On Thu, Aug 9, 2018 at 10:02 AM Ilias Apalodimas <ilias.apalodi...@linaro.org> wrote: > > MMIO reads for remaining packets in queue occur (at least)twice per > invocation of netsec_process_rx(). We can use the packet descriptor to > identify if it's owned by the hardware and break out, avoiding the more > expensive MMIO read operations. This has a ~2% increase on the pps of the > Rx path when tested with 64byte packets > > Signed-off-by: Ilias Apalodimas <ilias.apalodi...@linaro.org> > --- > drivers/net/ethernet/socionext/netsec.c | 19 +++++-------------- > 1 file changed, 5 insertions(+), 14 deletions(-) > > diff --git a/drivers/net/ethernet/socionext/netsec.c > b/drivers/net/ethernet/socionext/netsec.c > index 01589b6..ae32909 100644 > --- a/drivers/net/ethernet/socionext/netsec.c > +++ b/drivers/net/ethernet/socionext/netsec.c > @@ -657,8 +657,6 @@ static struct sk_buff *netsec_get_rx_pkt_data(struct > netsec_priv *priv,
> + if (de->attr & (1U << NETSEC_RX_PKT_OWN_FIELD)) > + break; > done++; Should this use READ_ONCE() to prevent the compiler from moving the access around? I see that netsec_get_rx_pkt_data() has a dma_rmb() before reading the data, which prevents the CPU from doing something wrong here, but not the compiler. Arnd