From d62fda082c48b417b47a553860abf75d9cf8b591 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 12 May 2009 20:48:02 +0000 Subject: bnx2: bnx2_tx_int() optimizations When using bnx2 in a high transmit load, bnx2_tx_int() cost is pretty high. There are two reasons. One is an expensive call to bnx2_get_hw_tx_cons(bnapi) for each freed skb One is cpu stalls when accessing skb_is_gso(skb) / skb_shinfo(skb)->nr_frags because of two cache line misses. (One to get skb->end/head to compute skb_shinfo(skb), one to get is_gso/nr_frags) This patch : 1) avoids calling bnx2_get_hw_tx_cons(bnapi) too many times. 2) makes bnx2_start_xmit() cache is_gso & nr_frags into sw_tx_bd descriptor. This uses a litle bit more ram (256 longs per device on x86), but helps a lot. 3) uses a prefetch(&skb->end) to speedup dev_kfree_skb(), bringing cache line that will be needed in skb_release_data() result is 5 % bandwidth increase in benchmarks, involving UDP or TCP receive & transmits, when a cpu is dedicated to ksoftirqd for bnx2. bnx2_tx_int going from 3.33 % cpu to 0.5 % cpu in oprofile Note : skb_dma_unmap() still very expensive but this is for another patch, not related to bnx2 (2.9 % of cpu, while it does nothing on x86_32) Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- drivers/net/bnx2.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) (limited to 'drivers/net/bnx2.c') diff --git a/drivers/net/bnx2.c b/drivers/net/bnx2.c index b0cb29d4cc01..c37acc1d10ac 100644 --- a/drivers/net/bnx2.c +++ b/drivers/net/bnx2.c @@ -2630,14 +2630,15 @@ bnx2_tx_int(struct bnx2 *bp, struct bnx2_napi *bnapi, int budget) tx_buf = &txr->tx_buf_ring[sw_ring_cons]; skb = tx_buf->skb; + /* prefetch skb_end_pointer() to speedup skb_shinfo(skb) */ + prefetch(&skb->end); + /* partial BD completions possible with TSO packets */ - if (skb_is_gso(skb)) { + if (tx_buf->is_gso) { u16 last_idx, last_ring_idx; - last_idx = sw_cons + - skb_shinfo(skb)->nr_frags + 1; - last_ring_idx = sw_ring_cons + - skb_shinfo(skb)->nr_frags + 1; + last_idx = sw_cons + tx_buf->nr_frags + 1; + last_ring_idx = sw_ring_cons + tx_buf->nr_frags + 1; if (unlikely(last_ring_idx >= MAX_TX_DESC_CNT)) { last_idx++; } @@ -2649,7 +2650,7 @@ bnx2_tx_int(struct bnx2 *bp, struct bnx2_napi *bnapi, int budget) skb_dma_unmap(&bp->pdev->dev, skb, DMA_TO_DEVICE); tx_buf->skb = NULL; - last = skb_shinfo(skb)->nr_frags; + last = tx_buf->nr_frags; for (i = 0; i < last; i++) { sw_cons = NEXT_TX_BD(sw_cons); @@ -2662,7 +2663,8 @@ bnx2_tx_int(struct bnx2 *bp, struct bnx2_napi *bnapi, int budget) if (tx_pkt == budget) break; - hw_cons = bnx2_get_hw_tx_cons(bnapi); + if (hw_cons == sw_cons) + hw_cons = bnx2_get_hw_tx_cons(bnapi); } txr->hw_tx_cons = hw_cons; @@ -6179,6 +6181,8 @@ bnx2_start_xmit(struct sk_buff *skb, struct net_device *dev) txbd->tx_bd_vlan_tag_flags = vlan_tag_flags | TX_BD_FLAGS_START; last_frag = skb_shinfo(skb)->nr_frags; + tx_buf->nr_frags = last_frag; + tx_buf->is_gso = skb_is_gso(skb); for (i = 0; i < last_frag; i++) { skb_frag_t *frag = &skb_shinfo(skb)->frags[i]; -- cgit v1.2.2