From: Maciej Żenczykowski maze@google.com
commit 1958ff5ad2d4908b44a72bcf564dfe67c981e7fe upstream.
The reasoning for this change is that if we already had a packet pending, then we also already had a pending timer, and as such there is no need to reschedule it.
This also prevents packets getting delayed 60 ms worst case under a tiny packet every 290us transmit load, by keeping the timeout always relative to the first queued up packet. (300us delay * 16KB max aggregation / 80 byte packet =~ 60 ms)
As such the first packet is now at most delayed by 300us.
Under low transmit load, this will simply result in us sending a shorter aggregate, as originally intended.
This patch has the benefit of greatly reducing (by ~10 factor with 1500 byte frames aggregated into 16 kiB) the number of (potentially pretty costly) updates to the hrtimer.
Cc: Brooke Basile brookebasile@gmail.com Cc: Bryan O'Donoghue bryan.odonoghue@linaro.org Cc: Felipe Balbi balbi@kernel.org Cc: Lorenzo Colitti lorenzo@google.com Signed-off-by: Maciej Żenczykowski maze@google.com Link: https://lore.kernel.org/r/20210608085438.813960-1-zenczykowski@gmail.com Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/gadget/function/f_ncm.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
--- a/drivers/usb/gadget/function/f_ncm.c +++ b/drivers/usb/gadget/function/f_ncm.c @@ -1104,11 +1104,11 @@ static struct sk_buff *ncm_wrap_ntb(stru ncm->ndp_dgram_count = 1;
/* Note: we skip opts->next_ndp_index */ - }
- /* Delay the timer. */ - hrtimer_start(&ncm->task_timer, TX_TIMEOUT_NSECS, - HRTIMER_MODE_REL_SOFT); + /* Start the timer. */ + hrtimer_start(&ncm->task_timer, TX_TIMEOUT_NSECS, + HRTIMER_MODE_REL_SOFT); + }
/* Add the datagram position entries */ ntb_ndp = skb_put_zero(ncm->skb_tx_ndp, dgram_idx_len);