From 9dfd16ddea9bdbc8343340e543732db0a467ae32 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Sat, 15 Jun 2013 10:04:29 -0400 Subject: [PATCH] n_tty: Avoid false-sharing echo buffer indices 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 Signed-off-by: Greg Kroah-Hartman --- 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 7f15b269cf3e..d4d71350a71d 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; -- 2.20.1