From cdda911c34006f1089f3c87b1a1f31ab3a4722f2 Mon Sep 17 00:00:00 2001 From: Jeff Brown Date: Tue, 26 Apr 2011 22:16:11 -0700 Subject: Input: evdev - only signal polls on full packets This patch modifies evdev so that it only becomes readable when the buffer contains an EV_SYN/SYN_REPORT event. On SMP systems, it is possible for an evdev client blocked on poll() to wake up and read events from the evdev ring buffer at the same rate as they are enqueued. This can result in high CPU usage, particularly for MT devices, because the client ends up reading events one at a time instead of reading complete packets. We eliminate this problem by making the device readable only when the buffer contains at least one complete packet. This causes clients to block until the entire packet is available. Signed-off-by: Jeff Brown Signed-off-by: Dmitry Torokhov --- drivers/input/evdev.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) (limited to 'drivers/input/evdev.c') diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c index 88d8e4cb419..75c4e868303 100644 --- a/drivers/input/evdev.c +++ b/drivers/input/evdev.c @@ -41,6 +41,7 @@ struct evdev { struct evdev_client { unsigned int head; unsigned int tail; + unsigned int packet_head; /* [future] position of the first element of next packet */ spinlock_t buffer_lock; /* protects access to buffer, head and tail */ struct fasync_struct *fasync; struct evdev *evdev; @@ -72,12 +73,16 @@ static void evdev_pass_event(struct evdev_client *client, client->buffer[client->tail].type = EV_SYN; client->buffer[client->tail].code = SYN_DROPPED; client->buffer[client->tail].value = 0; - } - spin_unlock(&client->buffer_lock); + client->packet_head = client->tail; + } - if (event->type == EV_SYN) + if (event->type == EV_SYN && event->code == SYN_REPORT) { + client->packet_head = client->head; kill_fasync(&client->fasync, SIGIO, POLL_IN); + } + + spin_unlock(&client->buffer_lock); } /* @@ -387,12 +392,12 @@ static ssize_t evdev_read(struct file *file, char __user *buffer, if (count < input_event_size()) return -EINVAL; - if (client->head == client->tail && evdev->exist && + if (client->packet_head == client->tail && evdev->exist && (file->f_flags & O_NONBLOCK)) return -EAGAIN; retval = wait_event_interruptible(evdev->wait, - client->head != client->tail || !evdev->exist); + client->packet_head != client->tail || !evdev->exist); if (retval) return retval; @@ -421,7 +426,7 @@ static unsigned int evdev_poll(struct file *file, poll_table *wait) poll_wait(file, &evdev->wait, wait); mask = evdev->exist ? POLLOUT | POLLWRNORM : POLLHUP | POLLERR; - if (client->head != client->tail) + if (client->packet_head != client->tail) mask |= POLLIN | POLLRDNORM; return mask; -- cgit v1.2.3-70-g09d2 From 7cbbb758d3c93b24b45b169af55440d2e7d5b7f6 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 11 May 2011 15:38:10 -0700 Subject: Input: remove useless synchronize_rcu() calls There is no need to call synchronize_rcu() after a list insertion, or a NULL->ptr assignment. However, the reverse operations do need this call. Signed-off-by: Eric Dumazet Signed-off-by: Dmitry Torokhov --- drivers/input/evdev.c | 2 -- drivers/input/input.c | 1 - drivers/input/joydev.c | 1 - drivers/input/mousedev.c | 1 - 4 files changed, 5 deletions(-) (limited to 'drivers/input/evdev.c') diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c index 75c4e868303..be0921ef6b5 100644 --- a/drivers/input/evdev.c +++ b/drivers/input/evdev.c @@ -164,7 +164,6 @@ static int evdev_grab(struct evdev *evdev, struct evdev_client *client) return error; rcu_assign_pointer(evdev->grab, client); - synchronize_rcu(); return 0; } @@ -187,7 +186,6 @@ static void evdev_attach_client(struct evdev *evdev, spin_lock(&evdev->client_lock); list_add_tail_rcu(&client->node, &evdev->client_list); spin_unlock(&evdev->client_lock); - synchronize_rcu(); } static void evdev_detach_client(struct evdev *evdev, diff --git a/drivers/input/input.c b/drivers/input/input.c index ebbceedc92f..75e11c7b70f 100644 --- a/drivers/input/input.c +++ b/drivers/input/input.c @@ -451,7 +451,6 @@ int input_grab_device(struct input_handle *handle) } rcu_assign_pointer(dev->grab, handle); - synchronize_rcu(); out: mutex_unlock(&dev->mutex); diff --git a/drivers/input/joydev.c b/drivers/input/joydev.c index 5688b5c88f2..c24ec2d5f92 100644 --- a/drivers/input/joydev.c +++ b/drivers/input/joydev.c @@ -180,7 +180,6 @@ static void joydev_attach_client(struct joydev *joydev, spin_lock(&joydev->client_lock); list_add_tail_rcu(&client->node, &joydev->client_list); spin_unlock(&joydev->client_lock); - synchronize_rcu(); } static void joydev_detach_client(struct joydev *joydev, diff --git a/drivers/input/mousedev.c b/drivers/input/mousedev.c index 7630273e947..257e033986e 100644 --- a/drivers/input/mousedev.c +++ b/drivers/input/mousedev.c @@ -508,7 +508,6 @@ static void mousedev_attach_client(struct mousedev *mousedev, spin_lock(&mousedev->client_lock); list_add_tail_rcu(&client->node, &mousedev->client_list); spin_unlock(&mousedev->client_lock); - synchronize_rcu(); } static void mousedev_detach_client(struct mousedev *mousedev, -- cgit v1.2.3-70-g09d2