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David Rientjes 2da02997e0 mm: add dirty_background_bytes and dirty_bytes sysctls 
This change introduces two new sysctls to /proc/sys/vm:
dirty_background_bytes and dirty_bytes.

dirty_background_bytes is the counterpart to dirty_background_ratio and
dirty_bytes is the counterpart to dirty_ratio.

With growing memory capacities of individual machines, it's no longer
sufficient to specify dirty thresholds as a percentage of the amount of
dirtyable memory over the entire system.

dirty_background_bytes and dirty_bytes specify quantities of memory, in
bytes, that represent the dirty limits for the entire system.  If either
of these values is set, its value represents the amount of dirty memory
that is needed to commence either background or direct writeback.

When a `bytes' or `ratio' file is written, its counterpart becomes a
function of the written value.  For example, if dirty_bytes is written to
be 8096, 8K of memory is required to commence direct writeback.
dirty_ratio is then functionally equivalent to 8K / the amount of
dirtyable memory:

	dirtyable_memory = free pages + mapped pages + file cache

	dirty_background_bytes = dirty_background_ratio * dirtyable_memory
		-or-
	dirty_background_ratio = dirty_background_bytes / dirtyable_memory

		AND

	dirty_bytes = dirty_ratio * dirtyable_memory
		-or-
	dirty_ratio = dirty_bytes / dirtyable_memory

Only one of dirty_background_bytes and dirty_background_ratio may be
specified at a time, and only one of dirty_bytes and dirty_ratio may be
specified.  When one sysctl is written, the other appears as 0 when read.

The `bytes' files operate on a page size granularity since dirty limits
are compared with ZVC values, which are in page units.

Prior to this change, the minimum dirty_ratio was 5 as implemented by
get_dirty_limits() although /proc/sys/vm/dirty_ratio would show any user
written value between 0 and 100.  This restriction is maintained, but
dirty_bytes has a lower limit of only one page.

Also prior to this change, the dirty_background_ratio could not equal or
exceed dirty_ratio.  This restriction is maintained in addition to
restricting dirty_background_bytes.  If either background threshold equals
or exceeds that of the dirty threshold, it is implicitly set to half the
dirty threshold.

Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Andrea Righi <righi.andrea@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-06 15:59:03 -08:00
..
ABI mm: show node to memory section relationship with symlinks in sysfs 2009-01-06 15:59:00 -08:00
accounting .gitignore updates 2008-10-30 11:38:45 -07:00
acpi ACPI: update debug parameter documentation 2008-11-07 21:45:29 -05:00
aoe aoe: user can ask driver to forget previously detected devices 2008-02-08 09:22:31 -08:00
arm Merge branch 'for-rmk' of git://git.kernel.org/pub/scm/linux/kernel/git/ycmiao/pxa-linux-2.6 into devel 2008-12-29 18:08:11 +00:00
auxdisplay .gitignore updates 2008-10-30 11:38:45 -07:00
blackfin Blackfin arch: add supporting for kgdb 2008-10-13 14:07:19 +08:00
block Documentation: remove reference to ll_rw_blk.c and moved drivers/block/elevator.c 2008-12-29 08:28:43 +01:00
blockdev Create/use more directory structure in the Documentation/ tree. 2008-11-14 17:28:53 +00:00
cdrom doc/cdrom: Trvial documentation error, file not present 2008-10-10 08:22:44 +02:00
cgroups freezer_cg: disable writing freezer.state of root cgroup 2008-11-12 17:17:16 -08:00
connector .gitignore updates 2008-10-30 11:38:45 -07:00
console
controllers sched: add hierarchical accounting to cpu accounting controller 2008-11-11 12:13:28 +01:00
cpu-freq doc: Update sh cpufreq documentation. 2008-12-22 18:44:47 +09:00
cpuidle cpuidle: Add Documentation 2008-02-14 00:16:13 -05:00
cris fix random typos 2008-10-16 11:21:30 -07:00
crypto
development-process Add the development process document 2008-10-16 11:51:30 -06:00
device-mapper dm crypt: add documentation 2008-04-25 13:27:03 +01:00
DocBook WAN: syncppp.c is no longer used by any kernel code. Remove it. 2008-11-22 02:49:48 +01:00
driver-model Driver core: Update some prototypes in platform.txt 2008-02-02 15:14:49 -08:00
dvb V4L/DVB (9812): [PATCH] short help for Technisat cards to select the right configuration 2008-12-30 09:38:35 -02:00
early-userspace Documentation: Remove last references to BitKeeper. 2008-04-21 22:19:05 +00:00
fault-injection
fb [ARM] pxafb: add support for overlay1 and overlay2 as framebuffer devices 2008-12-29 18:00:04 +08:00
filesystems mm: add dirty_background_bytes and dirty_bytes sysctls 2009-01-06 15:59:03 -08:00
firmware_class firmware_sample_driver.c: fix coding style 2008-04-21 22:23:30 +00:00
frv move frv docs one level up 2008-02-03 15:54:28 +02:00
hwmon adt7462: new hwmon driver 2008-11-12 17:17:17 -08:00
i2c i2c: The i2c mailing list is moving 2008-10-30 15:55:47 +01:00
i2o
ia64 .gitignore updates 2008-10-30 11:38:45 -07:00
ide gayle: add "doubler" parameter 2008-04-27 15:38:30 +02:00
infiniband
input Input: fix the example of an input device driver 2008-11-11 11:41:49 -05:00
ioctl UBI: document UBI ioctls 2008-12-09 15:59:07 +02:00
isdn Rationalise Randy's address a bit 2008-10-30 11:38:47 -07:00
ja_JP HOWTO: Sync patch for jp_JP/HOWTO 2008-10-29 15:03:50 -07:00
kbuild kbuild: document environment variables 2009-01-02 20:43:25 +01:00
kdump powerpc: Support for relocatable kdump kernel 2008-10-22 15:01:22 +11:00
ko_KR
laptops Merge branch 'linus' into test 2008-10-23 00:11:07 -04:00
lguest lguest: move the initial guest page table creation code to the host 2008-12-30 09:26:11 +10:30
m68k
make
mips au1xxx-ide: fix MWDMA support 2008-04-26 22:25:22 +02:00
mn10300 mn10300: add the MN10300/AM33 architecture to the kernel 2008-02-08 09:22:30 -08:00
mtd [MTD] [NAND] nand_ecc.c: rewrite for improved performance 2008-08-16 10:55:33 +01:00
namespaces
netlabel
networking dccp ccid-2: Phase out the use of boolean Ack Vector sysctl 2008-12-08 01:19:06 -08:00
parisc
PCI Create/use more directory structure in the Documentation/ tree. 2008-11-14 17:28:53 +00:00
pcmcia .gitignore updates 2008-10-30 11:38:45 -07:00
power pm: document use of RTC in pm_trace 2008-10-16 11:21:29 -07:00
powerpc gianfar: Convert gianfar to an of_platform_driver 2008-12-16 15:29:15 -08:00
prctl generic, x86: add tests for prctl PR_GET_TSC and PR_SET_TSC 2008-04-19 19:19:55 +02:00
RCU Merge branch 'core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2008-12-30 16:10:19 -08:00
s390 [S390] cio: Exorcise cio_msg= from documentation. 2008-10-10 21:33:49 +02:00
scheduler Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2008-12-28 12:27:58 -08:00
scsi [SCSI] cxgb3i: Add cxgb3i iSCSI driver. 2008-12-30 10:45:33 -06:00
serial Create/use more directory structure in the Documentation/ tree. 2008-11-14 17:28:53 +00:00
sh sh: Kill off remaining CONFIG_SH_KGDB bits. 2008-12-22 18:44:05 +09:00
sound Merge branch 'topic/oxygen' into to-push 2008-12-25 11:40:30 +01:00
sparc sparc: Remove Documentation/sparc/sbus_drivers.txt 2008-08-29 02:15:25 -07:00
spi spi documentation: use __initdata on struct 2008-12-01 19:55:24 -08:00
sysctl mm: add dirty_background_bytes and dirty_bytes sysctls 2009-01-06 15:59:03 -08:00
telephony remove mention of CONFIG_KMOD from documentation 2008-07-22 19:24:29 +10:00
thermal thermal: update the documentation 2008-04-29 02:49:47 -04:00
timers hpet: /dev/hpet - fixes and cleanup 2008-07-31 18:45:41 +02:00
tracers tracing, doc: update mmiotrace documentation 2008-11-23 20:33:24 +01:00
uml
usb Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6 into for-upstream 2009-01-02 13:17:13 +00:00
video4linux V4L/DVB (10157): Add USB ID for the Sil4701 radio from DealExtreme 2009-01-02 17:13:56 -02:00
vm .gitignore updates 2008-10-30 11:38:45 -07:00
w1 hdq: documentation for OMAP HDQ 2008-11-12 17:17:18 -08:00
watchdog .gitignore updates 2008-10-30 11:38:45 -07:00
x86 Merge branches 'x86/apic', 'x86/cleanups', 'x86/cpufeature', 'x86/crashdump', 'x86/debug', 'x86/defconfig', 'x86/detect-hyper', 'x86/doc', 'x86/dumpstack', 'x86/early-printk', 'x86/fpu', 'x86/idle', 'x86/io', 'x86/memory-corruption-check', 'x86/microcode', 'x86/mm', 'x86/mtrr', 'x86/nmi-watchdog', 'x86/pat2', 'x86/pci-ioapic-boot-irq-quirks', 'x86/ptrace', 'x86/quirks', 'x86/reboot', 'x86/setup-memory', 'x86/signal', 'x86/sparse-fixes', 'x86/time', 'x86/uv' and 'x86/xen' into x86/core 2008-12-23 16:27:23 +01:00
zh_CN
00-INDEX Merge branch 'doc-subdirs' of git://git.kernel.org/pub/scm/linux/kernel/git/rdunlap/linux-docs 2008-11-15 11:51:03 -08:00
applying-patches.txt
atomic_ops.txt documentation: atomic_add_unless() doesn't imply mb() on failure 2008-02-23 17:52:36 -08:00
basic_profiling.txt
binfmt_misc.txt
braille-console.txt Basic braille screen reader support 2008-04-30 08:29:52 -07:00
bt8xxgpio.txt gpio: add bt8xxgpio driver 2008-07-25 10:53:30 -07:00
BUG-HUNTING Documentation: add hint about call traces & module symbols to BUG-HUNTING 2008-02-06 10:41:09 -08:00
c2port.txt Add c2 port support 2008-11-12 17:17:18 -08:00
cachetlb.txt
Changes
CodingStyle documentation: update CodingStyle tips for Emacs users 2008-07-25 10:53:29 -07:00
cpu-hotplug.txt x86: use possible_cpus=NUM to extend the possible cpus allowed 2008-12-18 12:08:05 +01:00
cpu-load.txt
cpusets.txt container freezer: document the cgroup freezer subsystem. 2008-10-20 08:52:34 -07:00
cputopology.txt sysfs: add documentation to cputopology.txt for system cpumasks 2008-12-19 17:47:12 +10:30
credentials.txt CRED: Documentation 2008-11-14 10:39:26 +11:00
dcdbas.txt
debugging-modules.txt Documentation: Clarify when module debugging actually works. 2008-02-03 15:27:38 +02:00
debugging-via-ohci1394.txt firewire: fw-ohci: add option for remote debugging 2008-04-18 17:55:33 +02:00
dell_rbu.txt
devices.txt USB: add USB test and measurement class driver 2008-10-17 14:40:51 -07:00
DMA-API.txt DMA-API.txt: fix description of pci_map_sg/dma_map_sg scatterlists handling 2008-12-01 19:55:24 -08:00
DMA-attributes.txt powerpc/cell: Add DMA_ATTR_WEAK_ORDERING dma attribute and use in Cell IOMMU code 2008-07-22 10:39:36 +10:00
DMA-ISA-LPC.txt
DMA-mapping.txt Documentation/DMA-mapping.txt: update for pci_dma_mapping_error() changes 2008-09-23 08:09:14 -07:00
dontdiff dontdiff: more updates to be closer to gitignore 2008-10-16 11:21:31 -07:00
edac.txt Documentation cleanup: trivial misspelling, punctuation, and grammar corrections. 2008-07-26 12:00:06 -07:00
eisa.txt
email-clients.txt Documentation/email-clients.txt: add some info about gmail 2008-11-06 15:41:19 -08:00
exception.txt
feature-removal-schedule.txt remove ide-scsi 2009-01-02 16:12:51 +01:00
ftrace.txt ftrace: improve documentation 2008-11-28 13:15:14 +01:00
gpio.txt gpiolib: request/free hooks 2008-10-16 11:21:40 -07:00
highuid.txt [SPARC]: Remove SunOS and Solaris binary support. 2008-04-21 15:10:15 -07:00
HOWTO Remove Andrew Morton's http://www.zip.com.au/~akpm/ 2008-10-16 11:21:32 -07:00
hw_random.txt hw_random doc updates 2008-03-24 19:22:19 -07:00
ics932s401 ics932s401: new clock generator chip driver 2008-11-12 17:17:18 -08:00
initrd.txt use the newc archive format as requested by initramfs 2008-02-03 14:54:41 +02:00
Intel-IOMMU.txt Documentation cleanup: trivial misspelling, punctuation, and grammar corrections. 2008-07-26 12:00:06 -07:00
io-mapping.txt io mapping: improve documentation 2008-11-03 18:21:44 +01:00
IO-mapping.txt
io_ordering.txt
iostats.txt Documentation cleanup: trivial misspelling, punctuation, and grammar corrections. 2008-07-26 12:00:06 -07:00
IPMI.txt
IRQ-affinity.txt genirq: Expose default irq affinity mask (take 3) 2008-06-05 15:18:30 +02:00
IRQ.txt
irqflags-tracing.txt
isapnp.txt
java.txt
kernel-doc-nano-HOWTO.txt sched: add kernel doc for the completion, fix kernel-doc-nano-HOWTO.txt 2008-08-26 10:26:54 +02:00
kernel-docs.txt doc: update to URL and status of kernel-docs.txt entry 2008-06-06 11:29:10 -07:00
kernel-parameters.txt Merge branch 'for-linus' of git://git390.osdl.marist.edu/pub/scm/linux-2.6 2008-12-28 12:33:21 -08:00
keys-request-key.txt keys: allow the callout data to be passed as a blob rather than a string 2008-04-29 08:06:16 -07:00
keys.txt Documentation cleanup: trivial misspelling, punctuation, and grammar corrections. 2008-07-26 12:00:06 -07:00
kobject.txt kobject: Fix kobject_rename and !CONFIG_SYSFS 2008-10-16 09:24:52 -07:00
kprobes.txt powerpc/booke: Add kprobes support for booke style processors 2008-06-26 03:35:46 -05:00
kref.txt docs: convert kref semaphore to mutex 2008-02-06 10:41:09 -08:00
ldm.txt
leds-class.txt Documentation cleanup: trivial misspelling, punctuation, and grammar corrections. 2008-07-26 12:00:06 -07:00
local_ops.txt documentation: local_ops fix on_each_cpu 2008-12-01 13:51:26 +01:00
lockdep-design.txt
lockstat.txt lockstat: contend with points 2008-10-20 15:43:10 +02:00
logo.gif
logo.txt
magic-number.txt [SPARC]: Remove SunOS and Solaris binary support. 2008-04-21 15:10:15 -07:00
Makefile docsrc: build Documentation/ sources 2008-08-12 16:07:30 -07:00
ManagementStyle docs: fix ManagementStyle book name 2008-10-30 11:38:46 -07:00
markers.txt markers: comment marker_synchronize_unregister() on data dependency 2008-11-28 16:47:41 +01:00
mca.txt The ps2esdi driver was marked as BROKEN more than two years ago due to being 2008-03-17 09:03:05 +01:00
md.txt md: Tidy up rdev_size_store a bit: 2008-07-21 14:22:18 +10:00
memory-barriers.txt read_barrier_depends arch fixlets 2008-05-14 10:05:18 -07:00
memory-hotplug.txt mm: show node to memory section relationship with symlinks in sysfs 2009-01-06 15:59:00 -08:00
memory.txt
mono.txt
mutex-design.txt
nmi_watchdog.txt x86, nmi-watchdog: update procfs nmi_watchdog file documentation v2 2008-10-30 19:07:04 +01:00
nommu-mmap.txt
numastat.txt
oops-tracing.txt Taint kernel after WARN_ON(condition) 2008-04-29 08:05:59 -07:00
parport-lowlevel.txt
parport.txt
pi-futex.txt
pnp.txt
preempt-locking.txt
printk-formats.txt DOC: add printk-formats.txt 2008-11-12 17:17:17 -08:00
prio_tree.txt
rbtree.txt
rfkill.txt rfkill: add master_switch_mode and EPO lock to rfkill and rfkill-input 2008-10-31 19:00:09 -04:00
robust-futex-ABI.txt
robust-futexes.txt
rt-mutex-design.txt
rt-mutex.txt
rtc.txt rtc: cleanup example code 2008-02-06 10:41:14 -08:00
SAK.txt Remove Andrew Morton's old email accounts 2008-10-16 11:21:32 -07:00
SecurityBugs
SELinux.txt selinux: add support for installing a dummy policy (v2) 2008-08-27 08:54:08 +10:00
serial-console.txt
sgi-ioc4.txt
sgi-visws.txt
SM501.txt
Smack.txt Smack: Simplified Mandatory Access Control Kernel 2008-02-05 09:44:20 -08:00
sparse.txt kbuild: sparse needs CF not CHECKFLAGS 2008-07-25 22:12:39 +02:00
spinlocks.txt Add additional examples in Documentation/spinlocks.txt 2008-04-11 13:21:14 -06:00
stable_api_nonsense.txt
stable_kernel_rules.txt Update stable tree documentation 2008-10-29 15:03:49 -07:00
SubmitChecklist documentation: explain memory barriers 2008-10-16 11:21:32 -07:00
SubmittingDrivers Remove Andrew Morton's old email accounts 2008-10-16 11:21:32 -07:00
SubmittingPatches Merge branch 'docs' of git://git.lwn.net/linux-2.6 2008-10-16 12:18:16 -07:00
svga.txt
sysfs-rules.txt sysfs-rules.txt: reword API stability statement 2008-07-21 21:54:59 -07:00
sysrq.txt Merge branch 'v28-timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2008-10-20 13:19:56 -07:00
tracepoints.txt tracepoints: Documentation TPPROTO misspelt in Documentation/tracepoints.txt 2008-11-29 15:13:42 +01:00
unaligned-memory-access.txt introduce HAVE_EFFICIENT_UNALIGNED_ACCESS Kconfig symbol 2008-07-25 10:53:27 -07:00
unicode.txt
unshare.txt
VGA-softcursor.txt
video-output.txt
volatile-considered-harmful.txt Documentation cleanup: trivial misspelling, punctuation, and grammar corrections. 2008-07-26 12:00:06 -07:00
voyager.txt
zorro.txt