From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Hurley Subject: [PATCH 9/9] n_tty: Avoid false-sharing echo buffer indices Date: Mon, 15 Apr 2013 11:29:47 -0400 Message-ID: <1366039787-8719-10-git-send-email-peter@hurleysoftware.com> References: <1366039567-8620-1-git-send-email-peter@hurleysoftware.com> <1366039787-8719-1-git-send-email-peter@hurleysoftware.com> Return-path: In-Reply-To: <1366039787-8719-1-git-send-email-peter@hurleysoftware.com> Sender: linux-kernel-owner@vger.kernel.org To: Greg Kroah-Hartman Cc: Jiri Slaby , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Hurley List-Id: linux-serial@vger.kernel.org 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 --- 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 eb20777..aa63cd3 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