* [PATCH net-next] mvpp2: prefetch frame header
@ 2019-10-22 14:14 Matteo Croce
2019-10-24 3:28 ` David Miller
0 siblings, 1 reply; 3+ messages in thread
From: Matteo Croce @ 2019-10-22 14:14 UTC (permalink / raw)
To: netdev
Cc: David S. Miller, Antoine Tenart, Maxime Chevallier,
Marcin Wojtas, Stefan Chulski, linux-kernel
When receiving traffic, eth_type_trans() is high up on the perf top list,
because it's the first function which access the packet data.
Move the DMA unmap a bit higher, and put a prefetch just after it, so we
have more time to load the data into the cache.
The packet rate increase is about 13% with a tc drop test: 1620 => 1830 kpps
Signed-off-by: Matteo Croce <mcroce@redhat.com>
---
drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
index 111b3b8239e1..17378e0d8da1 100644
--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
+++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
@@ -2966,6 +2966,11 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
continue;
}
+ dma_unmap_single(dev->dev.parent, dma_addr,
+ bm_pool->buf_size, DMA_FROM_DEVICE);
+
+ prefetch(data);
+
if (bm_pool->frag_size > PAGE_SIZE)
frag_size = 0;
else
@@ -2983,9 +2988,6 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
goto err_drop_frame;
}
- dma_unmap_single(dev->dev.parent, dma_addr,
- bm_pool->buf_size, DMA_FROM_DEVICE);
-
rcvd_pkts++;
rcvd_bytes += rx_bytes;
--
2.21.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH net-next] mvpp2: prefetch frame header
2019-10-22 14:14 [PATCH net-next] mvpp2: prefetch frame header Matteo Croce
@ 2019-10-24 3:28 ` David Miller
2019-10-24 17:04 ` Matteo Croce
0 siblings, 1 reply; 3+ messages in thread
From: David Miller @ 2019-10-24 3:28 UTC (permalink / raw)
To: mcroce
Cc: netdev, antoine.tenart, maxime.chevallier, mw, stefanc, linux-kernel
From: Matteo Croce <mcroce@redhat.com>
Date: Tue, 22 Oct 2019 16:14:38 +0200
> When receiving traffic, eth_type_trans() is high up on the perf top list,
> because it's the first function which access the packet data.
>
> Move the DMA unmap a bit higher, and put a prefetch just after it, so we
> have more time to load the data into the cache.
>
> The packet rate increase is about 13% with a tc drop test: 1620 => 1830 kpps
>
> Signed-off-by: Matteo Croce <mcroce@redhat.com>
> ---
> drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> index 111b3b8239e1..17378e0d8da1 100644
> --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> @@ -2966,6 +2966,11 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
> continue;
> }
>
> + dma_unmap_single(dev->dev.parent, dma_addr,
> + bm_pool->buf_size, DMA_FROM_DEVICE);
> +
> + prefetch(data);
> +
> if (bm_pool->frag_size > PAGE_SIZE)
> frag_size = 0;
> else
You cannot unmap it this early, because of all of the err_drop_frame
code paths that might be taken next. The DMA mapping must stay in place
in those cases.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH net-next] mvpp2: prefetch frame header
2019-10-24 3:28 ` David Miller
@ 2019-10-24 17:04 ` Matteo Croce
0 siblings, 0 replies; 3+ messages in thread
From: Matteo Croce @ 2019-10-24 17:04 UTC (permalink / raw)
To: David Miller
Cc: netdev, Antoine Tenart, Maxime Chevallier, Marcin Wojtas,
Stefan Chulski, LKML
On Thu, Oct 24, 2019 at 5:28 AM David Miller <davem@davemloft.net> wrote:
> You cannot unmap it this early, because of all of the err_drop_frame
> code paths that might be taken next. The DMA mapping must stay in place
> in those cases.
Thanks for noting this.
I'm sending a series with this and other small fixes.
Regards,
--
Matteo Croce
per aspera ad upstream
^ permalink raw reply [flat|nested] 3+ messages in thread
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