lkml.org 
[lkml]   [2020]   [Mar]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.4 016/155] net: cbs: Fix software cbs to consider packet sending time
    Date
    From: Zh-yuan Ye <ye.zh-yuan@socionext.com>

    [ Upstream commit 961d0e5b32946703125964f9f5b6321d60f4d706 ]

    Currently the software CBS does not consider the packet sending time
    when depleting the credits. It caused the throughput to be
    Idleslope[kbps] * (Port transmit rate[kbps] / |Sendslope[kbps]|) where
    Idleslope * (Port transmit rate / (Idleslope + |Sendslope|)) = Idleslope
    is expected. In order to fix the issue above, this patch takes the time
    when the packet sending completes into account by moving the anchor time
    variable "last" ahead to the send completion time upon transmission and
    adding wait when the next dequeue request comes before the send
    completion time of the previous packet.

    changelog:
    V2->V3:
    - remove unnecessary whitespace cleanup
    - add the checks if port_rate is 0 before division

    V1->V2:
    - combine variable "send_completed" into "last"
    - add the comment for estimate of the packet sending

    Fixes: 585d763af09c ("net/sched: Introduce Credit Based Shaper (CBS) qdisc")
    Signed-off-by: Zh-yuan Ye <ye.zh-yuan@socionext.com>
    Reviewed-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/sched/sch_cbs.c | 12 +++++++++++-
    1 file changed, 11 insertions(+), 1 deletion(-)

    --- a/net/sched/sch_cbs.c
    +++ b/net/sched/sch_cbs.c
    @@ -181,6 +181,11 @@ static struct sk_buff *cbs_dequeue_soft(
    s64 credits;
    int len;

    + /* The previous packet is still being sent */
    + if (now < q->last) {
    + qdisc_watchdog_schedule_ns(&q->watchdog, q->last);
    + return NULL;
    + }
    if (q->credits < 0) {
    credits = timediff_to_credits(now - q->last, q->idleslope);

    @@ -212,7 +217,12 @@ static struct sk_buff *cbs_dequeue_soft(
    credits += q->credits;

    q->credits = max_t(s64, credits, q->locredit);
    - q->last = now;
    + /* Estimate of the transmission of the last byte of the packet in ns */
    + if (unlikely(atomic64_read(&q->port_rate) == 0))
    + q->last = now;
    + else
    + q->last = now + div64_s64(len * NSEC_PER_SEC,
    + atomic64_read(&q->port_rate));

    return skb;
    }

    \
     
     \ /
      Last update: 2020-03-31 11:11    [W:4.142 / U:0.088 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site