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linux/drivers
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Linus Torvalds f23eb2b2b2 tty: stop using "delayed_work" in the tty layer 
Using delayed-work for tty flip buffers ends up causing us to wait for
the next tick to complete some actions.  That's usually not all that
noticeable, but for certain latency-critical workloads it ends up being
totally unacceptable.

As an extreme case of this, passing a token back-and-forth over a pty
will take two ticks per iteration, so even just a thousand iterations
will take 8 seconds assuming a common 250Hz configuration.

Avoiding the whole delayed work issue brings that ping-pong test-case
down to 0.009s on my machine.

In more practical terms, this latency has been a performance problem for
things like dive computer simulators (simulating the serial interface
using the ptys) and for other environments (Alan mentions a CP/M emulator).

Reported-by: Jef Driesen <jefdriesen@telenet.be>
Acked-by: Greg KH <gregkh@suse.de>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
History 2011-03-22 16:17:32 -07:00
..
accessibility drop explicit include of autoconf.h 2009-12-12 13:08:15 +01:00
acpi Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6 2011-03-16 19:01:29 -07:00
amba ARM: 6758/1: amba: support pm ops 2011-02-23 16:26:46 +00:00
ata Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc 2011-03-18 06:31:43 -07:00
atm Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-03-18 10:37:40 -07:00
auxdisplay auxdisplay: section cleanup in cfag12864bfb driver 2010-05-25 08:07:09 -07:00
base Merge branch 'driver-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core-2.6 2011-03-16 15:05:40 -07:00
block Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-03-18 10:37:40 -07:00
bluetooth Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-03-18 10:37:40 -07:00
cdrom cdrom: support devices that have check_events but not media_changed 2011-02-09 14:22:37 +01:00
char Merge branch 'trivial' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6 2011-03-20 18:14:55 -07:00
clk ARM: 6483/1: arm & sh: factorised duplicated clkdev.c 2010-11-26 10:51:04 +00:00
clocksource drivers/clocksource/tcb_clksrc.c: fix init sequence 2011-01-26 10:50:04 +10:00
connector connector: Convert char *name to const char *name 2011-02-23 13:22:26 -08:00
cpufreq [CPUFREQ] Remove the pm_message_t argument from driver suspend 2011-03-16 17:54:33 -04:00
cpuidle Merge branch 'master' into for-next 2011-02-15 10:24:31 +01:00
crypto Merge branch 'devicetree/next' of git://git.secretlab.ca/git/linux-2.6 2011-03-16 17:28:10 -07:00
dca dca: remove unneeded NULL check 2011-01-13 08:03:09 -08:00
dio m68k: don't export static inline functions 2009-12-06 11:18:28 +01:00
dma Merge branch 'trivial' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6 2011-03-20 18:14:55 -07:00
edac Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-03-18 10:37:40 -07:00
eisa eisa: fix coding style for eisa bus code 2010-03-06 11:26:32 -08:00
firewire Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394-2.6 2011-03-21 10:05:22 -07:00
firmware Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-03-18 10:37:40 -07:00
gpio Merge branch 'spi/next' of git://git.secretlab.ca/git/linux-2.6 2011-03-18 10:56:02 -07:00
gpu Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-03-18 10:37:40 -07:00
hid Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2011-03-19 22:27:06 -07:00
hwmon hwmon: (ads1015) Make gain and datarate configurable 2011-03-21 17:59:37 +01:00
hwspinlock drivers: hwspinlock: add OMAP implementation 2011-02-17 09:52:03 -08:00
i2c Merge branch 'for-linus/2639/i2c-2' of git://git.fluff.org/bjdooks/linux 2011-03-22 10:05:27 -07:00
ide ide: change to new flag variable 2011-03-17 14:05:34 +01:00
idle intel_idle: disable Atom/Lincroft HW C-state auto-demotion 2011-02-17 17:08:48 -05:00
ieee802154 ieee802154: change to new flag variable 2011-03-17 14:05:34 +01:00
infiniband Merge branch 'kvm-updates/2.6.39' of git://git.kernel.org/pub/scm/virt/kvm/kvm 2011-03-17 18:40:35 -07:00
input Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2011-03-19 22:27:06 -07:00
isdn Merge branch 'trivial' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6 2011-03-20 18:14:55 -07:00
leds leds/leds-gpio: merge platform_driver with of_platform_driver 2011-02-28 01:36:39 -07:00
lguest lguest: compile fixes 2011-01-20 21:37:29 +10:30
macintosh Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc 2011-03-18 06:31:43 -07:00
mca mca: struct device - replace bus_id with dev_name(), dev_set_name() 2009-03-24 16:38:23 -07:00
md Merge git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6 2011-03-17 17:54:40 -07:00
media Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2011-03-19 22:27:06 -07:00
memstick memstick: change to new flag variable 2011-03-17 14:05:34 +01:00
message Merge branch 'trivial' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6 2011-03-20 18:14:55 -07:00
mfd Merge branch 'devel-stable' of master.kernel.org:/home/rmk/linux-2.6-arm 2011-03-17 19:08:06 -07:00
misc Move lis3lv02d drivers to drivers/misc 2011-03-21 17:59:36 +01:00
mmc Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/cjb/mmc 2011-03-18 22:32:40 -07:00
mtd Merge branch 'linux-next' of git://git.infradead.org/ubifs-2.6 2011-03-18 10:50:27 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6 2011-03-22 09:25:34 -07:00
nfc drivers/nfc/pn544.c: add missing regulator 2011-02-25 15:07:36 -08:00
nubus include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
of Merge branch 'devicetree/next' of git://git.secretlab.ca/git/linux-2.6 2011-03-16 17:28:10 -07:00
oprofile oprofile, s390: Rework hwsampler implementation 2011-02-15 11:10:20 +01:00
parisc [PARISC] Convert to new irq_chip functions 2011-02-10 10:22:14 -06:00
parport dt/sparc: Eliminate users of of_platform_{,un}register_driver 2011-02-28 01:36:39 -07:00
pci Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6 2011-03-18 10:56:44 -07:00
pcmcia Merge branch 'devicetree/next' of git://git.secretlab.ca/git/linux-2.6 2011-03-16 17:28:10 -07:00
platform hp_accel: Fix driver name 2011-03-21 17:59:36 +01:00
pnp Merge branch 'pnp' into release 2011-01-12 04:59:44 -05:00
power Merge git://git.infradead.org/battery-2.6 2011-01-14 09:25:59 -08:00
pps pps: change to new flag variable 2011-03-17 14:05:35 +01:00
ps3 powerpc/ps3: Replace the use of <module>-objs with <module>-y 2010-11-29 15:48:19 +11:00
rapidio rapidio: change to new flag variable 2011-03-17 14:05:35 +01:00
regulator regulator, mc13xxx: Remove pointless test for unsigned less than zero 2011-02-25 08:51:07 +00:00
rtc Merge branch 'trivial' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild-2.6 2011-03-20 18:14:55 -07:00
s390 Merge git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6 2011-03-17 17:54:40 -07:00
sbus dt/sparc: Eliminate users of of_platform_{,un}register_driver 2011-02-28 01:36:39 -07:00
scsi sd: Fail discard requests when logical block provisioning has been disabled 2011-03-22 09:35:53 -07:00
sfi SFI: use ioremap_cache() instead of ioremap() 2011-01-11 23:27:25 -05:00
sh sh: update INTC to clear IRQ sense valid flag 2011-01-19 19:02:35 +09:00
sn include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
spi Merge branch 'spi/next' of git://git.secretlab.ca/git/linux-2.6 2011-03-18 10:56:02 -07:00
ssb Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-next-2.6 into for-davem 2011-02-22 15:10:22 -05:00
staging Merge branch 'config' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/bkl 2011-03-16 17:21:00 -07:00
target Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-03-18 10:37:40 -07:00
tc include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
telephony Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-01-13 10:05:56 -08:00
thermal ACPI: Fix build for CONFIG_NET unset 2011-02-28 18:00:31 -08:00
tty tty: stop using "delayed_work" in the tty layer 2011-03-22 16:17:32 -07:00
uio UIO: add PRUSS UIO driver support 2011-03-07 13:10:27 -08:00
usb USB: Move runtime PM callbacks to usb_device_pm_ops 2011-03-18 19:55:36 +01:00
uwb drivers:uwb:scan.c remove one to many l's in the word. 2011-02-25 11:52:21 -08:00
vhost vhost-net: remove unlocked use of receive_queue 2011-03-13 23:08:19 +02:00
video matroxfb: remove incorrect Matrox G200eV support 2011-03-21 15:50:30 -07:00
virtio virtio: remove virtio-pci root device 2011-01-20 21:37:30 +10:30
vlynq MIPS: Add missing #inclusions of <linux/irq.h> 2010-10-07 14:08:54 +01:00
w1 Merge branches 'devel-cleanup', 'devel-board', 'devel-early-init' and 'devel-ti816x' into omap-for-linus 2011-02-16 11:32:38 -08:00
watchdog Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2011-03-18 10:37:40 -07:00
xen Merge branch 'stable/xen.pm.bug-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen 2011-03-17 18:37:42 -07:00
zorro BKL: remove extraneous #include <smp_lock.h> 2010-11-17 08:59:32 -08:00
Kconfig drivers: hwspinlock: add framework 2011-02-17 09:52:03 -08:00
Makefile drivers: hwspinlock: add framework 2011-02-17 09:52:03 -08:00