diff options
| author | Oliver Hartkopp <socketcan@hartkopp.net> | 2014-04-02 20:25:26 +0200 |
|---|---|---|
| committer | Marc Kleine-Budde <mkl@pengutronix.de> | 2014-05-19 09:38:24 +0200 |
| commit | 45c700291aee5170185bf5d1c2a494b1e3fe0883 (patch) | |
| tree | 296c18dc3657954ecf84a51c588046e855f2d9cd /net/can/af_can.c | |
| parent | e3d3917f3d8f624a8df567b581fd8c4da49b443f (diff) | |
can: add hash based access to single EFF frame filters
In contrast to the direct access to the single SFF frame filters (which are
indexed by the SFF CAN ID itself) the single EFF frame filters are arranged
in a single linked hlist. To reduce the hlist traversal in the case of many
filter subscriptions a hash based access is introduced for single EFF filters.
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Diffstat (limited to 'net/can/af_can.c')
| -rw-r--r-- | net/can/af_can.c | 31 |
1 files changed, 26 insertions, 5 deletions
diff --git a/net/can/af_can.c b/net/can/af_can.c index a27f8aad9e99..ce82337521f6 100644 --- a/net/can/af_can.c +++ b/net/can/af_can.c @@ -338,6 +338,29 @@ static struct dev_rcv_lists *find_dev_rcv_lists(struct net_device *dev) } /** + * effhash - hash function for 29 bit CAN identifier reduction + * @can_id: 29 bit CAN identifier + * + * Description: + * To reduce the linear traversal in one linked list of _single_ EFF CAN + * frame subscriptions the 29 bit identifier is mapped to 10 bits. + * (see CAN_EFF_RCV_HASH_BITS definition) + * + * Return: + * Hash value from 0x000 - 0x3FF ( enforced by CAN_EFF_RCV_HASH_BITS mask ) + */ +static unsigned int effhash(canid_t can_id) +{ + unsigned int hash; + + hash = can_id; + hash ^= can_id >> CAN_EFF_RCV_HASH_BITS; + hash ^= can_id >> (2 * CAN_EFF_RCV_HASH_BITS); + + return hash & ((1 << CAN_EFF_RCV_HASH_BITS) - 1); +} + +/** * find_rcv_list - determine optimal filterlist inside device filter struct * @can_id: pointer to CAN identifier of a given can_filter * @mask: pointer to CAN mask of a given can_filter @@ -400,10 +423,8 @@ static struct hlist_head *find_rcv_list(canid_t *can_id, canid_t *mask, !(*can_id & CAN_RTR_FLAG)) { if (*can_id & CAN_EFF_FLAG) { - if (*mask == (CAN_EFF_MASK | CAN_EFF_RTR_FLAGS)) { - /* RFC: a future use-case for hash-tables? */ - return &d->rx[RX_EFF]; - } + if (*mask == (CAN_EFF_MASK | CAN_EFF_RTR_FLAGS)) + return &d->rx_eff[effhash(*can_id)]; } else { if (*mask == (CAN_SFF_MASK | CAN_EFF_RTR_FLAGS)) return &d->rx_sff[*can_id]; @@ -632,7 +653,7 @@ static int can_rcv_filter(struct dev_rcv_lists *d, struct sk_buff *skb) return matches; if (can_id & CAN_EFF_FLAG) { - hlist_for_each_entry_rcu(r, &d->rx[RX_EFF], list) { + hlist_for_each_entry_rcu(r, &d->rx_eff[effhash(can_id)], list) { if (r->can_id == can_id) { deliver(skb, r); matches++; |