[PATCH v2 9/9] n_tty: Avoid false-sharing echo buffer indices
From: Peter Hurley <hidden>
Date: 2013-06-15 14:05:44
Also in:
lkml
Subsystem:
the rest, tty layer and serial drivers · Maintainers:
Linus Torvalds, Greg Kroah-Hartman, Jiri Slaby
Separate the head & commit indices from the tail index to avoid cache-line contention (so called 'false-sharing') between concurrent threads. Signed-off-by: Peter Hurley <redacted> --- drivers/tty/n_tty.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index e689026..b9ccb49 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c@@ -90,6 +90,8 @@ struct n_tty_data { /* producer-published */ size_t read_head; size_t canon_head; + size_t echo_head; + size_t echo_commit; DECLARE_BITMAP(process_char_map, 256); /* private to n_tty_receive_overrun (single-threaded) */
@@ -105,20 +107,17 @@ struct n_tty_data { /* shared by producer and consumer */ char *read_buf; DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE); + unsigned char *echo_buf; int minimum_to_wake; /* consumer-published */ size_t read_tail; - unsigned char *echo_buf; - size_t echo_head; - size_t echo_tail; - size_t echo_commit; - /* protected by output lock */ unsigned int column; unsigned int canon_column; + size_t echo_tail; struct mutex atomic_read_lock; struct mutex output_lock;
--
1.8.1.2