diff options
| author | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-08-25 17:28:20 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-08-27 11:47:44 +0200 |
| commit | ebf05c7dc92c11b0355aaa0e94064beadaa4b05c (patch) | |
| tree | 09e59c0be773a7a452e1c8ccfca62e35b1da5f38 /include/linux/tty.h | |
| parent | a84853c5954fe2c1b97db2f005ae156dc29ae233 (diff) | |
tty: shrink the size of struct tty_struct by 40 bytes
It's been a long time since anyone has looked at what struct tty_struct
looks like in memory, turns out there was a ton of holes.
So move things around a bit, change one variable (closing) from being an
int to a bool (it is only being tested for 0/1), and we end up saving 40
bytes per structure overall on x86-64 systems.
Before this patch:
/* size: 696, cachelines: 11, members: 37 */
/* sum members: 665, holes: 8, sum holes: 31 */
/* forced alignments: 2, forced holes: 1, sum forced holes: 4 */
/* last cacheline: 56 bytes */
After this change:
/* size: 656, cachelines: 11, members: 37 */
/* sum members: 654, holes: 1, sum holes: 2 */
/* forced alignments: 2 */
/* last cacheline: 16 bytes */
Cc: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/2023082519-cobbler-unholy-8d1f@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux/tty.h')
| -rw-r--r-- | include/linux/tty.h | 18 |
1 files changed, 9 insertions, 9 deletions
diff --git a/include/linux/tty.h b/include/linux/tty.h index e8d5d9997aca..f002d0f25db7 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -192,13 +192,14 @@ struct tty_operations; */ struct tty_struct { struct kref kref; + int index; struct device *dev; struct tty_driver *driver; + struct tty_port *port; const struct tty_operations *ops; - int index; - struct ld_semaphore ldisc_sem; struct tty_ldisc *ldisc; + struct ld_semaphore ldisc_sem; struct mutex atomic_write_lock; struct mutex legacy_mutex; @@ -209,6 +210,7 @@ struct tty_struct { char name[64]; unsigned long flags; int count; + unsigned int receive_room; struct winsize winsize; struct { @@ -219,16 +221,16 @@ struct tty_struct { } __aligned(sizeof(unsigned long)) flow; struct { - spinlock_t lock; struct pid *pgrp; struct pid *session; + spinlock_t lock; unsigned char pktstatus; bool packet; unsigned long unused[0]; } __aligned(sizeof(unsigned long)) ctrl; bool hw_stopped; - unsigned int receive_room; + bool closing; int flow_change; struct tty_struct *link; @@ -239,15 +241,13 @@ struct tty_struct { void *disc_data; void *driver_data; spinlock_t files_lock; + int write_cnt; + unsigned char *write_buf; + struct list_head tty_files; #define N_TTY_BUF_SIZE 4096 - - int closing; - unsigned char *write_buf; - int write_cnt; struct work_struct SAK_work; - struct tty_port *port; } __randomize_layout; /* Each of a tty's open files has private_data pointing to tty_file_private */ |