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| author | Peter Hurley <peter@hurleysoftware.com> | 2013-11-22 12:09:55 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-12-08 16:57:38 -0800 |
| commit | 4d18e6eff81e1d4d81d0942d5b7e96904b3b32df (patch) | |
| tree | a6c66c84189a50bff8b6b05a7187a8cda4b67cfc | |
| parent | 82f91fe092b6eacd82e976b8955443f9fd97d07e (diff) | |
| download | lwn-4d18e6eff81e1d4d81d0942d5b7e96904b3b32df.tar.gz lwn-4d18e6eff81e1d4d81d0942d5b7e96904b3b32df.zip | |
tty: Enable configurable tty flip buffer limit
Allow driver to configure its maximum flip buffer memory
consumption/limit. This is necessary for very-high speed line
rates (in excess of 10MB/sec) because the flip buffers can
be saturated before the line discipline has a chance to
throttle the input.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/tty_buffer.c | 24 | ||||
| -rw-r--r-- | include/linux/tty.h | 1 | ||||
| -rw-r--r-- | include/linux/tty_flip.h | 1 |
3 files changed, 23 insertions, 3 deletions
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index c043136fbe51..57eb34b2ec24 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -26,7 +26,7 @@ * Byte threshold to limit memory consumption for flip buffers. * The actual memory limit is > 2x this amount. */ -#define TTYB_MEM_LIMIT 65536 +#define TTYB_DEFAULT_MEM_LIMIT 65536 /* * We default to dicing tty buffer allocations to this many characters @@ -89,7 +89,7 @@ void tty_buffer_unlock_exclusive(struct tty_port *port) int tty_buffer_space_avail(struct tty_port *port) { - int space = TTYB_MEM_LIMIT - atomic_read(&port->buf.memory_used); + int space = port->buf.mem_limit - atomic_read(&port->buf.memory_used); return max(space, 0); } @@ -162,7 +162,7 @@ static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size) /* Should possibly check if this fails for the largest buffer we have queued and recycle that ? */ - if (atomic_read(&port->buf.memory_used) > TTYB_MEM_LIMIT) + if (atomic_read(&port->buf.memory_used) > port->buf.mem_limit) return NULL; p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC); if (p == NULL) @@ -536,4 +536,22 @@ void tty_buffer_init(struct tty_port *port) atomic_set(&buf->memory_used, 0); atomic_set(&buf->priority, 0); INIT_WORK(&buf->work, flush_to_ldisc); + buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT; } + +/** + * tty_buffer_set_limit - change the tty buffer memory limit + * @port: tty port to change + * + * Change the tty buffer memory limit. + * Must be called before the other tty buffer functions are used. + */ + +int tty_buffer_set_limit(struct tty_port *port, int limit) +{ + if (limit < MIN_TTYB_SIZE) + return -EINVAL; + port->buf.mem_limit = limit; + return 0; +} +EXPORT_SYMBOL_GPL(tty_buffer_set_limit); diff --git a/include/linux/tty.h b/include/linux/tty.h index 97d660ed70c1..2225745060d6 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -61,6 +61,7 @@ struct tty_bufhead { struct tty_buffer sentinel; struct llist_head free; /* Free queue head */ atomic_t memory_used; /* In-use buffers excluding free list */ + int mem_limit; struct tty_buffer *tail; /* Active buffer */ }; /* diff --git a/include/linux/tty_flip.h b/include/linux/tty_flip.h index 21ddd7d9ea1f..2da8bc2a5486 100644 --- a/include/linux/tty_flip.h +++ b/include/linux/tty_flip.h @@ -1,6 +1,7 @@ #ifndef _LINUX_TTY_FLIP_H #define _LINUX_TTY_FLIP_H +extern int tty_buffer_set_limit(struct tty_port *port, int limit); extern int tty_buffer_space_avail(struct tty_port *port); extern int tty_buffer_request_room(struct tty_port *port, size_t size); extern int tty_insert_flip_string_flags(struct tty_port *port, |