[CCID 3]: Use a function to update p_inv, and p is never used
This
1) concentrates previously scattered computation of p_inv into one function;
2) removes the `p' element of the CCID3 RX sock (it is redundant);
3) makes the tfrc_rx_info structure standalone, only used on demand.
The reason for (2) is that the code essentially only uses p_inv = 1/p. It does
not
need p, since all the relevant information is already in p_inv.
The motivation for (3) is that the embedded info structure will not be used
often,
so that the extra cost of keeping p in synch with p_inv (which has to be done at
each packet reception) is overhead most of the time.
Advantages that this buys:
--------------------------
* the RX sock loses further weight;
* computation of p_inv is no longer scattered in different places;
* not having to keep p in sync with p_inv speeds up computation
(important, as p_inv has to be recomputed for each new data packet);
* several test cases can now be removed since all is in one function;
* the send_feedback and packet_recv code becomes simpler.
Signed-off-by: Gerrit Renker <[EMAIL PROTECTED]>
---
net/dccp/ccids/ccid3.c | 57 +++++++++++++++++++++++++------------------------
net/dccp/ccids/ccid3.h | 19 ++++++----------
2 files changed, 38 insertions(+), 38 deletions(-)
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -726,6 +726,25 @@ static inline void ccid3_hc_rx_update_s(
TFRC_EWMA(hcrx->ccid3hcrx_s, len, 9);
}
+/* returns: 1 when p > p_prev (i.e. when feedback is required); 0 else */
+static int ccid3_hc_rx_update_p(struct ccid3_hc_rx_sock *hcrx)
+{
+ struct list_head *li_hist = &hcrx->ccid3hcrx_li_hist;
+ u32 pinv_prev = hcrx->ccid3hcrx_pinv;
+
+ if (list_empty(li_hist)) /* only empty if no loss so far, i.e. p == 0 */
+ return 0;
+
+ hcrx->ccid3hcrx_pinv = dccp_li_hist_calc_i_mean(li_hist);
+ if (hcrx->ccid3hcrx_pinv == 0) {
+ DCCP_BUG("non-empty LI history and yet I_mean == 0!");
+ return 0;
+ }
+
+ /* exploit that p > p_prev <=> 1/p < 1/p_prev */
+ return (hcrx->ccid3hcrx_pinv < pinv_prev);
+}
+
static void ccid3_hc_rx_send_feedback(struct sock *sk)
{
struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
@@ -741,6 +760,7 @@ static void ccid3_hc_rx_send_feedback(st
switch (hcrx->ccid3hcrx_state) {
case TFRC_RSTATE_NO_DATA:
hcrx->ccid3hcrx_x_recv = 0;
+ hcrx->ccid3hcrx_pinv = ~0U; /* see RFC 4342, 8.5 */
break;
case TFRC_RSTATE_DATA:
delta = timeval_delta(&now,
@@ -770,14 +790,6 @@ static void ccid3_hc_rx_send_feedback(st
DCCP_BUG_ON(delta < 0);
hcrx->ccid3hcrx_elapsed_time = delta / 10;
- if (hcrx->ccid3hcrx_p == 0)
- hcrx->ccid3hcrx_pinv = ~0U; /* see RFC 4342, 8.5 */
- else if (hcrx->ccid3hcrx_p > 1000000) {
- DCCP_WARN("p (%u) > 100%%\n", hcrx->ccid3hcrx_p);
- hcrx->ccid3hcrx_pinv = 1; /* use 100% in this case */
- } else
- hcrx->ccid3hcrx_pinv = 1000000 / hcrx->ccid3hcrx_p;
-
dp->dccps_hc_rx_insert_options = 1;
dccp_send_ack(sk);
}
@@ -1016,7 +1028,7 @@ static void ccid3_hc_rx_packet_recv(stru
const struct dccp_options_received *opt_recv;
struct dccp_rx_hist_entry *packet;
struct timeval now;
- u32 p_prev, r_sample, rtt_prev;
+ u32 r_sample, rtt_prev;
int loss, payload_size;
BUG_ON(hcrx == NULL);
@@ -1096,22 +1108,8 @@ static void ccid3_hc_rx_packet_recv(stru
ccid3_pr_debug("%s(%p, state=%s), data loss! Reacting...\n",
dccp_role(sk), sk, dccp_state_name(sk->sk_state));
- p_prev = hcrx->ccid3hcrx_p;
-
- /* Calculate loss event rate */
- if (!list_empty(&hcrx->ccid3hcrx_li_hist)) {
- u32 i_mean = dccp_li_hist_calc_i_mean(&hcrx->ccid3hcrx_li_hist);
-
- /* Scaling up by 1000000 as fixed decimal */
- if (i_mean != 0)
- hcrx->ccid3hcrx_p = 1000000 / i_mean;
- } else
- DCCP_BUG("empty loss history");
-
- if (hcrx->ccid3hcrx_p > p_prev) {
+ if (ccid3_hc_rx_update_p(hcrx))
ccid3_hc_rx_send_feedback(sk);
- return;
- }
}
static int ccid3_hc_rx_init(struct ccid *ccid, struct sock *sk)
@@ -1165,6 +1163,11 @@ static int ccid3_hc_rx_getsockopt(struct
{
const struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
const void *val;
+ struct tfrc_rx_info rx_info = {
+ .tfrcrx_x_recv = hcrx->ccid3hcrx_x_recv,
+ .tfrcrx_rtt = hcrx->ccid3hcrx_rtt,
+ .tfrcrx_p = scaled_div(1, hcrx->ccid3hcrx_pinv)
+ };
/* Listen socks doesn't have a private CCID block */
if (sk->sk_state == DCCP_LISTEN)
@@ -1172,10 +1175,10 @@ static int ccid3_hc_rx_getsockopt(struct
switch (optname) {
case DCCP_SOCKOPT_CCID_RX_INFO:
- if (len < sizeof(hcrx->ccid3hcrx_tfrc))
+ if (len < sizeof(rx_info))
return -EINVAL;
- len = sizeof(hcrx->ccid3hcrx_tfrc);
- val = &hcrx->ccid3hcrx_tfrc;
+ len = sizeof(rx_info);
+ val = &rx_info;
break;
default:
return -ENOPROTOOPT;
--- a/net/dccp/ccids/ccid3.h
+++ b/net/dccp/ccids/ccid3.h
@@ -127,38 +127,35 @@ enum ccid3_hc_rx_states {
/** struct ccid3_hc_rx_sock - CCID3 receiver half-connection socket
*
- * @ccid3hcrx_x_recv - Receiver estimate of send rate (RFC 3448 4.3)
- * @ccid3hcrx_rtt - Receiver estimate of rtt (non-standard)
- * @ccid3hcrx_p - current loss event rate (RFC 3448 5.4)
* @ccid3hcrx_seqno_nonloss - Last received non-loss sequence number
* @ccid3hcrx_ccval_nonloss - Last received non-loss Window CCVal
* @ccid3hcrx_ccval_last_counter - Tracks window counter (RFC 4342, 8.1)
* @ccid3hcrx_state - receiver state, one of %ccid3_hc_rx_states
+ * @ccid3hcrx_s - Received packet size in bytes
* @ccid3hcrx_bytes_recv - Total sum of DCCP payload bytes
+ * @ccid3hcrx_x_recv - Receiver estimate of send rate (RFC 3448, sec. 4.3)
+ * @ccid3hcrx_rtt - Receiver estimate of rtt (non-standard)
+ * @ccid3hcrx_pinv - Reciprocal of Loss Event Rate p (RFC 4342, sec. 8.5)
* @ccid3hcrx_tstamp_last_feedback - Time at which last feedback was sent
* @ccid3hcrx_tstamp_last_ack - Time at which last feedback was sent
* @ccid3hcrx_hist - Packet history
* @ccid3hcrx_li_hist - Loss Interval History
- * @ccid3hcrx_s - Received packet size in bytes
- * @ccid3hcrx_pinv - Inverse of Loss Event Rate (RFC 4342, sec. 8.5)
* @ccid3hcrx_elapsed_time - Time since packet reception
*/
struct ccid3_hc_rx_sock {
- struct tfrc_rx_info ccid3hcrx_tfrc;
-#define ccid3hcrx_x_recv ccid3hcrx_tfrc.tfrcrx_x_recv
-#define ccid3hcrx_rtt ccid3hcrx_tfrc.tfrcrx_rtt
-#define ccid3hcrx_p ccid3hcrx_tfrc.tfrcrx_p
u64 ccid3hcrx_seqno_nonloss:48,
ccid3hcrx_ccval_nonloss:4,
ccid3hcrx_ccval_last_counter:4;
enum ccid3_hc_rx_states ccid3hcrx_state:8;
+ u16 ccid3hcrx_s;
u32 ccid3hcrx_bytes_recv;
+ u32 ccid3hcrx_x_recv;
+ u32 ccid3hcrx_rtt;
+ u32 ccid3hcrx_pinv;
struct timeval ccid3hcrx_tstamp_last_feedback;
struct timeval ccid3hcrx_tstamp_last_ack;
struct list_head ccid3hcrx_hist;
struct list_head ccid3hcrx_li_hist;
- u16 ccid3hcrx_s;
- u32 ccid3hcrx_pinv;
u32 ccid3hcrx_elapsed_time;
};
-
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