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packet: rollover only to socket with headroom

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Only migrate flows to sockets that have sufficient headroom, where
sufficient is defined as having at least 25% empty space.

The kernel has three different buffer types: a regular socket, a ring
with frames (TPACKET_V[12]) or a ring with blocks (TPACKET_V3). The
latter two do not expose a read pointer to the kernel, so headroom is
not computed easily. All three needs a different implementation to
estimate free space.

Tested:
  Ran bench_rollover for 10 sec with 1.5 Mpps of single flow input.

  bench_rollover has as many sockets as there are NIC receive queues
  in the system. Each socket is owned by a process that is pinned to
  one of the receive cpus. RFS is disabled. RPS is enabled with an
  identity mapping (cpu x -> cpu x), to count drops with softnettop.

    lpbb5:/export/hda3/willemb# ./bench_rollover -r -l 1000 -s
    Press [Enter] to exit

    cpu         rx       rx.k     drop.k   rollover     r.huge   r.failed
      0         16         16          0          0          0          0
      1         21         21          0          0          0          0
      2    5227502    5227502          0          0          0          0
      3         18         18          0          0          0          0
      4    6083289    6083289          0    5227496          0          0
      5         22         22          0          0          0          0
      6         21         21          0          0          0          0
      7          9          9          0          0          0          0

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Willem de Bruijn 2015-05-12 11:56:47 -04:00 committed by David S. Miller
parent 0648ab70af
commit 9954729bc3
1 changed files with 58 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

74
net/packet/af_packet.c
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@ -1234,27 +1234,68 @@ static void packet_free_pending(struct packet_sock *po)
free_percpu(po->tx_ring.pending_refcnt);
}
static bool packet_rcv_has_room(struct packet_sock *po, struct sk_buff *skb)
#define ROOM_POW_OFF 2
#define ROOM_NONE 0x0
#define ROOM_LOW 0x1
#define ROOM_NORMAL 0x2
static bool __tpacket_has_room(struct packet_sock *po, int pow_off)
{
int idx, len;
len = po->rx_ring.frame_max + 1;
idx = po->rx_ring.head;
if (pow_off)
idx += len >> pow_off;
if (idx >= len)
idx -= len;
return packet_lookup_frame(po, &po->rx_ring, idx, TP_STATUS_KERNEL);
}
static bool __tpacket_v3_has_room(struct packet_sock *po, int pow_off)
{
int idx, len;
len = po->rx_ring.prb_bdqc.knum_blocks;
idx = po->rx_ring.prb_bdqc.kactive_blk_num;
if (pow_off)
idx += len >> pow_off;
if (idx >= len)
idx -= len;
return prb_lookup_block(po, &po->rx_ring, idx, TP_STATUS_KERNEL);
}
static int packet_rcv_has_room(struct packet_sock *po, struct sk_buff *skb)
{
struct sock *sk = &po->sk;
bool has_room;
int ret = ROOM_NONE;
if (po->prot_hook.func != tpacket_rcv)
return (atomic_read(&sk->sk_rmem_alloc) + skb->truesize)
<= sk->sk_rcvbuf;
if (po->prot_hook.func != tpacket_rcv) {
int avail = sk->sk_rcvbuf - atomic_read(&sk->sk_rmem_alloc)
- skb->truesize;
if (avail > (sk->sk_rcvbuf >> ROOM_POW_OFF))
return ROOM_NORMAL;
else if (avail > 0)
return ROOM_LOW;
else
return ROOM_NONE;
}
spin_lock(&sk->sk_receive_queue.lock);
if (po->tp_version == TPACKET_V3)
has_room = prb_lookup_block(po, &po->rx_ring,
po->rx_ring.prb_bdqc.kactive_blk_num,
TP_STATUS_KERNEL);
else
has_room = packet_lookup_frame(po, &po->rx_ring,
po->rx_ring.head,
TP_STATUS_KERNEL);
if (po->tp_version == TPACKET_V3) {
if (__tpacket_v3_has_room(po, ROOM_POW_OFF))
ret = ROOM_NORMAL;
else if (__tpacket_v3_has_room(po, 0))
ret = ROOM_LOW;
} else {
if (__tpacket_has_room(po, ROOM_POW_OFF))
ret = ROOM_NORMAL;
else if (__tpacket_has_room(po, 0))
ret = ROOM_LOW;
}
spin_unlock(&sk->sk_receive_queue.lock);
return has_room;
return ret;
}
static void packet_sock_destruct(struct sock *sk)
@ -1325,12 +1366,13 @@ static unsigned int fanout_demux_rollover(struct packet_fanout *f,
unsigned int i, j;
po = pkt_sk(f->arr[idx]);
if (try_self && packet_rcv_has_room(po, skb))
if (try_self && packet_rcv_has_room(po, skb) != ROOM_NONE)
return idx;
i = j = min_t(int, po->rollover->sock, num - 1);
do {
if (i != idx && packet_rcv_has_room(pkt_sk(f->arr[i]), skb)) {
if (i != idx &&
packet_rcv_has_room(pkt_sk(f->arr[i]), skb) == ROOM_NORMAL) {
if (i != j)
po->rollover->sock = i;
return i;