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Ingo Molnar
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Merge branch 'tip/perf/core' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace into perf/core
2 parents 79e406d + 57c072c commit 3aabae7

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‎Documentation/DocBook/device-drivers.tmpl‎

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<sect1><title>Atomic and pointer manipulation</title>
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!Iarch/x86/include/asm/atomic.h
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!Iarch/x86/include/asm/unaligned.h
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</sect1>
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<sect1><title>Delaying, scheduling, and timer routines</title>

‎Documentation/DocBook/kernel-api.tmpl‎

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</para>
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<sect1><title>String Conversions</title>
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!Ilib/vsprintf.c
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!Elib/vsprintf.c
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</sect1>
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<sect1><title>String Manipulation</title>

‎Documentation/DocBook/kernel-locking.tmpl‎

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</sect1>
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</chapter>
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<chapter id="apiref">
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<title>Mutex API reference</title>
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!Iinclude/linux/mutex.h
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!Ekernel/mutex.c
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</chapter>
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<chapter id="references">
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<title>Further reading</title>
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‎Documentation/DocBook/tracepoint.tmpl‎

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<title>Block IO</title>
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!Iinclude/trace/events/block.h
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</chapter>
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<chapter id="workqueue">
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<title>Workqueue</title>
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!Iinclude/trace/events/workqueue.h
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</chapter>
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</book>

‎Documentation/block/cfq-iosched.txt‎

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CFQ ioscheduler tunables
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========================
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slice_idle
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----------
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This specifies how long CFQ should idle for next request on certain cfq queues
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(for sequential workloads) and service trees (for random workloads) before
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queue is expired and CFQ selects next queue to dispatch from.
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By default slice_idle is a non-zero value. That means by default we idle on
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queues/service trees. This can be very helpful on highly seeky media like
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single spindle SATA/SAS disks where we can cut down on overall number of
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seeks and see improved throughput.
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Setting slice_idle to 0 will remove all the idling on queues/service tree
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level and one should see an overall improved throughput on faster storage
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devices like multiple SATA/SAS disks in hardware RAID configuration. The down
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side is that isolation provided from WRITES also goes down and notion of
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IO priority becomes weaker.
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So depending on storage and workload, it might be useful to set slice_idle=0.
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In general I think for SATA/SAS disks and software RAID of SATA/SAS disks
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keeping slice_idle enabled should be useful. For any configurations where
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there are multiple spindles behind single LUN (Host based hardware RAID
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controller or for storage arrays), setting slice_idle=0 might end up in better
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throughput and acceptable latencies.
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CFQ IOPS Mode for group scheduling
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===================================
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Basic CFQ design is to provide priority based time slices. Higher priority
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process gets bigger time slice and lower priority process gets smaller time
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slice. Measuring time becomes harder if storage is fast and supports NCQ and
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it would be better to dispatch multiple requests from multiple cfq queues in
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request queue at a time. In such scenario, it is not possible to measure time
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consumed by single queue accurately.
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What is possible though is to measure number of requests dispatched from a
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single queue and also allow dispatch from multiple cfq queue at the same time.
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This effectively becomes the fairness in terms of IOPS (IO operations per
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second).
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If one sets slice_idle=0 and if storage supports NCQ, CFQ internally switches
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to IOPS mode and starts providing fairness in terms of number of requests
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dispatched. Note that this mode switching takes effect only for group
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scheduling. For non-cgroup users nothing should change.

‎Documentation/cgroups/blkio-controller.txt‎

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CFQ sysfs tunable
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=================
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/sys/block/<disk>/queue/iosched/group_isolation
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-----------------------------------------------
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If group_isolation=1, it provides stronger isolation between groups at the
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expense of throughput. By default group_isolation is 0. In general that
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and one wants stronger isolation between groups, then set group_isolation=1
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but this will come at cost of reduced throughput.
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/sys/block/<disk>/queue/iosched/slice_idle
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------------------------------------------
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On a faster hardware CFQ can be slow, especially with sequential workload.
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This happens because CFQ idles on a single queue and single queue might not
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drive deeper request queue depths to keep the storage busy. In such scenarios
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one can try setting slice_idle=0 and that would switch CFQ to IOPS
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(IO operations per second) mode on NCQ supporting hardware.
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That means CFQ will not idle between cfq queues of a cfq group and hence be
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able to driver higher queue depth and achieve better throughput. That also
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means that cfq provides fairness among groups in terms of IOPS and not in
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terms of disk time.
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/sys/block/<disk>/queue/iosched/group_idle
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------------------------------------------
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If one disables idling on individual cfq queues and cfq service trees by
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setting slice_idle=0, group_idle kicks in. That means CFQ will still idle
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on the group in an attempt to provide fairness among groups.
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By default group_idle is same as slice_idle and does not do anything if
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slice_idle is enabled.
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One can experience an overall throughput drop if you have created multiple
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groups and put applications in that group which are not driving enough
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IO to keep disk busy. In that case set group_idle=0, and CFQ will not idle
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on individual groups and throughput should improve.
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What works
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==========
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- Currently only sync IO queues are support. All the buffered writes are

‎Documentation/gpio.txt‎

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If you want to initialize a structure with an invalid GPIO number, use
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some negative number (perhaps "-EINVAL"); that will never be valid. To
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test if a number could reference a GPIO, you may use this predicate:
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test if such number from such a structure could reference a GPIO, you
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may use this predicate:
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int gpio_is_valid(int number);
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A number that's not valid will be rejected by calls which may request
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or free GPIOs (see below). Other numbers may also be rejected; for
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example, a number might be valid but unused on a given board.
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Whether a platform supports multiple GPIO controllers is currently a
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platform-specific implementation issue.
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example, a number might be valid but temporarily unused on a given board.
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Whether a platform supports multiple GPIO controllers is a platform-specific
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implementation issue, as are whether that support can leave "holes" in the space
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of GPIO numbers, and whether new controllers can be added at runtime. Such issues
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can affect things including whether adjacent GPIO numbers are both valid.
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Using GPIOs
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-----------
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ARCH_REQUIRE_GPIOLIB or ARCH_WANT_OPTIONAL_GPIOLIB
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and arrange that its <asm/gpio.h> includes <asm-generic/gpio.h> and defines
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three functions: gpio_get_value(), gpio_set_value(), and gpio_cansleep().
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They may also want to provide a custom value for ARCH_NR_GPIOS.
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ARCH_REQUIRE_GPIOLIB means that the gpio-lib code will always get compiled
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It may also provide a custom value for ARCH_NR_GPIOS, so that it better
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reflects the number of GPIOs in actual use on that platform, without
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wasting static table space. (It should count both built-in/SoC GPIOs and
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also ones on GPIO expanders.
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ARCH_REQUIRE_GPIOLIB means that the gpiolib code will always get compiled
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into the kernel on that architecture.
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ARCH_WANT_OPTIONAL_GPIOLIB means the gpio-lib code defaults to off and the user
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ARCH_WANT_OPTIONAL_GPIOLIB means the gpiolib code defaults to off and the user
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can enable it and build it into the kernel optionally.
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If neither of these options are selected, the platform does not support

‎Documentation/kernel-doc-nano-HOWTO.txt‎

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section titled <section title> from <filename>.
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Spaces are allowed in <section title>; do not quote the <section title>.
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!C<filename> is replaced by nothing, but makes the tools check that
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all DOC: sections and documented functions, symbols, etc. are used.
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This makes sense to use when you use !F/!P only and want to verify
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that all documentation is included.
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Tim.
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*/ <twaugh@redhat.com>

‎Documentation/kernel-parameters.txt‎

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force Enable ASPM even on devices that claim not to support it.
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WARNING: Forcing ASPM on may cause system lockups.
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pcie_ports= [PCIE] PCIe ports handling:
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auto Ask the BIOS whether or not to use native PCIe services
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associated with PCIe ports (PME, hot-plug, AER). Use
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them only if that is allowed by the BIOS.
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native Use native PCIe services associated with PCIe ports
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unconditionally.
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compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
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ports driver.
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pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
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Format: {auto|force}[,nomsi]
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auto Use native PCIe PME signaling if the BIOS allows the
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kernel to control PCIe config registers of root ports.
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force Use native PCIe PME signaling even if the BIOS refuses
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to allow the kernel to control the relevant PCIe config
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registers.
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nomsi Do not use MSI for native PCIe PME signaling (this makes
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all PCIe root ports use INTx for everything).
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all PCIe root ports use INTx for all services).
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pcmv= [HW,PCMCIA] BadgePAD 4
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‎Documentation/lguest/Makefile‎

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# This creates the demonstration utility "lguest" which runs a Linux guest.
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CFLAGS:=-m32 -Wall -Wmissing-declarations -Wmissing-prototypes -O3 -I../../include -I../../arch/x86/include -U_FORTIFY_SOURCE
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# Missing headers? Add "-I../../include -I../../arch/x86/include"
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CFLAGS:=-m32 -Wall -Wmissing-declarations -Wmissing-prototypes -O3 -U_FORTIFY_SOURCE
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all: lguest
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