On Thu, Aug 09, 2018 at 05:37:15PM +0200, Arnd Bergmann wrote: > 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 As we discussed i'll send a V2 with the dma_rmb() right after the desc status read
Thnaks Ilias
