Paolo Valente
3c395a969a
null_blk: set a separate timer for each command ...
For the Timer IRQ mode (i.e., when command completions are delayed),
there is one timer for each CPU. Each of these timers
. has a completion queue associated with it, containing all the
command completions to be executed when the timer fires;
. is set, and a new completion-to-execute is inserted into its
completion queue, every time the dispatch code for a new command
happens to be executed on the CPU related to the timer.
This implies that, if the dispatch of a new command happens to be
executed on a CPU whose timer has already been set, but has not yet
fired, then the timer is set again, to the completion time of the
newly arrived command. When the timer eventually fires, all its queued
completions are executed.
This way of handling delayed command completions entails the following
problem: if more than one command completion is inserted into the
queue of a timer before the timer fires, then the expiration time for
the timer is moved forward every time each of these completions is
enqueued. As a consequence, only the last completion enqueued enjoys a
correct execution time, while all previous completions are unjustly
delayed until the last completion is executed (and at that time they
are executed all together).
Specifically, if all the above completions are enqueued almost at the
same time, then the problem is negligible. On the opposite end, if
every completion is enqueued a while after the previous completion was
enqueued (in the extreme case, it is enqueued only right before the
timer would have expired), then every enqueued completion, except for
the last one, experiences an inflated delay, proportional to the number
of completions enqueued after it. In the end, commands, and thus I/O
requests, may be completed at an arbitrarily lower rate than the
desired one.
This commit addresses this issue by replacing per-CPU timers with
per-command timers, i.e., by associating an individual timer with each
command.
Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
Signed-off-by: Arianna Avanzini <avanzini@google.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2015-12-01 10:52:08 -07:00
Merge branches 'acpi-smbus', 'acpi-ec' and 'acpi-pci'
2015-11-20 01:22:52 +01:00
SCSI misc on 20151113
2015-11-13 20:35:54 -08:00
Merge branch 'pm-sleep'
2015-11-20 01:22:33 +01:00
null_blk: set a separate timer for each command
2015-12-01 10:52:08 -07:00
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
2015-11-10 18:11:41 -08:00
ARM: SoC driver updates for v4.4
2015-11-10 15:00:03 -08:00
ipmi watchdog : add panic_wdt_timeout parameter
2015-11-16 06:28:43 -06:00
h8300 update for v4.4
2015-11-12 15:26:39 -08:00
clocksource: Disallow drivers for ARCH_USES_GETTIMEOFFSET
2015-11-16 19:07:08 +01:00
mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd
2015-11-06 17:50:42 -08:00
Merge branches 'pm-cpufreq' and 'acpi-cppc'
2015-11-20 01:22:10 +01:00
Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6
2015-11-17 09:40:05 -08:00
dmaengine: at_hdmac: use %pad format string for dma_addr_t
2015-11-16 09:21:05 +05:30
dma-buf/fence: add fence_wait_any_timeout function v2
2015-10-30 01:16:16 -04:00
asm-generic cleanups
2015-11-06 14:22:15 -08:00
Merge branches 'ib-extcon-mfd-4.4', 'ib-mfd-i2c-v4.4', 'ib-mfd-power-4.4', 'ib-mfd-regmap-4.4' and 'ib-mfd-regulator-4.4' into ibs-for-mfd-merged
2015-10-26 14:48:22 +00:00
IEEE 1394 subsystem patch:
2015-11-11 10:21:34 -08:00
ARM: SoC driver updates for v4.4
2015-11-10 15:00:03 -08:00
fpga: socfpga: Fix check of return value of devm_request_irq
2015-10-29 15:20:25 -07:00
asm-generic cleanups
2015-11-06 14:22:15 -08:00
Merge tag 'drm-intel-fixes-2015-11-19' of git://anongit.freedesktop.org/drm-intel into drm-fixes
2015-11-20 09:45:31 +10:00
HID: wacom: fixup quirks setup for WACOM_DEVICETYPE_PAD
2015-11-17 00:24:14 +01:00
hsi: controllers:remove redundant code
2015-10-30 16:10:40 +01:00
drivers/hv: share Hyper-V SynIC constants with userspace
2015-11-04 16:24:33 +01:00
hwmon: (scpi) skip unsupported sensors properly
2015-11-16 09:59:50 -08:00
Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending
2015-11-13 20:04:17 -08:00
i2c: i801: add Intel Lewisburg device IDs
2015-11-20 16:22:21 +01:00
mm, page_alloc: rename __GFP_WAIT to __GFP_RECLAIM
2015-11-06 17:50:42 -08:00
First set of IIO fixes for the 4.4 cycle.
2015-11-18 13:15:50 -08:00
SCSI misc on 20151113
2015-11-13 20:35:54 -08:00
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input
2015-11-13 21:41:14 -08:00
s390/pci_dma: handle dma table failures
2015-11-09 09:10:49 +01:00
irqchip/gic: Add save/restore of the active state
2015-11-17 14:25:59 +01:00
TTY/Serial driver patches for 4.4-rc1
2015-11-04 21:35:12 -08:00
spi: Updates for v4.4
2015-11-05 13:15:12 -08:00
lightnvm: missing nvm_lock acquire
2015-11-29 14:34:58 -07:00
mailbox: mailbox-test: avoid reading iomem twice
2015-11-04 14:03:04 +05:30
mcb: Destroy IDA on module unload
2015-10-29 09:02:16 +09:00
dm thin: fix regression in advertised discard limits
2015-11-23 14:54:46 -05:00
various: fix pci_set_dma_mask return value checking
2015-11-20 16:17:32 -08:00
ARM: SoC driver updates for v4.4
2015-11-10 15:00:03 -08:00
SCSI queue for 4.4.
2015-11-12 07:06:18 -05:00
asm-generic cleanups
2015-11-06 14:22:15 -08:00
Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending
2015-11-13 20:04:17 -08:00
mmc: remove bondage between REQ_META and reliable write
2015-11-09 14:04:52 +01:00
mtd: nand: fix shutdown/reboot for multi-chip systems
2015-11-16 10:51:39 -08:00
various: fix pci_set_dma_mask return value checking
2015-11-20 16:17:32 -08:00
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
2015-11-10 18:11:41 -08:00
NTB: fix 32-bit compiler warning
2015-11-08 16:24:43 -05:00
libnvdimm, pmem: fix size trim in pmem_direct_access()
2015-11-12 09:55:23 -08:00
lightnvm: unconverted ppa returned in get_bb_tbl
2015-11-29 14:34:58 -07:00
More power management and ACPI updates for v4.4-rc1
2015-11-12 11:50:33 -08:00
pci: remove pci_dma_supported
2015-11-10 16:32:11 -08:00
Merge branches 'acpi-smbus', 'acpi-ec' and 'acpi-pci'
2015-11-20 01:22:52 +01:00
arm64 updates for 4.4:
2015-11-04 14:47:13 -08:00
phy: qcom-ufs: fix build error when the component is built as a module
2015-11-09 17:44:24 -05:00
This is the bulk of GPIO changes for v4.4:
2015-11-02 12:59:12 -08:00
platform/chrome: Branch for v4.4
2015-11-13 21:53:18 -08:00
- New Device Support
2015-11-06 10:23:50 -08:00
pwm: Changes for v4.4-rc1
2015-11-11 09:16:10 -08:00
spi: Updates for v4.4
2015-11-05 13:15:12 -08:00
RTC for 4.4
2015-11-10 10:01:21 -08:00
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux
2015-11-18 08:59:29 -08:00
SCSI misc on 20151113
2015-11-13 20:35:54 -08:00
drivers: sh: Get rid of CONFIG_ARCH_SHMOBILE_MULTI
2015-11-17 02:12:46 +09:00
ARM: SoC driver updates for v4.4
2015-11-10 15:00:03 -08:00
Merge remote-tracking branches 'spi/topic/s3c64xx', 'spi/topic/ti-qspi' and 'spi/topic/txx9' into spi-next
2015-11-04 11:02:16 +00:00
char/misc drivers for 4.4-rc1
2015-11-04 22:15:15 -08:00
ssb: add Kconfig entry for compiling SoC related code
2015-10-28 21:05:21 +02:00
Revert "Staging: wilc1000: coreconfigurator: Drop unneeded wrapper functions"
2015-11-18 13:22:44 -08:00
SCSI misc on 20151113
2015-11-13 20:35:54 -08:00
thermal: rockchip: fix compile error
2015-11-11 19:52:39 -08:00
serial: export fsl8250_handle_irq
2015-11-20 16:19:54 -08:00
usblp: do not set TASK_INTERRUPTIBLE before lock
2015-11-19 16:31:42 -08:00
driver core update for 4.4-rc1
2015-11-04 21:50:37 -08:00
VFIO updates for v4.4-rc1
2015-11-13 17:05:32 -08:00
Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending
2015-11-13 20:04:17 -08:00
fbdev changes for 4.4
2015-11-10 10:00:09 -08:00
char/misc drivers for 4.4-rc1
2015-11-04 22:15:15 -08:00
power supply and reset changes for the v4.4 series
2015-11-05 12:28:15 -08:00
Merge git://www.linux-watchdog.org/linux-watchdog
2015-11-10 10:11:12 -08:00
Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending
2015-11-13 20:04:17 -08:00
char/misc drivers for 4.4-rc1
2015-11-04 22:15:15 -08:00
null_blk: register as a LightNVM device
2015-11-16 15:22:28 -07:00
3c395a969a