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From: John Fastabend <john.fastabend@gmail.com>
To: john.fastabend@gmail.com, alexei.starovoitov@gmail.com,
	daniel@iogearbox.net
Cc: netdev@vger.kernel.org, bpf@vger.kernel.org,
	jakub@cloudflare.com, lmb@cloudflare.com
Subject: [bpf-next PATCH v3 3/6] bpf, sockmap: remove skb_set_owner_w wmem will be taken later from sendpage
Date: Fri, 09 Oct 2020 11:36:57 -0700	[thread overview]
Message-ID: <160226861708.5692.17964237936462425136.stgit@john-Precision-5820-Tower> (raw)
In-Reply-To: <160226839426.5692.13107801574043388675.stgit@john-Precision-5820-Tower>

The skb_set_owner_w is unnecessary here. The sendpage call will create a
fresh skb and set the owner correctly from workqueue. Its also not entirely
harmless because it consumes cycles, but also impacts resource accounting
by increasing sk_wmem_alloc. This is charging the socket we are going to
send to for the skb, but we will put it on the workqueue for some time
before this happens so we are artifically inflating sk_wmem_alloc for
this period. Further, we don't know how many skbs will be used to send the
packet or how it will be broken up when sent over the new socket so
charging it with one big sum is also not correct when the workqueue may
break it up if facing memory pressure. Seeing we don't know how/when
this is going to be sent drop the early accounting.

A later patch will do proper accounting charged on receive socket for
the case where skbs get enqueued on the workqueue.

Fixes: 604326b41a6fb ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
---
 net/core/skmsg.c |    2 --
 1 file changed, 2 deletions(-)

diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 4b160d97b7f9..7389d5d7e7f8 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -728,8 +728,6 @@ static void sk_psock_skb_redirect(struct sk_buff *skb)
 	    (ingress &&
 	     atomic_read(&sk_other->sk_rmem_alloc) <=
 	     sk_other->sk_rcvbuf)) {
-		if (!ingress)
-			skb_set_owner_w(skb, sk_other);
 		skb_queue_tail(&psock_other->ingress_skb, skb);
 		schedule_work(&psock_other->work);
 	} else {


  parent reply	other threads:[~2020-10-09 18:37 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-09 18:35 [bpf-next PATCH v2 0/6] sockmap/sk_skb program memory acct fixes John Fastabend
2020-10-09 18:36 ` [bpf-next PATCH v3 1/6] bpf, sockmap: skb verdict SK_PASS to self already checked rmem limits John Fastabend
2020-10-09 18:36 ` [bpf-next PATCH v3 2/6] bpf, sockmap: On receive programs try to fast track SK_PASS ingress John Fastabend
2020-10-12  9:03   ` Jakub Sitnicki
2020-10-12 15:33     ` John Fastabend
2020-10-13 19:43       ` Jakub Sitnicki
2020-10-09 18:36 ` John Fastabend [this message]
2020-10-09 18:37 ` [bpf-next PATCH v3 4/6] bpf, sockmap: remove dropped data on errors in redirect case John Fastabend
2020-10-12 12:04   ` Jakub Sitnicki
2020-10-12 17:19     ` John Fastabend
2020-10-13 10:27       ` Jakub Sitnicki
2020-10-09 18:37 ` [bpf-next PATCH v3 5/6] bpf, sockmap: Remove skb_orphan and let normal skb_kfree do cleanup John Fastabend
2020-10-09 18:37 ` [bpf-next PATCH v3 6/6] bpf, sockmap: Add memory accounting so skbs on ingress lists are visible John Fastabend
2020-10-12  1:10 ` [bpf-next PATCH v2 0/6] sockmap/sk_skb program memory acct fixes patchwork-bot+netdevbpf

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