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Sebastian Andrzej Siewior 98e696a272 sched/rt: Don't try push tasks if there are none. 
I have a RT task X at a high priority and cyclictest on each CPU with
lower priority than X's. If X is active and each CPU wakes their own
cylictest thread then it ends in a longer rto_push storm.
A random CPU determines via balance_rt() that the CPU on which X is
running needs to push tasks. X has the highest priority, cyclictest is
next in line so there is nothing that can be done since the task with
the higher priority is not touched.

tell_cpu_to_push() increments rto_loop_next and schedules
rto_push_irq_work_func() on X's CPU. The other CPUs also increment the
loop counter and do the same. Once rto_push_irq_work_func() is active it
does nothing because it has _no_ pushable tasks on its runqueue. Then
checks rto_next_cpu() and decides to queue irq_work on the local CPU
because another CPU requested a push by incrementing the counter.

I have traces where ~30 CPUs request this ~3 times each before it
finally ends. This greatly increases X's runtime while X isn't making
much progress.

Teach rto_next_cpu() to only return CPUs which also have tasks on their
runqueue which can be pushed away. This does not reduce the
tell_cpu_to_push() invocations (rto_loop_next counter increments) but
reduces the amount of issued rto_push_irq_work_func() if nothing can be
done. As the result the overloaded CPU is blocked less often.

There are still cases where the "same job" is repeated several times
(for instance the current CPU needs to resched but didn't yet because
the irq-work is repeated a few times and so the old task remains on the
CPU) but the majority of request end in tell_cpu_to_push() before an IPI
is issued.

Reviewed-by: "Steven Rostedt (Google)" <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20230801152648._y603AS_@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2024-12-03 21:45:38 +01:00
.github/workflows
android
arch powerpc/powernv: Free name on error in opal_event_init() 2024-11-30 02:33:27 +01:00
block Revert "block: remove the blk_flush_integrity call in blk_integrity_unregister" 2024-11-24 00:23:47 +01:00
certs
crypto crypto: aead,cipher - zeroize key buffer after use 2024-11-19 14:19:40 +01:00
Documentation Revert "arm64: cpufeature: Fix the visibility of compat hwcaps" 2024-11-24 00:23:54 +01:00
drivers md/raid10: improve code of mrdev in raid10_sync_request 2024-11-30 02:33:28 +01:00
firmware/tsp_goodix
fs fs: Fix uninitialized value issue in from_kuid and from_kgid 2024-11-30 02:33:28 +01:00
gki
include trace: add CONFIG_DISABLE_TRACE_PRINTK option 2024-12-03 21:45:24 +01:00
init kernel/sys.c: implement custom uname override 2024-11-19 17:55:01 +01:00
io_uring io_uring: fix possible deadlock in io_register_iowq_max_workers() 2024-11-30 02:33:28 +01:00
ipc Make more sysctl constants read-only 2024-11-30 02:15:48 +01:00
kernel sched/rt: Don't try push tasks if there are none. 2024-12-03 21:45:38 +01:00
kernel_build kernel_build: build-ksu.sh: Switch up to a newer clang 2024-11-30 03:37:29 +01:00
KernelSU@b766b98513 Added KernelSU 2024-11-19 23:08:59 +01:00
kunitconfigs
lib Make more sysctl constants read-only 2024-11-30 02:15:48 +01:00
LICENSES
mm bug on cache_from_obj !PageSlab check 2024-11-30 02:17:27 +01:00
net 9p: fix slab cache name creation for real 2024-11-30 02:33:28 +01:00
samples Add gitignore file for samples/fanotify/ subdirectory 2024-11-23 23:20:30 +01:00
scripts stop using git tags for LOCALVERSION 2024-11-30 02:17:39 +01:00
security security/keys: fix slab-out-of-bounds in key_task_permission 2024-11-30 02:33:21 +01:00
sound sound: Make CONFIG_SND depend on INDIRECT_IOMEM instead of UML 2024-11-30 02:33:27 +01:00
test
tools perf session: Add missing evlist__delete when deleting a session 2024-11-30 02:33:26 +01:00
usr
virt Revert "KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin()" 2024-11-24 00:22:53 +01:00
build.config.aarch64
build.config.allmodconfig
build.config.allmodconfig.aarch64
build.config.allmodconfig.arm
build.config.allmodconfig.x86_64
build.config.amlogic
build.config.arm
build.config.common
build.config.db845c
build.config.erd8825_a25_s
build.config.erd8825_s
build.config.erd9925_evt0_s
build.config.erd9925_evt0_s5300_s
build.config.erd9925_s
build.config.gki
build.config.gki-debug.aarch64
build.config.gki-debug.x86_64
build.config.gki.aarch64
build.config.gki.aarch64.fips140
build.config.gki.aarch64.fips140_eval_testing
build.config.gki.x86_64
build.config.gki_kasan
build.config.gki_kasan.aarch64
build.config.gki_kasan.x86_64
build.config.gki_kprobes
build.config.gki_kprobes.aarch64
build.config.gki_kprobes.x86_64
build.config.hikey960
build.config.khwasan
build.config.mcd
build.config.rockchip
build.config.universal2100_s
build.config.universal8825_s
build.config.universal9925_evt0_s
build.config.universal9925_s
build.config.x86_64
build.sh build.sh: Fixup 2024-12-03 18:20:19 +01:00
COPYING
CREDITS
Kbuild
Kconfig
linux-stable.sh
MAINTAINERS
Makefile Linux 5.10.230 2024-11-30 02:33:28 +01:00
OWNERS
README
README.md
vendor_boot_module_order_exynos2100.cfg
vendor_boot_module_order_s5e8825.cfg
vendor_boot_module_order_s5e9925.cfg
vendor_module_list_s5e8825.cfg
vendor_module_list_s5e9925.cfg
vendor_module_list_s5e9925_b0s.cfg
vendor_module_list_s5e9925_g0s.cfg
vendor_module_list_s5e9925_r0s.cfg

README.md

How do I submit patches to Android Common Kernels

  1. BEST: Make all of your changes to upstream Linux. If appropriate, backport to the stable releases. These patches will be merged automatically in the corresponding common kernels. If the patch is already in upstream Linux, post a backport of the patch that conforms to the patch requirements below.

    • Do not send patches upstream that contain only symbol exports. To be considered for upstream Linux, additions of EXPORT_SYMBOL_GPL() require an in-tree modular driver that uses the symbol -- so include the new driver or changes to an existing driver in the same patchset as the export.
    • When sending patches upstream, the commit message must contain a clear case for why the patch is needed and beneficial to the community. Enabling out-of-tree drivers or functionality is not not a persuasive case.

  2. LESS GOOD: Develop your patches out-of-tree (from an upstream Linux point-of-view). Unless these are fixing an Android-specific bug, these are very unlikely to be accepted unless they have been coordinated with kernel-team@android.com. If you want to proceed, post a patch that conforms to the patch requirements below.

Common Kernel patch requirements

  • All patches must conform to the Linux kernel coding standards and pass script/checkpatch.pl
  • Patches shall not break gki_defconfig or allmodconfig builds for arm, arm64, x86, x86_64 architectures (see https://source.android.com/setup/build/building-kernels)
  • If the patch is not merged from an upstream branch, the subject must be tagged with the type of patch: UPSTREAM:, BACKPORT:, FROMGIT:, FROMLIST:, or ANDROID:.
  • All patches must have a Change-Id: tag (see https://gerrit-review.googlesource.com/Documentation/user-changeid.html)
  • If an Android bug has been assigned, there must be a Bug: tag.
  • All patches must have a Signed-off-by: tag by the author and the submitter

Additional requirements are listed below based on patch type

Requirements for backports from mainline Linux: UPSTREAM:, BACKPORT:

  • If the patch is a cherry-pick from Linux mainline with no changes at all
    • tag the patch subject with UPSTREAM:.
    • add upstream commit information with a (cherry picked from commit ...) line
    • Example:
      • if the upstream commit message is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>
  • then Joe Smith would upload the patch for the common kernel as
        UPSTREAM: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch requires any changes from the upstream version, tag the patch with BACKPORT: instead of UPSTREAM:.
    • use the same tags as UPSTREAM:
    • add comments about the changes under the (cherry picked from commit ...) line
    • Example:
        BACKPORT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        [joe: Resolved minor conflict in drivers/foo/bar.c ]
        Signed-off-by: Joe Smith <joe.smith@foo.org>

Requirements for other backports: FROMGIT:, FROMLIST:,

  • If the patch has been merged into an upstream maintainer tree, but has not yet been merged into Linux mainline
    • tag the patch subject with FROMGIT:
    • add info on where the patch came from as (cherry picked from commit <sha1> <repo> <branch>). This must be a stable maintainer branch (not rebased, so don't use linux-next for example).
    • if changes were required, use BACKPORT: FROMGIT:
    • Example:
      • if the commit message in the maintainer tree is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>
  • then Joe Smith would upload the patch for the common kernel as
        FROMGIT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        (cherry picked from commit 878a2fd9de10b03d11d2f622250285c7e63deace
         https://git.kernel.org/pub/scm/linux/kernel/git/foo/bar.git test-branch)
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch has been submitted to LKML, but not accepted into any maintainer tree
    • tag the patch subject with FROMLIST:
    • add a Link: tag with a link to the submittal on lore.kernel.org
    • add a Bug: tag with the Android bug (required for patches not accepted into a maintainer tree)
    • if changes were required, use BACKPORT: FROMLIST:
    • Example:
        FROMLIST: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Link: https://lore.kernel.org/lkml/20190619171517.GA17557@someone.com/
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>

Requirements for Android-specific patches: ANDROID:

  • If the patch is fixing a bug to Android-specific code
    • tag the patch subject with ANDROID:
    • add a Fixes: tag that cites the patch with the bug
    • Example:
        ANDROID: fix android-specific bug in foobar.c

        This is the detailed description of the important fix

        Fixes: 1234abcd2468 ("foobar: add cool feature")
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch is a new feature
    • tag the patch subject with ANDROID:
    • add a Bug: tag with the Android bug (required for android-specific features)