From: Chia-Yu Chang <[email protected]>
Use the first 3-byte hole at the beginning of the tcp_sock_write_txrx
group for 'noneagle'/'rate_app_limited' to fill in the exisintg hole
in later patches. Below are the trimmed pahole outcomes before and after
this patch.
[BEFORE THIS PATCH]
struct tcp_sock {
[...]
__cacheline_group_begin__tcp_sock_write_txrx[0]; /* 2585 0 */
/* XXX 3 bytes hole, try to pack */
[...]
struct tcp_options_received rx_opt; /* 2652 24 */
u8 nonagle:4; /* 2676: 0 1 */
u8 rate_app_limited:1; /* 2676: 4 1 */
/* XXX 3 bits hole, try to pack */
__cacheline_group_end__tcp_sock_write_txrx[0]; /* 2677 0 */
/* XXX 3 bytes hole, try to pack */
[...]
/* size: 3264, cachelines: 51, members: 163 */
}
[AFTER THIS PATCH]
struct tcp_sock {
[...]
__cacheline_group_begin__tcp_sock_write_txrx[0]; /* 2585 0 */
u8 nonagle:4; /* 2585: 0 1 */
u8 rate_app_limited:1; /* 2585: 4 1 */
/* XXX 3 bits hole, try to pack */
/* XXX 2 bytes hole, try to pack */
[...]
struct tcp_options_received rx_opt; /* 2652 24 */
__cacheline_group_end__tcp_sock_write_txrx[0]; /* 2676 0 */
/* XXX 4 bytes hole, try to pack */
[...]
/* size: 3264, cachelines: 51, members: 163 */
}
Signed-off-by: Chia-Yu Chang <[email protected]>
---
include/linux/tcp.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index a8af71623ba7..0c82a8c942dc 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -286,6 +286,8 @@ struct tcp_sock {
* Header prediction flags
* 0x5?10 << 16 + snd_wnd in net byte order
*/
+ u8 nonagle : 4,/* Disable Nagle algorithm? */
+ rate_app_limited:1; /* rate_{delivered,interval_us} limited? */
__be32 pred_flags;
u64 tcp_clock_cache; /* cache last tcp_clock_ns() (see
tcp_mstamp_refresh()) */
u64 tcp_mstamp; /* most recent packet received/sent */
@@ -304,8 +306,6 @@ struct tcp_sock {
* Options received (usually on last packet, some only on SYN packets).
*/
struct tcp_options_received rx_opt;
- u8 nonagle : 4,/* Disable Nagle algorithm? */
- rate_app_limited:1; /* rate_{delivered,interval_us} limited? */
__cacheline_group_end(tcp_sock_write_txrx);
/* RX read-write hotpath cache lines */
--
2.34.1
