af_unix: reduce high order page allocations (eb6a2481) · Commits · 戴 / test

unix_dgram_sendmsg() currently builds linear skbs, and this can stress page allocator with high order page allocations. When memory gets fragmented, this can eventually fail. We can try to use order-2 allocations for skb head (SKB_MAX_ALLOC) plus up to 16 page fragments to lower pressure on buddy allocator. This patch has no effect on messages of less than 16064 bytes. (on 64bit arches with PAGE_SIZE=4096) For bigger messages (from 16065 to 81600 bytes), this patch brings reliability at the expense of performance penalty because of extra pages allocations. netperf -t DG_STREAM -T 0,2 -- -m 16064 -s 200000 ->4086040 Messages / 10s netperf -t DG_STREAM -T 0,2 -- -m 16068 -s 200000 ->3901747 Messages / 10s Signed-off-by:

Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/unix/af_unix.c

+12 −3

Original line number	Diff line number	Diff line
		@@ -1442,6 +1442,7 @@ static int unix_dgram_sendmsg(struct kiocb kiocb, struct socket sock,
		long timeo;
		struct scm_cookie tmp_scm;
		int max_level;
		int data_len = 0;

		if (NULL == siocb->scm)
		siocb->scm = &tmp_scm;
		@@ -1475,7 +1476,13 @@ static int unix_dgram_sendmsg(struct kiocb kiocb, struct socket sock,
		if (len > sk->sk_sndbuf - 32)
		goto out;

		skb = sock_alloc_send_skb(sk, len, msg->msg_flags&MSG_DONTWAIT, &err);
		if (len > SKB_MAX_ALLOC)
		data_len = min_t(size_t,
		len - SKB_MAX_ALLOC,
		MAX_SKB_FRAGS * PAGE_SIZE);

		skb = sock_alloc_send_pskb(sk, len - data_len, data_len,
		msg->msg_flags & MSG_DONTWAIT, &err);
		if (skb == NULL)
		goto out;

		@@ -1485,8 +1492,10 @@ static int unix_dgram_sendmsg(struct kiocb kiocb, struct socket sock,
		max_level = err + 1;
		unix_get_secdata(siocb->scm, skb);

		skb_reset_transport_header(skb);
		err = memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len);
		skb_put(skb, len - data_len);
		skb->data_len = data_len;
		skb->len = len;
		err = skb_copy_datagram_from_iovec(skb, 0, msg->msg_iov, 0, len);
		if (err)
		goto out_free;

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