On Wed, Jun 09, 2021 at 10:27:48AM +0200, Greg Kroah-Hartman wrote: > 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. And that's what the changelog said, I need more coffee...
