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SubjectRe: [PATCH tty-next 5/5] tty: Halve flip buffer GFP_ATOMIC memory consumption
On 12/08/2013 08:01 PM, Greg Kroah-Hartman wrote:
> On Fri, Nov 22, 2013 at 12:09:58PM -0500, Peter Hurley wrote:
>> tty flip buffers use GFP_ATOMIC allocations for received data
>> which is to be processed by the line discipline. For each byte
>> received, an extra byte is used to indicate the error status of
>> that byte.
>>
>> Instead, if the received data is error-free, encode the entire
>> buffer without status bytes.
>>
>> Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
>> ---
>> drivers/tty/tty_buffer.c | 45 +++++++++++++++++++++++++++++++++++----------
>> include/linux/tty.h | 4 ++++
>> include/linux/tty_flip.h | 8 ++++++--
>> 3 files changed, 45 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
>> index 6a3620e..c4fe20e 100644
>> --- a/drivers/tty/tty_buffer.c
>> +++ b/drivers/tty/tty_buffer.c
>> @@ -100,6 +100,7 @@ static void tty_buffer_reset(struct tty_buffer *p, size_t size)
>> p->next = NULL;
>> p->commit = 0;
>> p->read = 0;
>> + p->flags = 0;
>> }
>>
>> /**
>> @@ -230,31 +231,49 @@ void tty_buffer_flush(struct tty_struct *tty)
>> * tty_buffer_request_room - grow tty buffer if needed
>> * @tty: tty structure
>> * @size: size desired
>> + * @flags: buffer flags if new buffer allocated (default = 0)
>> *
>> * Make at least size bytes of linear space available for the tty
>> * buffer. If we fail return the size we managed to find.
>> + *
>> + * Will change over to a new buffer if the current buffer is encoded as
>> + * TTY_NORMAL (so has no flags buffer) and the new buffer requires
>> + * a flags buffer.
>> */
>> -int tty_buffer_request_room(struct tty_port *port, size_t size)
>> +int __tty_buffer_request_room(struct tty_port *port, size_t size, int flags)
>> {
>> struct tty_bufhead *buf = &port->buf;
>> struct tty_buffer *b, *n;
>> - int left;
>> + int left, change;
>>
>> b = buf->tail;
>> - left = b->size - b->used;
>> + if (b->flags & TTYB_NORMAL)
>> + left = 2 * b->size - b->used;
>> + else
>> + left = b->size - b->used;
>>
>> - if (left < size) {
>> + change = (b->flags & TTYB_NORMAL) && (~flags & TTYB_NORMAL);
>> + if (change || left < size) {
>> /* This is the slow path - looking for new buffers to use */
>> if ((n = tty_buffer_alloc(port, size)) != NULL) {
>> + n->flags = flags;
>> buf->tail = n;
>> b->commit = b->used;
>> smp_mb();
>> b->next = n;
>> - } else
>> + } else if (change)
>> + size = 0;
>> + else
>> size = left;
>> }
>> return size;
>> }
>> +EXPORT_SYMBOL_GPL(__tty_buffer_request_room);
>
> Why are you exporting this? There is no function prototype anywhere, so
> no one can even try to call it, it should just be static, right?

Yes, sorry. Thanks for catching this.

> I've applied the first 4 patches in this series, care to fix this one
> up?

Patch coming.


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