| Message ID | Pine.LNX.4.64.0903151041350.23360@wrl-59.cs.helsinki.fi |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On Sun, Mar 15, 2009 at 10:45:16AM +0200, Ilpo Järvinen (ilpo.jarvinen@helsinki.fi) wrote: > > > @@ -676,7 +676,17 @@ static unsigned int tcp_xmit_size_goal(struct sock *sk, u32 mss_now, > > > tp->tcp_header_len); > > > > > > xmit_size_goal = tcp_bound_to_half_wnd(tp, xmit_size_goal); > > > - xmit_size_goal -= (xmit_size_goal % mss_now); > > > + > > > + /* We try hard to avoid divides here */ > > > + old_size_goal = tp->xmit_size_goal_segs * mss_now; > > > + > > > + if (old_size_goal <= xmit_size_goal && > > > + old_size_goal + mss_now > xmit_size_goal) { > > > + xmit_size_goal = old_size_goal; > > > > If this is way more likely condition than changed xmit size, what about > > wrapping it into likely()? > > So gcc won't read my comment? :-) I heared the next gcc version will be linked with the libastral.so, but we have to maintain backward compatibility. > Updated below. The whole series looks good.
From: "Ilpo Järvinen" <ilpo.jarvinen@helsinki.fi> Date: Sun, 15 Mar 2009 10:45:16 +0200 (EET) > [PATCHv2] tcp: cache result of earlier divides when mss-aligning things > > The results is very unlikely change every so often so we > hardly need to divide again after doing that once for a > connection. Yet, if divide still becomes necessary we > detect that and do the right thing and again settle for > non-divide state. Takes the u16 space which was previously > taken by the plain xmit_size_goal. > > This should take care part of the tso vs non-tso difference > we found earlier. > > Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Applied. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/tcp.h b/include/linux/tcp.h index ad2021c..9d5078b 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -248,6 +248,7 @@ struct tcp_sock { /* inet_connection_sock has to be the first member of tcp_sock */ struct inet_connection_sock inet_conn; u16 tcp_header_len; /* Bytes of tcp header to send */ + u16 xmit_size_goal_segs; /* Goal for segmenting output packets */ /* * Header prediction flags diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 886596f..0db9f3b 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -665,7 +665,7 @@ static unsigned int tcp_xmit_size_goal(struct sock *sk, u32 mss_now, int large_allowed) { struct tcp_sock *tp = tcp_sk(sk); - u32 xmit_size_goal; + u32 xmit_size_goal, old_size_goal; xmit_size_goal = mss_now; @@ -676,7 +676,17 @@ static unsigned int tcp_xmit_size_goal(struct sock *sk, u32 mss_now, tp->tcp_header_len); xmit_size_goal = tcp_bound_to_half_wnd(tp, xmit_size_goal); - xmit_size_goal -= (xmit_size_goal % mss_now); + + /* We try hard to avoid divides here */ + old_size_goal = tp->xmit_size_goal_segs * mss_now; + + if (likely(old_size_goal <= xmit_size_goal && + old_size_goal + mss_now > xmit_size_goal)) { + xmit_size_goal = old_size_goal; + } else { + tp->xmit_size_goal_segs = xmit_size_goal / mss_now; + xmit_size_goal = tp->xmit_size_goal_segs * mss_now; + } } return xmit_size_goal;