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n_tty: Factor LNEXT processing from per-char i/o path
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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: Peter Hurley <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
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@peterhurley @gregkh
peterhurley authored and gregkh committed Jul 24, 2013
1 parent 4b29349 commit e60d27c
Showing 1 changed file with 94 additions and 72 deletions.
166 changes: 94 additions & 72 deletions drivers/tty/n_tty.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -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;
}
}

Expand All @@ -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))
Expand All @@ -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;
Expand All @@ -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);
Expand All @@ -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)) {
Expand Down Expand Up @@ -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;
}
}

Expand All @@ -1389,77 +1390,56 @@ 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)) {
start_tty(tty);
process_echoes(tty);
}
if (L_ECHO(tty)) {
finish_erasing(ldata);
/* Record the column of first canon char. */
if (ldata->canon_head == ldata->read_head)
echo_set_canon_col(ldata);
echo_char(c, tty);
commit_echoes(tty);
}
parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
if (parmrk)
put_tty_queue(c, ldata);
put_tty_queue(c, ldata);
return;
if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
start_tty(tty);
process_echoes(tty);
}
if (L_ECHO(tty)) {
finish_erasing(ldata);
/* Record the column of first canon char. */
if (ldata->canon_head == ldata->read_head)
echo_set_canon_col(ldata);
echo_char(c, tty);
commit_echoes(tty);
}
parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
if (parmrk)
put_tty_queue(c, ldata);
put_tty_queue(c, ldata);
}

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
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)) {
start_tty(tty);
process_echoes(tty);
}
if (L_ECHO(tty)) {
finish_erasing(ldata);
/* Record the column of first canon char. */
if (ldata->canon_head == ldata->read_head)
echo_set_canon_col(ldata);
echo_char(c, tty);
commit_echoes(tty);
}
put_tty_queue(c, ldata);
return;
if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
start_tty(tty);
process_echoes(tty);
}

n_tty_receive_char_special(tty, c);
if (L_ECHO(tty)) {
finish_erasing(ldata);
/* Record the column of first canon char. */
if (ldata->canon_head == ldata->read_head)
echo_set_canon_col(ldata);
echo_char(c, tty);
commit_echoes(tty);
}
put_tty_queue(c, ldata);
}

static inline void
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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);
}
Expand All @@ -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);
}
}
Expand All @@ -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
Expand Down

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