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Wed, 02 Dec 2020 14:10:23 -0800 (PST) From: Arjun Roy To: davem@davemloft.net, netdev@vger.kernel.org Cc: arjunroy@google.com, edumazet@google.com, soheil@google.com Subject: [net-next v2 7/8] net-zerocopy: Set zerocopy hint when data is copied Date: Wed, 2 Dec 2020 14:09:44 -0800 Message-Id: <20201202220945.911116-8-arjunroy.kdev@gmail.com> X-Mailer: git-send-email 2.29.2.576.ga3fc446d84-goog In-Reply-To: <20201202220945.911116-1-arjunroy.kdev@gmail.com> References: <20201202220945.911116-1-arjunroy.kdev@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org From: Arjun Roy Set zerocopy hint, event when falling back to copy, so that the pending data can be efficiently received using zerocopy when possible. --- net/ipv4/tcp.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index f67dd732a47b..49480ce162db 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1785,6 +1785,43 @@ static int find_next_mappable_frag(const skb_frag_t *frag, return offset; } +static void tcp_zerocopy_set_hint_for_skb(struct sock *sk, + struct tcp_zerocopy_receive *zc, + struct sk_buff *skb, u32 offset) +{ + u32 frag_offset, partial_frag_remainder = 0; + int mappable_offset; + skb_frag_t *frag; + + /* worst case: skip to next skb. try to improve on this case below */ + zc->recv_skip_hint = skb->len - offset; + + /* Find the frag containing this offset (and how far into that frag) */ + frag = skb_advance_to_frag(skb, offset, &frag_offset); + if (!frag) + return; + + if (frag_offset) { + struct skb_shared_info *info = skb_shinfo(skb); + + /* We read part of the last frag, must recvmsg() rest of skb. */ + if (frag == &info->frags[info->nr_frags - 1]) + return; + + /* Else, we must at least read the remainder in this frag. */ + partial_frag_remainder = skb_frag_size(frag) - frag_offset; + zc->recv_skip_hint -= partial_frag_remainder; + ++frag; + } + + /* partial_frag_remainder: If part way through a frag, must read rest. + * mappable_offset: Bytes till next mappable frag, *not* counting bytes + * in partial_frag_remainder. + */ + mappable_offset = find_next_mappable_frag(frag, zc->recv_skip_hint); + zc->recv_skip_hint = mappable_offset + partial_frag_remainder; +} + static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len, int nonblock, int flags, struct scm_timestamping_internal *tss, @@ -1815,6 +1852,14 @@ static int receive_fallback_to_copy(struct sock *sk, return err; zc->copybuf_len = err; + if (likely(zc->copybuf_len)) { + struct sk_buff *skb; + u32 offset; + + skb = tcp_recv_skb(sk, tcp_sk(sk)->copied_seq, &offset); + if (skb) + tcp_zerocopy_set_hint_for_skb(sk, zc, skb, offset); + } return 0; }