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Commit e60d27c4 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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n_tty: Factor LNEXT processing from per-char i/o path 



LNEXT processing accounts for ~15% of total cpu time in end-to-end
tty i/o; factor the lnext test/clear from the per-char i/o path.

Instead, attempt to immediately handle the literal next char if not
at the end of this received buffer; otherwise, handle the first char
of the next received buffer as the literal next char, then continue
with normal i/o.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 4b293492

drivers/tty/n_tty.c

+94 −72
Original line number Diff line number Diff line
@@ -1249,9 +1249,11 @@ n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c) 
 *		caller holds non-exclusive termios_rwsem

 *		publishes canon_head if canonical mode is active

 *		otherwise, publishes read_head via put_tty_queue()

 *

 *	Returns 1 if LNEXT was received, else returns 0

 */



static void

static int

n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)

{

	struct n_tty_data *ldata = tty->disc_data;
@@ -1261,24 +1263,24 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c) 
		if (c == START_CHAR(tty)) {

			start_tty(tty);

			commit_echoes(tty);

			return;

			return 0;

		}

		if (c == STOP_CHAR(tty)) {

			stop_tty(tty);

			return;

			return 0;

		}

	}



	if (L_ISIG(tty)) {

		if (c == INTR_CHAR(tty)) {

			n_tty_receive_signal_char(tty, SIGINT, c);

			return;

			return 0;

		} else if (c == QUIT_CHAR(tty)) {

			n_tty_receive_signal_char(tty, SIGQUIT, c);

			return;

			return 0;

		} else if (c == SUSP_CHAR(tty)) {

			n_tty_receive_signal_char(tty, SIGTSTP, c);

			return;

			return 0;

		}

	}
@@ -1289,7 +1291,7 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c) 


	if (c == '\r') {

		if (I_IGNCR(tty))

			return;

			return 0;

		if (I_ICRNL(tty))

			c = '\n';

	} else if (c == '\n' && I_INLCR(tty))
@@ -1300,7 +1302,7 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c) 
		    (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {

			eraser(c, tty);

			commit_echoes(tty);

			return;

			return 0;

		}

		if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {

			ldata->lnext = 1;
@@ -1312,10 +1314,9 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c) 
					commit_echoes(tty);

				}

			}

			return;

			return 1;

		}

		if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&

		    L_IEXTEN(tty)) {

		if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {

			size_t tail = ldata->canon_head;



			finish_erasing(ldata);
@@ -1326,7 +1327,7 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c) 
				tail++;

			}

			commit_echoes(tty);

			return;

			return 0;

		}

		if (c == '\n') {

			if (L_ECHO(tty) || L_ECHONL(tty)) {
@@ -1367,7 +1368,7 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c) 
			kill_fasync(&tty->fasync, SIGIO, POLL_IN);

			if (waitqueue_active(&tty->read_wait))

				wake_up_interruptible(&tty->read_wait);

			return;

			return 0;

		}

	}
@@ -1389,24 +1390,16 @@ n_tty_receive_char_special(struct tty_struct *tty, unsigned char c) 
		put_tty_queue(c, ldata);



	put_tty_queue(c, ldata);

	return 0;

}



static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)

static inline void

n_tty_receive_char_inline(struct tty_struct *tty, unsigned char c)

{

	struct n_tty_data *ldata = tty->disc_data;

	int parmrk;



	/*

	 * If the previous character was LNEXT, or we know that this

	 * character is not one of the characters that we'll have to

	 * handle specially, do shortcut processing to speed things

	 * up.

	 */

	if (!test_bit(c, ldata->char_map) || ldata->lnext) {

		ldata->lnext = 0;



		if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&

		    I_IXANY(tty)) {

	if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {

		start_tty(tty);

		process_echoes(tty);

	}
@@ -1422,10 +1415,11 @@ static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c) 
	if (parmrk)

		put_tty_queue(c, ldata);

	put_tty_queue(c, ldata);

		return;

}



	n_tty_receive_char_special(tty, c);

static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)

{

	n_tty_receive_char_inline(tty, c);

}



static inline void
@@ -1433,17 +1427,7 @@ n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c) 
{

	struct n_tty_data *ldata = tty->disc_data;



	/*

	 * If the previous character was LNEXT, or we know that this

	 * character is not one of the characters that we'll have to

	 * handle specially, do shortcut processing to speed things

	 * up.

	 */

	if (!test_bit(c, ldata->char_map) || ldata->lnext) {

		ldata->lnext = 0;



		if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&

		    I_IXANY(tty)) {

	if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {

		start_tty(tty);

		process_echoes(tty);

	}
@@ -1456,10 +1440,6 @@ n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c) 
		commit_echoes(tty);

	}

	put_tty_queue(c, ldata);

		return;

	}



	n_tty_receive_char_special(tty, c);

}



static inline void
@@ -1506,6 +1486,22 @@ n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag) 
	}

}



static void

n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)

{

	struct n_tty_data *ldata = tty->disc_data;



	ldata->lnext = 0;

	if (likely(flag == TTY_NORMAL)) {

		if (I_ISTRIP(tty))

			c &= 0x7f;

		if (I_IUCLC(tty) && L_IEXTEN(tty))

			c = tolower(c);

		n_tty_receive_char(tty, c);

	} else

		n_tty_receive_char_flagged(tty, c, flag);

}



/**

 *	n_tty_receive_buf	-	data receive

 *	@tty: terminal device
@@ -1599,7 +1595,14 @@ n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp, 
				put_tty_queue(c, ldata);

				continue;

			}

			n_tty_receive_char(tty, c);

			if (!test_bit(c, ldata->char_map))

				n_tty_receive_char_inline(tty, c);

			else if (n_tty_receive_char_special(tty, c) && count) {

				if (fp)

					flag = *fp++;

				n_tty_receive_char_lnext(tty, *cp++, flag);

				count--;

			}

		} else

			n_tty_receive_char_flagged(tty, *cp++, flag);

	}
@@ -1609,14 +1612,24 @@ static void 
n_tty_receive_buf_fast(struct tty_struct *tty, const unsigned char *cp,

		       char *fp, int count)

{

	struct n_tty_data *ldata = tty->disc_data;

	char flag = TTY_NORMAL;



	while (count--) {

		if (fp)

			flag = *fp++;

		if (likely(flag == TTY_NORMAL))

			n_tty_receive_char_fast(tty, *cp++);

		else

		if (likely(flag == TTY_NORMAL)) {

			unsigned char c = *cp++;



			if (!test_bit(c, ldata->char_map))

				n_tty_receive_char_fast(tty, c);

			else if (n_tty_receive_char_special(tty, c) && count) {

				if (fp)

					flag = *fp++;

				n_tty_receive_char_lnext(tty, *cp++, flag);

				count--;

			}

		} else

			n_tty_receive_char_flagged(tty, *cp++, flag);

	}

}
@@ -1634,6 +1647,15 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp, 
	else if (tty->closing && !L_EXTPROC(tty))

		n_tty_receive_buf_closing(tty, cp, fp, count);

	else {

		if (ldata->lnext) {

			char flag = TTY_NORMAL;



			if (fp)

				flag = *fp++;

			n_tty_receive_char_lnext(tty, *cp++, flag);

			count--;

		}



		if (!preops && !I_PARMRK(tty))

			n_tty_receive_buf_fast(tty, cp, fp, count);

		else