linux-kernel - [PATCH net-next v2 3/3] mvpp2: prefetch frame header

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Message-Id: <20191024172458.7956-4-mcroce@redhat.com>
Date:   Thu, 24 Oct 2019 19:24:58 +0200
From:   Matteo Croce <mcroce@...hat.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Antoine Tenart <antoine.tenart@...tlin.com>,
        Maxime Chevallier <maxime.chevallier@...tlin.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        Stefan Chulski <stefanc@...vell.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH net-next v2 3/3] mvpp2: prefetch frame header

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 14% with a tc drop test: 1620 => 1853 kpps

Signed-off-by: Matteo Croce <mcroce@...hat.com>
---
 drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
index 15818e1d6b04..a55de943d5cb 100644
--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
+++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
@@ -2963,6 +2963,7 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
 		dma_sync_single_for_cpu(dev->dev.parent, dma_addr,
 					rx_bytes + MVPP2_MH_SIZE,
 					DMA_FROM_DEVICE);
+		prefetch(data);
 
 		if (bm_pool->frag_size > PAGE_SIZE)
 			frag_size = 0;
-- 
2.21.0