On Tue, Jun 08, 2021 at 01:54:38AM -0700, Maciej Żenczykowski wrote: > From: Maciej Żenczykowski <maze@xxxxxxxxxx> > > 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@xxxxxxxxx> > Cc: Bryan O'Donoghue <bryan.odonoghue@xxxxxxxxxx> > Cc: Felipe Balbi <balbi@xxxxxxxxxx> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Cc: Lorenzo Colitti <lorenzo@xxxxxxxxxx> > Signed-off-by: Maciej Żenczykowski <maze@xxxxxxxxxx> > --- > drivers/usb/gadget/function/f_ncm.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/usb/gadget/function/f_ncm.c b/drivers/usb/gadget/function/f_ncm.c > index 0d23c6c11a13..855127249f24 100644 > --- a/drivers/usb/gadget/function/f_ncm.c > +++ b/drivers/usb/gadget/function/f_ncm.c > @@ -1101,11 +1101,11 @@ static struct sk_buff *ncm_wrap_ntb(struct gether *port, > 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); Nice, hopefully this helps out a lot on the systems where re-arming timers are slow. greg k-h
