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Dave Airlie dd0c41f8a7 efifb: allow user to disable write combined mapping. 
This patch allows the user to disable write combined mapping
of the efifb framebuffer console using an nowc option.

A customer noticed major slowdowns while logging to the console
with write combining enabled, on other tasks running on the same
CPU. (10x or greater slow down on all other cores on the same CPU
as is doing the logging).

I reproduced this on a machine with dual CPUs.
Intel(R) Xeon(R) CPU E5-2609 v3 @ 1.90GHz (6 core)

I wrote a test that just mmaps the pci bar and writes to it in
a loop, while this was running in the background one a single
core with (taskset -c 1), building a kernel up to init/version.o
(taskset -c 8) went from 13s to 133s or so. I've yet to explain
why this occurs or what is going wrong I haven't managed to find
a perf command that in any way gives insight into this.

    11,885,070,715      instructions              #    1.39  insns per cycle
vs
    12,082,592,342      instructions              #    0.13  insns per cycle

is the only thing I've spotted of interest, I've tried at least:
dTLB-stores,dTLB-store-misses,L1-dcache-stores,LLC-store,LLC-store-misses,LLC-load-misses,LLC-loads,\mem-loads,mem-stores,iTLB-loads,iTLB-load-misses,cache-references,cache-misses

For now it seems at least a good idea to allow a user to disable write
combining if they see this until we can figure it out.

Note also most users get a real framebuffer driver loaded when kms
kicks in, it just happens on these machines the kernel didn't support
the gpu specific driver.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Acked-by: Peter Jones <pjones@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
2017-07-31 18:45:41 +02:00
..
ABI MTD updates for v4.13-rc1: 2017-07-13 12:07:44 -07:00
accounting
acpi This is the bulk of GPIO changes for the v4.13 series: 2017-07-07 12:40:27 -07:00
admin-guide Merge branch 'akpm' (patches from Andrew) 2017-07-06 22:27:08 -07:00
aoe
arm ARM: at91: Documentation: add armv7m families 2017-06-02 10:11:09 +02:00
arm64 IOMMU Updates for Linux v4.13 2017-07-12 10:00:04 -07:00
auxdisplay
backlight
blackfin
block bio-integrity: fold bio_integrity_enabled to bio_integrity_prep 2017-07-03 16:56:24 -06:00
blockdev remove the mg_disk driver 2017-04-14 14:00:49 -06:00
bus-devices
cdrom cdrom: Make device operations read-only 2017-02-14 08:29:56 -07:00
cgroup-v1 mm, vmpressure: pass-through notification support 2017-07-10 16:32:31 -07:00
cma
connector
console
core-api A set of fixes for various warnings, including the one caused by the 2017-07-13 13:44:54 -07:00
cpu-freq cpufreq: intel_pstate: Document the current behavior and user interface 2017-05-14 02:06:03 +02:00
cpuidle
cris
crypto KEYS: Add documentation for asymmetric keyring restrictions 2017-07-14 11:01:38 +10:00
dev-tools linux-kselftest-4.13-rc1-update 2017-07-07 14:04:47 -07:00
device-mapper dm raid: bump target version 2017-07-25 14:54:20 -04:00
devicetree Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2017-07-28 12:31:49 -07:00
dmaengine
doc-guide kernel-doc: describe the `literal` syntax 2017-05-16 08:44:24 -03:00
driver-api A set of fixes for various warnings, including the one caused by the 2017-07-13 13:44:54 -07:00
driver-model pci-v4.13-changes 2017-07-08 15:51:57 -07:00
early-userspace Documentation: Fix dead URLs to ftp.kernel.org 2017-03-29 15:46:06 -06:00
EDID drm: use .hword to represent 16-bit numbers 2017-03-30 10:15:19 +02:00
extcon extcon: Remove porting compatibility of swich class 2017-04-06 10:55:24 +09:00
fault-injection fault-inject: add /proc/<pid>/fail-nth 2017-07-14 15:05:13 -07:00
fb efifb: allow user to disable write combined mapping. 2017-07-31 18:45:41 +02:00
features powerpc updates for 4.12 part 1. 2017-05-05 11:36:44 -07:00
filesystems Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-15 12:00:42 -07:00
firmware_class firmware: revamp firmware documentation 2017-01-11 09:42:59 +01:00
fmc
fpga fpga: Add scatterlist based programming 2017-02-10 15:20:44 +01:00
frv
gpio gpio: return NULL from gpiod_get_optional when GPIOLIB is disabled 2017-03-15 11:16:30 +01:00
gpu main drm pull for v4.13 2017-07-09 18:48:37 -07:00
hid Documentation: hid: fix path to input bus definitions 2017-03-13 17:15:19 -06:00
hwmon hwmon: (pmbus) move header file out of I2C realm 2017-06-11 17:08:19 -07:00
i2c i2c: i801: Add support for Intel Cannon Lake 2017-06-19 16:17:41 +02:00
ia64
ide
iio
infiniband IB/opa-vnic: Virtual Network Interface Controller (VNIC) documentation 2017-04-20 12:01:06 -04:00
input A set of fixes for various warnings, including the one caused by the 2017-07-13 13:44:54 -07:00
ioctl scsi: cxlflash: Introduce host ioctl support 2017-06-26 15:01:11 -04:00
isdn
kbuild Kbuild thin archives updates for v4.13 2017-07-07 15:11:12 -07:00
kdump kexec/kdump: minor Documentation updates for arm64 and Image 2017-07-12 16:26:00 -07:00
kernel-hacking There has been a fair amount of activity in the docs tree this time 2017-07-03 21:13:25 -07:00
laptops
leds Documentaion: leds: leds-lp55xx.txt: Fix typos 2017-03-17 13:06:14 -06:00
lightnvm lightnvm: physical block device (pblk) target 2017-04-16 10:06:33 -06:00
livepatch livepatch: allow removal of a disabled patch 2017-03-08 09:38:43 +01:00
locking locking/ww_mutex/Documentation: Update the design document 2017-01-14 11:14:55 +01:00
m68k
md Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/shli/md 2017-05-03 10:05:38 -07:00
media media updates for v4.13-rc1 2017-07-06 11:15:19 -07:00
memory-devices
metag
mic
mips
misc-devices Documentation: misc-devices: Add Documentation for pci-endpoint-test driver 2017-04-28 10:23:19 -05:00
mmc MMC core: 2017-05-02 17:34:32 -07:00
mn10300
mtd
namespaces
netlabel
networking net: Fix minor code bug in timestamping.txt 2017-07-11 13:34:54 -07:00
nfc
nios2
nvdimm
nvmem
parisc
PCI docs: update old references for DocBook from the documentation 2017-05-16 08:44:19 -03:00
pcmcia
perf perf: qcom: Add L3 cache PMU driver 2017-04-03 18:53:50 +01:00
phy
platform
power power supply and reset changes for the v4.13 series 2017-07-04 14:25:14 -07:00
powerpc powerpc updates for 4.13 2017-07-07 13:55:45 -07:00
pps
process Kbuild thin archives updates for v4.13 2017-07-07 15:11:12 -07:00
pti
ptp
rapidio
RCU rcu: Remove debugfs tracing 2017-06-08 18:52:43 -07:00
s390 docs: add documentation for vfio-ccw 2017-03-31 12:55:11 +02:00
scheduler sched/deadline: Add documentation about GRUB reclaiming 2017-06-08 10:31:56 +02:00
scsi scsi: make asynchronous aborts mandatory 2017-04-06 13:07:33 -04:00
security KEYS: Add documentation for asymmetric keyring restrictions 2017-07-14 11:01:38 +10:00
serial tty: n_gsm: do not send/receive in ldisc close path 2017-06-03 18:48:52 +09:00
sh docs-rst: convert sh book to ReST 2017-05-16 08:44:18 -03:00
sound sound updates for 4.13-rc1 2017-07-06 10:56:51 -07:00
sparc Documentation/sparc: Steps for sending break on sunhv console 2017-02-23 08:27:25 -08:00
sphinx Docs: clean up some DocBook loose ends 2017-06-23 14:17:38 -06:00
sphinx-static
spi spi: Document SPI slave controller support 2017-05-26 13:11:00 +01:00
sysctl mm: document highmem_is_dirtyable sysctl 2017-07-10 16:32:32 -07:00
target Documentation/target: add an example script to configure an iSCSI target 2017-05-01 22:21:35 -07:00
thermal Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/rzhang/linux 2017-05-12 11:58:45 -07:00
timers rcu: Eliminate NOCBs CPU-state Kconfig options 2017-06-08 18:52:43 -07:00
trace A few more minor updates: 2017-07-13 13:17:19 -07:00
translations kokr/memory-barriers.txt: Fix obsolete link to atomic_ops.txt 2017-07-12 16:56:40 -06:00
usb usb: gadget: add f_uac1 variant based on a new u_audio api 2017-06-19 09:22:47 +03:00
userspace-api doc: ReSTify no_new_privs.txt 2017-05-18 10:30:09 -06:00
virtual kvm: x86: hyperv: make VP_INDEX managed by userspace 2017-07-14 16:28:18 +02:00
vm ksm: introduce ksm_max_page_sharing per page deduplication limit 2017-07-06 16:24:31 -07:00
w1 w1: add documentation for w1_ds2438 2017-03-17 15:10:49 +09:00
watchdog watchdog: uniphier: add UniPhier watchdog driver 2017-07-03 13:58:55 +02:00
wimax
x86 x86/mce: Update bootlog description to reflect behavior on AMD 2017-06-14 07:32:10 +02:00
xtensa of: update ePAPR references to point to Devicetree Specification 2017-06-22 11:22:06 -05:00
.gitignore
00-INDEX linux-kselftest-4.13-rc1-update 2017-07-07 14:04:47 -07:00
bcache.txt bcache.txt: standardize document format 2017-07-14 13:51:27 -06:00
bt8xxgpio.txt bt8xxgpio.txt: standardize document format 2017-07-14 13:51:27 -06:00
btmrvl.txt btmrvl.txt: standardize document format 2017-07-14 13:51:27 -06:00
bus-virt-phys-mapping.txt bus-virt-phys-mapping.txt: standardize document format 2017-07-14 13:51:28 -06:00
cachetlb.txt cachetlb.txt: standardize document format 2017-07-14 13:51:28 -06:00
cgroup-v2.txt cgroup-v2.txt: standardize document format 2017-07-14 13:58:13 -06:00
Changes
circular-buffers.txt circular-buffers.txt: standardize document format 2017-07-14 13:51:29 -06:00
clk.txt clk.txt: standardize document format 2017-07-14 13:51:29 -06:00
CodingStyle
conf.py Docs: Fix breakage with Sphinx 1.5 and upper 2017-06-23 13:45:37 -06:00
cpu-load.txt cpu-load: standardize document format 2017-07-14 13:51:30 -06:00
cputopology.txt cputopology.txt: standardize document format 2017-07-14 13:51:30 -06:00
crc32.txt crc32.txt: standardize document format 2017-07-14 13:51:30 -06:00
dcdbas.txt dcdbas.txt: standardize document format 2017-07-14 13:51:31 -06:00
debugging-modules.txt
debugging-via-ohci1394.txt debugging-via-ohci1394.txt: standardize document format 2017-07-14 13:51:34 -06:00
dell_rbu.txt dell_rbu.txt: standardize document format 2017-07-14 13:58:12 -06:00
digsig.txt digsig.txt: standardize document format 2017-07-14 13:51:31 -06:00
DMA-API-HOWTO.txt DMA-API-HOWTO.txt: standardize document format 2017-07-14 13:51:32 -06:00
DMA-API.txt DMA-API.txt: standardize document format 2017-07-14 13:51:32 -06:00
DMA-attributes.txt DMA-attributes.txt: standardize document format 2017-07-14 13:51:33 -06:00
DMA-ISA-LPC.txt DMA-ISA-LPC.txt: standardize document format 2017-07-14 13:51:33 -06:00
docutils.conf
dontdiff GCC plugin updates: 2017-07-05 11:46:59 -07:00
efi-stub.txt efi-stub.txt: standardize document format 2017-07-14 13:51:34 -06:00
eisa.txt eisa.txt: standardize document format 2017-07-14 13:51:34 -06:00
flexible-arrays.txt flexible-arrays.txt: standardize document format 2017-07-14 13:51:35 -06:00
futex-requeue-pi.txt futex-requeue-pi.txt: standardize document format 2017-07-14 13:51:35 -06:00
gcc-plugins.txt gcc-plugins.txt: standardize document format 2017-07-14 13:51:36 -06:00
highuid.txt highuid.txt: standardize document format 2017-07-14 13:51:36 -06:00
hw_random.txt hw_random.txt: standardize document format 2017-07-14 13:51:37 -06:00
hwspinlock.txt hwspinlock.txt: standardize document format 2017-07-14 13:51:37 -06:00
index.rst Make the main documentation title less Geocities 2017-06-23 14:02:27 -06:00
intel_txt.txt intel_txt.txt: standardize document format 2017-07-14 13:51:38 -06:00
Intel-IOMMU.txt Intel-IOMMU.txt: standardize document format 2017-07-14 13:51:38 -06:00
io_ordering.txt io_ordering.txt: standardize document format 2017-07-14 13:51:39 -06:00
io-mapping.txt io-mapping.txt: standardize document format 2017-07-14 13:51:38 -06:00
iostats.txt iostats.txt: update it to cover recent Kernels 2017-07-14 13:51:40 -06:00
IPMI.txt IPMI.txt: standardize document format 2017-07-14 13:51:40 -06:00
IRQ-affinity.txt IRQ-affinity.txt: standardize document format 2017-07-14 13:51:41 -06:00
IRQ-domain.txt IRQ-domain.txt: standardize document format 2017-07-14 13:51:41 -06:00
IRQ.txt IRQ.txt: add a markup for its title 2017-07-14 13:51:42 -06:00
irqflags-tracing.txt irqflags-tracing.txt: standardize document format 2017-07-14 13:51:42 -06:00
isa.txt isa.txt: standardize document format 2017-07-14 13:51:43 -06:00
isapnp.txt isapnp.txt: promote title level 2017-07-14 13:51:43 -06:00
kernel-doc-nano-HOWTO.txt docs: update old references for DocBook from the documentation 2017-05-16 08:44:19 -03:00
kernel-per-CPU-kthreads.txt kernel-per-CPU-kthreads.txt: standardize document format 2017-07-14 13:51:43 -06:00
kobject.txt kobject.txt: standardize document format 2017-07-14 13:51:44 -06:00
kprobes.txt docs: kprobes.txt: Fix whitespacing 2017-07-14 13:58:14 -06:00
kref.txt kref.txt: standardize document format 2017-07-14 13:51:45 -06:00
ldm.txt ldm.txt: standardize document format 2017-07-14 13:51:45 -06:00
lockup-watchdogs.txt lockup-watchdogs.txt: standardize document format 2017-07-14 13:51:46 -06:00
logo.gif
logo.txt
lsm.txt docs-rst: convert lsm from DocBook to ReST 2017-05-16 08:44:19 -03:00
lzo.txt lzo.txt: standardize document format 2017-07-14 13:51:46 -06:00
mailbox.txt mailbox.txt: standardize document format 2017-07-14 13:51:47 -06:00
Makefile docs: remove DocBook from the building system 2017-05-16 08:44:19 -03:00
memory-barriers.txt A set of fixes for various warnings, including the one caused by the 2017-07-13 13:44:54 -07:00
memory-hotplug.txt memory-hotplug.txt: standardize document format 2017-07-14 13:57:53 -06:00
men-chameleon-bus.txt men-chameleon-bus.txt: standardize document format 2017-07-14 13:57:54 -06:00
nommu-mmap.txt nommu-mmap.txt: don't use all upper case on titles 2017-07-14 13:57:55 -06:00
ntb.txt This series converts a number of top-level documents to the RST format 2017-07-15 12:58:58 -07:00
numastat.txt numastat.txt: standardize document format 2017-07-14 13:57:56 -06:00
padata.txt padata.txt: standardize document format 2017-07-14 13:57:56 -06:00
parport-lowlevel.txt parport-lowlevel.txt: standardize document format 2017-07-14 13:57:57 -06:00
percpu-rw-semaphore.txt percpu-rw-semaphore.txt: standardize document format 2017-07-14 13:57:58 -06:00
phy.txt phy.txt: standardize document format 2017-07-14 13:57:58 -06:00
pi-futex.txt pi-futex.txt: standardize document format 2017-07-14 13:57:59 -06:00
pnp.txt pnp.txt: standardize document format 2017-07-14 13:57:59 -06:00
preempt-locking.txt preempt-locking.txt: standardize document format 2017-07-14 13:58:00 -06:00
printk-formats.txt printk-formats.txt: standardize document format 2017-07-14 13:58:00 -06:00
pwm.txt pwm: Standardize document format 2017-07-06 08:23:30 +02:00
rbtree.txt rbtree.txt: standardize document format 2017-07-14 13:58:01 -06:00
remoteproc.txt remoteproc.txt: standardize document format 2017-07-14 13:58:02 -06:00
rfkill.txt rfkill.txt: standardize document format 2017-07-14 13:58:02 -06:00
robust-futex-ABI.txt robust-futex-ABI.txt: standardize document format 2017-07-14 13:58:03 -06:00
robust-futexes.txt robust-futexes.txt: standardize document format 2017-07-14 13:58:03 -06:00
rpmsg.txt rpmsg.txt: standardize document format 2017-07-14 13:58:04 -06:00
rtc.txt rtc: add generic nvmem support 2017-07-07 13:14:14 +02:00
SAK.txt SAK.txt: standardize document format 2017-07-14 13:58:04 -06:00
sgi-ioc4.txt sgi-ioc4.txt: standardize document format 2017-07-14 13:58:05 -06:00
siphash.txt siphash.txt: standardize document format 2017-07-14 13:58:06 -06:00
SM501.txt SM501.txt: standardize document format 2017-07-14 13:58:06 -06:00
smsc_ece1099.txt smsc_ece1099.txt: standardize document format 2017-07-14 13:58:07 -06:00
static-keys.txt static-keys.txt: standardize document format 2017-07-14 13:58:07 -06:00
SubmittingPatches
svga.txt svga.txt: standardize document format 2017-07-14 13:58:08 -06:00
switchtec.txt switchtec: Add IOCTLs to the Switchtec driver 2017-04-12 12:23:37 -05:00
sync_file.txt sync_file.txt: standardize document format 2017-05-24 13:01:27 -03:00
tee.txt tee.txt: standardize document format 2017-07-14 13:58:14 -06:00
this_cpu_ops.txt this_cpu_ops.txt: standardize document format 2017-07-14 13:58:08 -06:00
unaligned-memory-access.txt unaligned-memory-access.txt: standardize document format 2017-07-14 13:58:09 -06:00
vfio-mediated-device.txt vfio-mediated-device.txt: standardize document format 2017-07-14 13:58:10 -06:00
vfio.txt vfio.txt: standardize document format 2017-07-14 13:58:10 -06:00
video-output.txt
xillybus.txt xillybus.txt: standardize document format 2017-07-14 13:58:11 -06:00
xz.txt xz.txt: standardize document format 2017-07-14 13:58:11 -06:00
zorro.txt zorro.txt: standardize document format 2017-07-14 13:58:12 -06:00