* [net-next, PATCH 1/2] net: socionext: Use descriptor info instead of MMIO reads on Rx
@ 2018-08-09 8:02 Ilias Apalodimas
2018-08-09 8:02 ` [net-next, PATCH 2/2] net: socionext: Increase descriptors to 256 Ilias Apalodimas
2018-08-09 15:37 ` [net-next, PATCH 1/2] net: socionext: Use descriptor info instead of MMIO reads on Rx Arnd Bergmann
0 siblings, 2 replies; 4+ messages in thread
From: Ilias Apalodimas @ 2018-08-09 8:02 UTC (permalink / raw)
To: netdev, jaswinder.singh; +Cc: arnd, Ilias Apalodimas
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.apalodimas@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,
/* move tail ahead */
dring->tail = (dring->tail + 1) % DESC_NUM;
- dring->pkt_cnt--;
-
return skb;
}
@@ -731,25 +729,18 @@ static int netsec_process_rx(struct netsec_priv *priv, int budget)
struct netsec_desc_ring *dring = &priv->desc_ring[NETSEC_RING_RX];
struct net_device *ndev = priv->ndev;
struct netsec_rx_pkt_info rx_info;
- int done = 0, rx_num = 0;
+ int done = 0;
struct netsec_desc desc;
struct sk_buff *skb;
u16 len;
while (done < budget) {
- if (!rx_num) {
- rx_num = netsec_read(priv, NETSEC_REG_NRM_RX_PKTCNT);
- dring->pkt_cnt += rx_num;
-
- /* move head 'rx_num' */
- dring->head = (dring->head + rx_num) % DESC_NUM;
+ u16 idx = dring->tail;
+ struct netsec_de *de = dring->vaddr + (DESC_SZ * idx);
- rx_num = dring->pkt_cnt;
- if (!rx_num)
- break;
- }
+ if (de->attr & (1U << NETSEC_RX_PKT_OWN_FIELD))
+ break;
done++;
- rx_num--;
skb = netsec_get_rx_pkt_data(priv, &rx_info, &desc, &len);
if (unlikely(!skb) || rx_info.err_flag) {
netif_err(priv, drv, priv->ndev,
--
2.7.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [net-next, PATCH 2/2] net: socionext: Increase descriptors to 256
2018-08-09 8:02 [net-next, PATCH 1/2] net: socionext: Use descriptor info instead of MMIO reads on Rx Ilias Apalodimas
@ 2018-08-09 8:02 ` Ilias Apalodimas
2018-08-09 15:37 ` [net-next, PATCH 1/2] net: socionext: Use descriptor info instead of MMIO reads on Rx Arnd Bergmann
1 sibling, 0 replies; 4+ messages in thread
From: Ilias Apalodimas @ 2018-08-09 8:02 UTC (permalink / raw)
To: netdev, jaswinder.singh; +Cc: arnd, Ilias Apalodimas
Increasing descriptors to 256 from 128 and adjusting the NAPI weight
to 64 increases performace on Rx by ~20% on 64byte packets
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
---
drivers/net/ethernet/socionext/netsec.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/socionext/netsec.c b/drivers/net/ethernet/socionext/netsec.c
index ae32909..5d2007b 100644
--- a/drivers/net/ethernet/socionext/netsec.c
+++ b/drivers/net/ethernet/socionext/netsec.c
@@ -232,8 +232,7 @@
#define NETSEC_EEPROM_PKT_ME_ADDRESS 0x20
#define NETSEC_EEPROM_PKT_ME_SIZE 0x24
-#define DESC_NUM 128
-#define NAPI_BUDGET (DESC_NUM / 2)
+#define DESC_NUM 256
#define DESC_SZ sizeof(struct netsec_de)
@@ -1655,7 +1654,7 @@ static int netsec_probe(struct platform_device *pdev)
dev_info(&pdev->dev, "hardware revision %d.%d\n",
hw_ver >> 16, hw_ver & 0xffff);
- netif_napi_add(ndev, &priv->napi, netsec_napi_poll, NAPI_BUDGET);
+ netif_napi_add(ndev, &priv->napi, netsec_napi_poll, NAPI_POLL_WEIGHT);
ndev->netdev_ops = &netsec_netdev_ops;
ndev->ethtool_ops = &netsec_ethtool_ops;
--
2.7.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [net-next, PATCH 1/2] net: socionext: Use descriptor info instead of MMIO reads on Rx
2018-08-09 8:02 [net-next, PATCH 1/2] net: socionext: Use descriptor info instead of MMIO reads on Rx Ilias Apalodimas
2018-08-09 8:02 ` [net-next, PATCH 2/2] net: socionext: Increase descriptors to 256 Ilias Apalodimas
@ 2018-08-09 15:37 ` Arnd Bergmann
2018-08-09 19:05 ` Ilias Apalodimas
1 sibling, 1 reply; 4+ messages in thread
From: Arnd Bergmann @ 2018-08-09 15:37 UTC (permalink / raw)
To: Ilias Apalodimas; +Cc: Networking, Jassi Brar
On Thu, Aug 9, 2018 at 10:02 AM Ilias Apalodimas
<ilias.apalodimas@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.apalodimas@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
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [net-next, PATCH 1/2] net: socionext: Use descriptor info instead of MMIO reads on Rx
2018-08-09 15:37 ` [net-next, PATCH 1/2] net: socionext: Use descriptor info instead of MMIO reads on Rx Arnd Bergmann
@ 2018-08-09 19:05 ` Ilias Apalodimas
0 siblings, 0 replies; 4+ messages in thread
From: Ilias Apalodimas @ 2018-08-09 19:05 UTC (permalink / raw)
To: Arnd Bergmann; +Cc: Networking, Jassi Brar
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.apalodimas@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.apalodimas@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
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2018-08-09 21:31 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2018-08-09 8:02 [net-next, PATCH 1/2] net: socionext: Use descriptor info instead of MMIO reads on Rx Ilias Apalodimas
2018-08-09 8:02 ` [net-next, PATCH 2/2] net: socionext: Increase descriptors to 256 Ilias Apalodimas
2018-08-09 15:37 ` [net-next, PATCH 1/2] net: socionext: Use descriptor info instead of MMIO reads on Rx Arnd Bergmann
2018-08-09 19:05 ` Ilias Apalodimas
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