *hdr,

int tipc_link_bc_ack_rcv(struct tipc_link *r, u16 acked, u16 gap,
struct tipc_gap_ack_blks *ga,
struct sk_buff_head *xmitq)
struct sk_buff_head *xmitq,
struct sk_buff_head *retrq)
{
struct tipc_link *l = r->bc_sndlink;
bool unused = false;
Expand All @@ -2413,7 +2414,7 @@ int tipc_link_bc_ack_rcv(struct tipc_link *r, u16 acked, u16 gap,
return 0;

trace_tipc_link_bc_ack(r, acked, gap, &l->transmq);
tipc_link_advance_transmq(l, r, acked, gap, ga, xmitq, &unused, &rc);
tipc_link_advance_transmq(l, r, acked, gap, ga, retrq, &unused, &rc);

tipc_link_advance_backlog(l, xmitq);
if (unlikely(!skb_queue_empty(&l->wakeupq)))
Expand Down Expand Up @@ -2447,7 +2448,8 @@ int tipc_link_bc_nack_rcv(struct tipc_link *l, struct sk_buff *skb,
return 0;

if (dnode == tipc_own_addr(l->net)) {
rc = tipc_link_bc_ack_rcv(l, acked, to - acked, NULL, xmitq);
rc = tipc_link_bc_ack_rcv(l, acked, to - acked, NULL, xmitq,
xmitq);
l->stats.recv_nacks++;
return rc;
}
Expand Down
3 changes: 2 additions & 1 deletion net/tipc/link.h
Original file line number Diff line number Diff line change
Expand Up @@ -147,7 +147,8 @@ u16 tipc_get_gap_ack_blks(struct tipc_gap_ack_blks **ga, struct tipc_link *l,
struct tipc_msg *hdr, bool uc);
int tipc_link_bc_ack_rcv(struct tipc_link *l, u16 acked, u16 gap,
struct tipc_gap_ack_blks *ga,
struct sk_buff_head *xmitq);
struct sk_buff_head *xmitq,
struct sk_buff_head *retrq);
void tipc_link_build_bc_sync_msg(struct tipc_link *l,
struct sk_buff_head *xmitq);
void tipc_link_bc_init_rcv(struct tipc_link *l, struct tipc_msg *hdr);
Expand Down
2 changes: 1 addition & 1 deletion net/tipc/node.c
Original file line number Diff line number Diff line change
Expand Up @@ -1772,7 +1772,7 @@ static void tipc_node_bc_sync_rcv(struct tipc_node *n, struct tipc_msg *hdr,
struct tipc_link *ucl;
int rc;

rc = tipc_bcast_sync_rcv(n->net, n->bc_entry.link, hdr);
rc = tipc_bcast_sync_rcv(n->net, n->bc_entry.link, hdr, xmitq);

if (rc & TIPC_LINK_DOWN_EVT) {
tipc_node_reset_links(n);
Expand Down
9 changes: 8 additions & 1 deletion net/tipc/sysctl.c
Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,7 @@
#include "core.h"
#include "trace.h"
#include "crypto.h"

#include "bcast.h"
#include <linux/sysctl.h>

static struct ctl_table_header *tipc_ctl_hdr;
Expand Down Expand Up @@ -75,6 +75,13 @@ static struct ctl_table tipc_table[] = {
.extra1 = SYSCTL_ONE,
},
#endif
{
.procname = "bc_retruni",
.data = &sysctl_tipc_bc_retruni,
.maxlen = sizeof(sysctl_tipc_bc_retruni),
.mode = 0644,
.proc_handler = proc_doulongvec_minmax,
},
{}
};

Expand Down

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