[PATCH 02/58] serial: Move sysrq members above

Dmitry Safonov
2019-12-13T00:07:23Z

At the current place members those follow are:
: upf_t flags;
: upstat_t status;
: int hw_stopped;
: unsigned int mctrl;
: unsigned int timeout;
: unsigned int type;
: const struct uart_ops *ops;

Together, they give (*ops) 8-byte align on 64-bit platforms.
And `sysrq_ch` introduces 4-byte padding.

On the other side, above:
: struct device *dev;
: unsigned char hub6;
: unsigned char suspended;
: unsigned char unused[2];
: const char *name;

Adds another 4-byte padding.

Moving sysrq members just before `hub6` allows to save 8 bytes
per-uart_port on 64-bit platforms:
On my gcc, x86_64 sizeof(struct uart_port) goes from 528 to 520.

Signed-off-by: Dmitry Safonov <dima@arista.com>
---
include/linux/serial_core.h | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 2b78cc734719..bbbe57bf5163 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -161,11 +161,6 @@ struct uart_port {
struct uart_icount icount; /* statistics */

struct console *cons; /* struct console, if any */
-#if defined(CONFIG_SERIAL_CORE_CONSOLE) || defined(SUPPORT_SYSRQ)
- unsigned long sysrq; /* sysrq timeout */
- unsigned int sysrq_ch; /* char for sysrq */
-#endif
-
/* flags must be updated while holding port mutex */
upf_t flags;

@@ -244,6 +239,12 @@ struct uart_port {
resource_size_t mapbase; /* for ioremap */
resource_size_t mapsize;
struct device *dev; /* parent device */
+
+#if defined(CONFIG_SERIAL_CORE_CONSOLE) || defined(SUPPORT_SYSRQ)
+ unsigned long sysrq; /* sysrq timeout */
+ unsigned int sysrq_ch; /* char for sysrq */
+#endif
+
unsigned char hub6; /* this should be in the 8250 driver */
unsigned char suspended;
unsigned char unused[2];
--
2.24.0