[065/156] tty: Keep the default buffering to sub-page units
in [Kernel]
|
Prev: [135/156] ipv4: Dont drop redirected route cache entry unless PTMU actually expired
Next: [155/156] GFS2: Skip check for mandatory locks when unlocking
From: Greg KH on 30 Mar 2010 19:30 2.6.33-stable review patch. If anyone has any objections, please let us know. ------------------ From: Alan Cox <alan(a)linux.intel.com> commit d9661adfb8e53a7647360140af3b92284cbe52d4 upstream. We allocate during interrupts so while our buffering is normally diced up small anyway on some hardware at speed we can pressure the VM excessively for page pairs. We don't really need big buffers to be linear so don't try so hard. In order to make this work well we will tidy up excess callers to request_room, which cannot itself enforce this break up. Signed-off-by: Alan Cox <alan(a)linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.de> --- drivers/char/tty_buffer.c | 6 ++++-- include/linux/tty.h | 10 ++++++++++ 2 files changed, 14 insertions(+), 2 deletions(-) --- a/drivers/char/tty_buffer.c +++ b/drivers/char/tty_buffer.c @@ -247,7 +247,8 @@ int tty_insert_flip_string(struct tty_st { int copied = 0; do { - int space = tty_buffer_request_room(tty, size - copied); + int goal = min(size - copied, TTY_BUFFER_PAGE); + int space = tty_buffer_request_room(tty, goal); struct tty_buffer *tb = tty->buf.tail; /* If there is no space then tb may be NULL */ if (unlikely(space == 0)) @@ -283,7 +284,8 @@ int tty_insert_flip_string_flags(struct { int copied = 0; do { - int space = tty_buffer_request_room(tty, size - copied); + int goal = min(size - copied, TTY_BUFFER_PAGE); + int space = tty_buffer_request_room(tty, goal); struct tty_buffer *tb = tty->buf.tail; /* If there is no space then tb may be NULL */ if (unlikely(space == 0)) --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -68,6 +68,16 @@ struct tty_buffer { unsigned long data[0]; }; +/* + * We default to dicing tty buffer allocations to this many characters + * in order to avoid multiple page allocations. We assume tty_buffer itself + * is under 256 bytes. See tty_buffer_find for the allocation logic this + * must match + */ + +#define TTY_BUFFER_PAGE ((PAGE_SIZE - 256) / 2) + + struct tty_bufhead { struct delayed_work work; spinlock_t lock; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |