netdev - [PATCH bpf-next] xsk: add test for tx

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Date:   Tue, 14 Dec 2021 11:26:47 +0100
From:   Magnus Karlsson <magnus.karlsson@...il.com>
To:     magnus.karlsson@...el.com, bjorn@...nel.org, ast@...nel.org,
        daniel@...earbox.net, netdev@...r.kernel.org,
        maciej.fijalkowski@...el.com
Cc:     jonathan.lemon@...il.com, bpf@...r.kernel.org
Subject: [PATCH bpf-next] xsk: add test for tx_writeable to batched path

From: Magnus Karlsson <magnus.karlsson@...el.com>

Add a test for the tx_writeable condition to the batched Tx processing
path. This test is in the skb and non-batched code paths but not in the
batched code path. So add it there. This test makes sure that a
process is not woken up until there are a sufficiently large number of
free entries in the Tx ring. Currently, any driver using the batched
interface will be woken up even if there is only one free entry,
impacting performance negatively.

Fixes: 3413f04141aa ("xsk: Change the tx writeable condition")
Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
---
 net/xdp/xsk.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 28ef3f4465ae..3772fcaa76ed 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -392,7 +392,8 @@ u32 xsk_tx_peek_release_desc_batch(struct xsk_buff_pool *pool, struct xdp_desc *
 
 	xskq_cons_release_n(xs->tx, nb_pkts);
 	__xskq_cons_release(xs->tx);
-	xs->sk.sk_write_space(&xs->sk);
+	if (xsk_tx_writeable(xs))
+		xs->sk.sk_write_space(&xs->sk);
 
 out:
 	rcu_read_unlock();

base-commit: d27a662290963a1cde26cdfdbac71a546c06e94a
-- 
2.29.0