[PATCH net-next] tcp: shrink inet_connection_sock icsk_mtup enabled and probe_size

[PATCH net-next] tcp: shrink inet_connection_sock icsk_mtup enabled and probe_size

[Neal Cardwell]

From: Neal Cardwell <ncardwell@google.com>

This commit shrinks inet_connection_sock by 4 bytes, by shrinking
icsk_mtup.enabled from 32 bits to 1 bit, and shrinking
icsk_mtup.probe_size from s32 to an unsuigned 31 bit field.

This is to save space to compensate for the recent introduction of a
new u32 in inet_connection_sock, icsk_probes_tstamp, in the recent bug
fix commit 9d9b1ee0b2d1 ("tcp: fix TCP_USER_TIMEOUT with zero window").

This should not change functionality, since icsk_mtup.enabled is only
ever set to 0 or 1, and icsk_mtup.probe_size can only be either 0
or a positive MTU value returned by tcp_mss_to_mtu()

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/inet_connection_sock.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index c11f80f328f1..10a625760de9 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -120,14 +120,14 @@ struct inet_connection_sock {
 		__u16		  rcv_mss;	 /* MSS used for delayed ACK decisions	   */
 	} icsk_ack;
 	struct {
-		int		  enabled;
-
 		/* Range of MTUs to search */
 		int		  search_high;
 		int		  search_low;
 
 		/* Information on the current probe. */
-		int		  probe_size;
+		u32		  probe_size:31,
+		/* Is the MTUP feature enabled for this connection? */
+				  enabled:1;
 
 		u32		  probe_timestamp;
 	} icsk_mtup;
-- 
2.30.0.365.g02bc693789-goog

Re: [PATCH net-next] tcp: shrink inet_connection_sock icsk_mtup enabled and probe_size

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Fri, 29 Jan 2021 13:54:38 -0500 you wrote:
> From: Neal Cardwell <ncardwell@google.com>
> 
> This commit shrinks inet_connection_sock by 4 bytes, by shrinking
> icsk_mtup.enabled from 32 bits to 1 bit, and shrinking
> icsk_mtup.probe_size from s32 to an unsuigned 31 bit field.
> 
> This is to save space to compensate for the recent introduction of a
> new u32 in inet_connection_sock, icsk_probes_tstamp, in the recent bug
> fix commit 9d9b1ee0b2d1 ("tcp: fix TCP_USER_TIMEOUT with zero window").
> 
> [...]

Here is the summary with links:
  - [net-next] tcp: shrink inet_connection_sock icsk_mtup enabled and probe_size
    https://git.kernel.org/netdev/net-next/c/14e8e0f60088

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html