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Message-ID: <AANLkTinRFfXv_cqE92f7Kz=1V8Hf_byxeUur0Bwp_OL_@mail.gmail.com>
Date: Fri, 11 Mar 2011 11:26:42 -0500
From: Sangtae Ha <sangtae.ha@...il.com>
To: Stephen Hemminger <shemminger@...tta.com>
Cc: davem@...emloft.net, rhee@...u.edu, netdev@...r.kernel.org
Subject: Re: [PATCH 5/6] tcp_cubic: fix clock dependency
Thanks Stephen.
The patch is useful since I had to increase CA_PRIV_SIZE to use
ktime_t for the testing.
Indeed, CUBIC already used up the limit CA_PRIV_SIZE for its variables.
I've got compilation errors because of "jiffies_to_ms" and I corrected
it to "jiffies_to_msecs"
- return jiffies_to_ms(jiffies);
+ return jiffies_to_msecs(jiffies);
Also, >= instead of <=, which Lucas already found and reported.
- if ((s32)(now - ca->round_start) <= ca->delay_min >> 4)
+ if ((s32)(now - ca->round_start) >= ca->delay_min >> 4)
Sangtae
On Thu, Mar 10, 2011 at 11:51 AM, Stephen Hemminger
<shemminger@...tta.com> wrote:
> The hystart code was written with assumption that HZ=1000.
> Replace the use of jiffies with bictcp_clock as a millisecond
> real time clock.
>
> Warning: this is still experimental, there may still be mistakes
> in units (ms vs. jiffies).
>
> Signed-off-by: Stephen Hemminger <shemminger@...tta.com>
>
> P.s: tried using ktime_t but 'struct bictcp' is bumping against limit
> of CA_PRIV_SIZE.
>
> --- a/net/ipv4/tcp_cubic.c 2011-03-10 08:35:45.532695373 -0800
> +++ b/net/ipv4/tcp_cubic.c 2011-03-10 08:35:59.968882888 -0800
> @@ -88,7 +88,7 @@ struct bictcp {
> u32 last_time; /* time when updated last_cwnd */
> u32 bic_origin_point;/* origin point of bic function */
> u32 bic_K; /* time to origin point from the beginning of the current epoch */
> - u32 delay_min; /* min delay */
> + u32 delay_min; /* min delay (msec << 3) */
> u32 epoch_start; /* beginning of an epoch */
> u32 ack_cnt; /* number of acks */
> u32 tcp_cwnd; /* estimated tcp cwnd */
> @@ -98,7 +98,7 @@ struct bictcp {
> u8 found; /* the exit point is found? */
> u32 round_start; /* beginning of each round */
> u32 end_seq; /* end_seq of the round */
> - u32 last_jiffies; /* last time when the ACK spacing is close */
> + u32 last_ack; /* last time when the ACK spacing is close */
> u32 curr_rtt; /* the minimum rtt of current round */
> };
>
> @@ -119,12 +119,21 @@ static inline void bictcp_reset(struct b
> ca->found = 0;
> }
>
> +static inline u32 bictcp_clock(void)
> +{
> +#if HZ < 1000
> + return ktime_to_ms(ktime_get_real());
> +#else
> + return jiffies_to_ms(jiffies);
> +#endif
> +}
> +
> static inline void bictcp_hystart_reset(struct sock *sk)
> {
> struct tcp_sock *tp = tcp_sk(sk);
> struct bictcp *ca = inet_csk_ca(sk);
>
> - ca->round_start = ca->last_jiffies = jiffies;
> + ca->round_start = ca->last_ack = bictcp_clock();
> ca->end_seq = tp->snd_nxt;
> ca->curr_rtt = 0;
> ca->sample_cnt = 0;
> @@ -239,7 +248,7 @@ static inline void bictcp_update(struct
> */
>
> /* change the unit from HZ to bictcp_HZ */
> - t = ((tcp_time_stamp + (ca->delay_min>>3) - ca->epoch_start)
> + t = ((tcp_time_stamp + msecs_to_jiffies(ca->delay_min>>3) - ca->epoch_start)
> << BICTCP_HZ) / HZ;
>
> if (t < ca->bic_K) /* t - K */
> @@ -342,14 +351,12 @@ static void hystart_update(struct sock *
> struct bictcp *ca = inet_csk_ca(sk);
>
> if (!(ca->found & hystart_detect)) {
> - u32 curr_jiffies = jiffies;
> + u32 now = bictcp_clock();
>
> /* first detection parameter - ack-train detection */
> - if ((s32)(curr_jiffies - ca->last_jiffies) <=
> - msecs_to_jiffies(hystart_ack_delta)) {
> - ca->last_jiffies = curr_jiffies;
> - if ((s32) (curr_jiffies - ca->round_start) <=
> - ca->delay_min >> 4)
> + if ((s32)(now - ca->last_ack) <= hystart_ack_delta) {
> + ca->last_ack = now;
> + if ((s32)(now - ca->round_start) <= ca->delay_min >> 4)
> ca->found |= HYSTART_ACK_TRAIN;
> }
>
> @@ -396,7 +403,7 @@ static void bictcp_acked(struct sock *sk
> if ((s32)(tcp_time_stamp - ca->epoch_start) < HZ)
> return;
>
> - delay = usecs_to_jiffies(rtt_us) << 3;
> + delay = (rtt_us << 3) / USEC_PER_MSEC;
> if (delay == 0)
> delay = 1;
>
>
>
>
--
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