Hi Peter, FYI, we noticed much increased vmap_area_lock contentions since this commit:
commit 20bafb3d23d108bc0a896eb8b7c1501f4f649b77 Author: Peter Hurley <[email protected]> Date: Sat Jun 15 10:21:19 2013 -0400 n_tty: Move buffers into n_tty_data Reduce pointer reloading and improve locality-of-reference; allocate read_buf and echo_buf within struct n_tty_data. Signed-off-by: Peter Hurley <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> :040000 040000 96d92e4e242c4b2ff11b25c005bccd093865b350 2822d87b2425c3e7adc7b722a20d739c9d4a3046 M drivers bisect run success # bad: [9cdfea961eeaf9b6b939fb9dc822a204a1d94d08] Merge remote-tracking branch 'ipvs-next/master' into devel-hourly-2013090112 # good: [d4e4ab86bcba5a72779c43dc1459f71fea3d89c8] Linux 3.11-rc5 git bisect start '9cdfea961eeaf9b6b939fb9dc822a204a1d94d08' 'd4e4ab86bcba5a72779c43dc1459f71fea3d89c8' '--' # good: [903bc7e8c2a4f9ef8e40aed615ed48023f9460e3] Merge remote-tracking branch 'spi/for-next' git bisect good 903bc7e8c2a4f9ef8e40aed615ed48023f9460e3 # bad: [d926318427c1fa8df182d3dcd7f802d7d0609225] Merge remote-tracking branch 'bcon/master' git bisect bad d926318427c1fa8df182d3dcd7f802d7d0609225 # bad: [adcb2bcd0dd2bb88f21180c8ffb9ec2549f4d883] Merge remote-tracking branch 'usb/usb-next' git bisect bad adcb2bcd0dd2bb88f21180c8ffb9ec2549f4d883 # good: [a83605266423437d8afe73cbd538df33cf8fb32b] Merge remote-tracking branch 'driver-core/driver-core-next' git bisect good a83605266423437d8afe73cbd538df33cf8fb32b # good: [224563b6ce034b82f8511969d9496113da34fb2c] Merge tag 'for-usb-next-2013-08-15' of git://git.kernel.org/pub/scm/linux/kernel/git/sarah/xhci into usb-next git bisect good 224563b6ce034b82f8511969d9496113da34fb2c # bad: [5284eba7b37dfeffe75bfdf81a13e9efebe0480a] serial/arc-uart: Handle Rx Error Interrupts w/o any data git bisect bad 5284eba7b37dfeffe75bfdf81a13e9efebe0480a # bad: [7d88d637a3c75257b7611f9feee0c17fa187ecc9] n_tty: Factor standard per-char i/o into separate fn git bisect bad 7d88d637a3c75257b7611f9feee0c17fa187ecc9 # good: [11b9faa44df76189b8346ff602a2c01c610c37eb] tty: Merge tty_buffer_find() into tty_buffer_alloc() git bisect good 11b9faa44df76189b8346ff602a2c01c610c37eb # good: [019ebdf9f26fd2e43b9e1af576835183e95dc82e] n_tty: Eliminate echo_commit memory barrier git bisect good 019ebdf9f26fd2e43b9e1af576835183e95dc82e # bad: [1bb9d562856279a217a4e581a803dee9bb48a708] n_tty: Rename process_char_map to char_map git bisect bad 1bb9d562856279a217a4e581a803dee9bb48a708 # good: [9dfd16ddea9bdbc8343340e543732db0a467ae32] n_tty: Avoid false-sharing echo buffer indices git bisect good 9dfd16ddea9bdbc8343340e543732db0a467ae32 # good: [8cb06c983822103da1cfe57b9901e60a00e61f67] n_tty: Remove alias ptrs in __receive_buf() git bisect good 8cb06c983822103da1cfe57b9901e60a00e61f67 # bad: [20bafb3d23d108bc0a896eb8b7c1501f4f649b77] n_tty: Move buffers into n_tty_data git bisect bad 20bafb3d23d108bc0a896eb8b7c1501f4f649b77 # first bad commit: [20bafb3d23d108bc0a896eb8b7c1501f4f649b77] n_tty: Move buffers into n_tty_data Compare of all good/bad commits in this bisect: lock_stat.vmap_area_lock.contentions 22000 ++-----------------------------------------------------------------+ 20000 ++O O O O O O O O OO O O OO O O O OO O O O O O O O O | O OO OO O O O | 18000 ++ | 16000 ++ | | | 14000 ++ | 12000 ++ | 10000 ++ | | | 8000 ++ | 6000 ++ | | | 4000 *+*.**.*.*.*.**.*.*.*.*.**.*.*.*.**.*.*.*.**.*.*.*.*.**.*.*.*.**.*.* 2000 ++-----------------------------------------------------------------+ lock_stat.vmap_area_lock.contentions.get_vmalloc_info 45000 ++-----------------------------------------------------------------+ | O O O O O O O | 40000 O+ OO O O O OO O O O OO O O OO O O OO O O OO O O O | 35000 ++ | | | 30000 ++ | | | 25000 ++ | | | 20000 ++ | 15000 ++ | | | 10000 ++ | | *.*. *. .*. .*. .*.*. | 5000 *+*-**-*-*-*-**-*-*-*-*-*----*-*-*--*---*-**-*-*-*---**-----*-**-*-*
>From 20bafb3d23d108bc0a896eb8b7c1501f4f649b77 Mon Sep 17 00:00:00 2001 From: Peter Hurley <[email protected]> Date: Sat, 15 Jun 2013 10:21:19 -0400 Subject: [PATCH] n_tty: Move buffers into n_tty_data Reduce pointer reloading and improve locality-of-reference; allocate read_buf and echo_buf within struct n_tty_data. Signed-off-by: Peter Hurley <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- drivers/tty/n_tty.c | 25 +++++++++---------------- 1 file changed, 9 insertions(+), 16 deletions(-) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index d6eba99..51cbdd2 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -105,9 +105,9 @@ struct n_tty_data { unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1; /* shared by producer and consumer */ - char *read_buf; + char read_buf[N_TTY_BUF_SIZE]; DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE); - unsigned char *echo_buf; + unsigned char echo_buf[N_TTY_BUF_SIZE]; int minimum_to_wake; @@ -1695,9 +1695,7 @@ static void n_tty_close(struct tty_struct *tty) if (tty->link) n_tty_packet_mode_flush(tty); - kfree(ldata->read_buf); - kfree(ldata->echo_buf); - kfree(ldata); + vfree(ldata); tty->disc_data = NULL; } @@ -1715,7 +1713,8 @@ static int n_tty_open(struct tty_struct *tty) { struct n_tty_data *ldata; - ldata = kzalloc(sizeof(*ldata), GFP_KERNEL); + /* Currently a malloc failure here can panic */ + ldata = vmalloc(sizeof(*ldata)); if (!ldata) goto err; @@ -1723,16 +1722,14 @@ static int n_tty_open(struct tty_struct *tty) mutex_init(&ldata->atomic_read_lock); mutex_init(&ldata->output_lock); - /* These are ugly. Currently a malloc failure here can panic */ - ldata->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL); - ldata->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL); - if (!ldata->read_buf || !ldata->echo_buf) - goto err_free_bufs; - tty->disc_data = ldata; reset_buffer_flags(tty->disc_data); ldata->column = 0; + ldata->canon_column = 0; ldata->minimum_to_wake = 1; + ldata->num_overrun = 0; + ldata->no_room = 0; + ldata->lnext = 0; tty->closing = 0; /* indicate buffer work may resume */ clear_bit(TTY_LDISC_HALTED, &tty->flags); @@ -1740,10 +1737,6 @@ static int n_tty_open(struct tty_struct *tty) tty_unthrottle(tty); return 0; -err_free_bufs: - kfree(ldata->read_buf); - kfree(ldata->echo_buf); - kfree(ldata); err: return -ENOMEM; } -- 1.8.3.2
