Commit 7e5ed9f5 authored Dec 13, 2019 by Dmitry Safonov Committed by Greg Kroah-Hartman Dec 17, 2019

serial: Move sysrq members above



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>
Link: https://lore.kernel.org/r/20191213000657.931618-3-dima@arista.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent f06327d1

include/linux/serial_core.h

+6 −5

Original line number	Diff line number	Diff line
		@@ -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];

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