On 2012-11-14 12:22, Marc Kleine-Budde wrote:
On 11/14/2012 12:02 PM, Andreas Larsson wrote:
On 2012-11-14 09:43, Marc Kleine-Budde wrote:
Handle incoming events (rx or tx-complete) until:
a) number of handled events == budget
or
b) no more events pending.
while (work_done < budget && interrupts_pending()) {
work_done += handle_rx(budget - work_done);
work_done += handle_tx(budget - work_done);
}
That could starve handle_tx completely though under high rx pressure,
but I can prevent that by making sure that half of the budget is held
back in the first call to handle_rx.
What about making the budget big enough to handle both rx and tx in one
napi call. Have a look at the marvell driver [1] for inspiration.
Even if I set the budget to something large, unless I limit the rx side in some
way it could go on multiple rounds around the circular buffer until it have used
all the budget. So in some way or another, grcan_receive must be hindered from
using all the budget.
Sorry, but I am not sure what aspect of the marvell driver poll handling you
want me to mimic. Without having analyzed exactly how the queueing works yet, it
seems to make sure that every function that is called from the poll function
gets ample opportunity to do work by not letting one function hogging all the
budget. If you want me to mimic it in the aspect of doing work in series of 16
or something like that, sure, no problem. If it is something else you want to
point to, please let me know what.
The simplest way to make sure that both tx and rx gets to run is to take
inspiration from the ethoc driver [1] and just let the tx side get just as much
budget as the rx side and be done with it. With the echo frames for can, the
budget should be halved for each I guess to make sure no more frames are
delivered than the budget, but apart from that I don't see the problem with such
a simple approach.
static int ethoc_poll(struct napi_struct *napi, int budget)
{
struct ethoc *priv = container_of(napi, struct ethoc, napi);
int rx_work_done = 0;
int tx_work_done = 0;
rx_work_done = ethoc_rx(priv->netdev, budget);
tx_work_done = ethoc_tx(priv->netdev, budget);
if (rx_work_done < budget && tx_work_done < budget) {
napi_complete(napi);
ethoc_enable_irq(priv, INT_MASK_TX | INT_MASK_RX);
}
return rx_work_done;
}
[1]
http://lxr.free-electrons.com/source/drivers/net/ethernet/ethoc.c#L598
Cheers,
Andreas
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