| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <87h66bdwo3.fsf@oracle.com>
Date: Mon, 06 Jan 2025 21:23:40 -0800
From: Ankur Arora <ankur.a.arora@...cle.com>
To: Ankur Arora <ankur.a.arora@...cle.com>
Cc: linux-pm@...r.kernel.org, kvm@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-arch@...r.kernel.org, catalin.marinas@....com, will@...nel.org,
tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
pbonzini@...hat.com, vkuznets@...hat.com, rafael@...nel.org,
daniel.lezcano@...aro.org, peterz@...radead.org, arnd@...db.de,
lenb@...nel.org, mark.rutland@....com, harisokn@...zon.com,
mtosatti@...hat.com, sudeep.holla@....com, cl@...two.org,
maz@...nel.org, misono.tomohiro@...itsu.com, maobibo@...ngson.cn,
zhenglifeng1@...wei.com, joao.m.martins@...cle.com,
boris.ostrovsky@...cle.com, konrad.wilk@...cle.com
Subject: Re: [PATCH v9 00/15] arm64: support poll_idle()
Just a ping on this to see if there are any further comments.
Thanks
Ankur
Ankur Arora <ankur.a.arora@...cle.com> writes:
> This patchset adds support for polling in idle via poll_idle() on
> arm64.
>
> There are two main changes in this version:
>
> 1. rework the series to take Catalin Marinas' comments on the semantics
> of smp_cond_load_relaxed() (and how earlier versions of this
> series were abusing them) into account.
>
> This also allows dropping of the somewhat strained connections
> between haltpoll and the event-stream.
>
> 2. earlier versions of this series were adding support for poll_idle()
> but only using it in the haltpoll driver. Add Lifeng's patch to
> broaden it out by also polling in acpi-idle.
>
> The benefit of polling in idle is to reduce the cost of remote wakeups.
> When enabled, these can be done just by setting the need-resched bit,
> instead of sending an IPI, and incurring the cost of handling the
> interrupt on the receiver side. When running on a VM it also saves
> the cost of WFE trapping (when enabled.)
>
> Comparing sched-pipe performance on a guest VM:
>
> # perf stat -r 5 --cpu 4,5 -e task-clock,cycles,instructions,sched:sched_wake_idle_without_ipi \
> perf bench sched pipe -l 1000000 -c 4
>
> # no polling in idle
>
> Performance counter stats for 'CPU(s) 4,5' (5 runs):
>
> 25,229.57 msec task-clock # 2.000 CPUs utilized ( +- 7.75% )
> 45,821,250,284 cycles # 1.816 GHz ( +- 10.07% )
> 26,557,496,665 instructions # 0.58 insn per cycle ( +- 0.21% )
> 0 sched:sched_wake_idle_without_ipi # 0.000 /sec
>
> 12.615 +- 0.977 seconds time elapsed ( +- 7.75% )
>
>
> # polling in idle (with haltpoll):
>
> Performance counter stats for 'CPU(s) 4,5' (5 runs):
>
> 15,131.58 msec task-clock # 2.000 CPUs utilized ( +- 10.00% )
> 34,158,188,839 cycles # 2.257 GHz ( +- 6.91% )
> 20,824,950,916 instructions # 0.61 insn per cycle ( +- 0.09% )
> 1,983,822 sched:sched_wake_idle_without_ipi # 131.105 K/sec ( +- 0.78% )
>
> 7.566 +- 0.756 seconds time elapsed ( +- 10.00% )
>
> Tomohiro Misono and Haris Okanovic also report similar latency
> improvements on Grace and Graviton systems (for v7) [1] [2].
> Lifeng also reports improved context switch latency on a bare-metal
> machine with acpi-idle [3].
>
> The series is in four parts:
>
> - patches 1-4,
>
> "asm-generic: add barrier smp_cond_load_relaxed_timeout()"
> "cpuidle/poll_state: poll via smp_cond_load_relaxed_timeout()"
> "cpuidle: rename ARCH_HAS_CPU_RELAX to ARCH_HAS_OPTIMIZED_POLL"
> "Kconfig: move ARCH_HAS_OPTIMIZED_POLL to arch/Kconfig"
>
> add smp_cond_load_relaxed_timeout() and switch poll_idle() to
> using it. Also, do some munging of related kconfig options.
>
> - patches 5-7,
>
> "arm64: barrier: add support for smp_cond_relaxed_timeout()"
> "arm64: define TIF_POLLING_NRFLAG"
> "arm64: add support for polling in idle"
>
> add support for the new barrier, the polling flag and enable
> poll_idle() support.
>
> - patches 8, 9-13,
>
> "ACPI: processor_idle: Support polling state for LPI"
>
> "cpuidle-haltpoll: define arch_haltpoll_want()"
> "governors/haltpoll: drop kvm_para_available() check"
> "cpuidle-haltpoll: condition on ARCH_CPUIDLE_HALTPOLL"
> "arm64: idle: export arch_cpu_idle"
> "arm64: support cpuidle-haltpoll"
>
> add support for polling via acpi-idle, and cpuidle-haltpoll.
>
> - patches 14, 15,
> "arm64/delay: move some constants out to a separate header"
> "arm64: support WFET in smp_cond_relaxed_timeout()"
>
> are RFC patches to enable WFET support.
>
> Changelog:
>
> v9:
>
> - reworked the series to address a comment from Catalin Marinas
> about how v8 was abusing semantics of smp_cond_load_relaxed().
> - add poll_idle() support in acpi-idle (Lifeng Zheng)
> - dropped some earlier "Tested-by", "Reviewed-by" due to the
> above rework.
>
> v8: No logic changes. Largely respin of v7, with changes
> noted below:
>
> - move selection of ARCH_HAS_OPTIMIZED_POLL on arm64 to its
> own patch.
> (patch-9 "arm64: select ARCH_HAS_OPTIMIZED_POLL")
>
> - address comments simplifying arm64 support (Will Deacon)
> (patch-11 "arm64: support cpuidle-haltpoll")
>
> v7: No significant logic changes. Mostly a respin of v6.
>
> - minor cleanup in poll_idle() (Christoph Lameter)
> - fixes conflicts due to code movement in arch/arm64/kernel/cpuidle.c
> (Tomohiro Misono)
>
> v6:
>
> - reordered the patches to keep poll_idle() and ARCH_HAS_OPTIMIZED_POLL
> changes together (comment from Christoph Lameter)
> - threshes out the commit messages a bit more (comments from Christoph
> Lameter, Sudeep Holla)
> - also rework selection of cpuidle-haltpoll. Now selected based
> on the architectural selection of ARCH_CPUIDLE_HALTPOLL.
> - moved back to arch_haltpoll_want() (comment from Joao Martins)
> Also, arch_haltpoll_want() now takes the force parameter and is
> now responsible for the complete selection (or not) of haltpoll.
> - fixes the build breakage on i386
> - fixes the cpuidle-haltpoll module breakage on arm64 (comment from
> Tomohiro Misono, Haris Okanovic)
>
> v5:
> - rework the poll_idle() loop around smp_cond_load_relaxed() (review
> comment from Tomohiro Misono.)
> - also rework selection of cpuidle-haltpoll. Now selected based
> on the architectural selection of ARCH_CPUIDLE_HALTPOLL.
> - arch_haltpoll_supported() (renamed from arch_haltpoll_want()) on
> arm64 now depends on the event-stream being enabled.
> - limit POLL_IDLE_RELAX_COUNT on arm64 (review comment from Haris Okanovic)
> - ARCH_HAS_CPU_RELAX is now renamed to ARCH_HAS_OPTIMIZED_POLL.
>
> v4 changes from v3:
> - change 7/8 per Rafael input: drop the parens and use ret for the final check
> - add 8/8 which renames the guard for building poll_state
>
> v3 changes from v2:
> - fix 1/7 per Petr Mladek - remove ARCH_HAS_CPU_RELAX from arch/x86/Kconfig
> - add Ack-by from Rafael Wysocki on 2/7
>
> v2 changes from v1:
> - added patch 7 where we change cpu_relax with smp_cond_load_relaxed per PeterZ
> (this improves by 50% at least the CPU cycles consumed in the tests above:
> 10,716,881,137 now vs 14,503,014,257 before)
> - removed the ifdef from patch 1 per RafaelW
>
> Please review.
>
> [1] https://lore.kernel.org/lkml/TY3PR01MB111481E9B0AF263ACC8EA5D4AE5BA2@TY3PR01MB11148.jpnprd01.prod.outlook.com/
> [2] https://lore.kernel.org/lkml/104d0ec31cb45477e27273e089402d4205ee4042.camel@amazon.com/
> [3] https://lore.kernel.org/lkml/f8a1f85b-c4bf-4c38-81bf-728f72a4f2fe@huawei.com/
>
> Ankur Arora (10):
> asm-generic: add barrier smp_cond_load_relaxed_timeout()
> cpuidle/poll_state: poll via smp_cond_load_relaxed_timeout()
> cpuidle: rename ARCH_HAS_CPU_RELAX to ARCH_HAS_OPTIMIZED_POLL
> arm64: barrier: add support for smp_cond_relaxed_timeout()
> arm64: add support for polling in idle
> cpuidle-haltpoll: condition on ARCH_CPUIDLE_HALTPOLL
> arm64: idle: export arch_cpu_idle
> arm64: support cpuidle-haltpoll
> arm64/delay: move some constants out to a separate header
> arm64: support WFET in smp_cond_relaxed_timeout()
>
> Joao Martins (4):
> Kconfig: move ARCH_HAS_OPTIMIZED_POLL to arch/Kconfig
> arm64: define TIF_POLLING_NRFLAG
> cpuidle-haltpoll: define arch_haltpoll_want()
> governors/haltpoll: drop kvm_para_available() check
>
> Lifeng Zheng (1):
> ACPI: processor_idle: Support polling state for LPI
>
> arch/Kconfig | 3 ++
> arch/arm64/Kconfig | 7 +++
> arch/arm64/include/asm/barrier.h | 62 ++++++++++++++++++++++-
> arch/arm64/include/asm/cmpxchg.h | 26 ++++++----
> arch/arm64/include/asm/cpuidle_haltpoll.h | 20 ++++++++
> arch/arm64/include/asm/delay-const.h | 25 +++++++++
> arch/arm64/include/asm/thread_info.h | 2 +
> arch/arm64/kernel/idle.c | 1 +
> arch/arm64/lib/delay.c | 13 ++---
> arch/x86/Kconfig | 5 +-
> arch/x86/include/asm/cpuidle_haltpoll.h | 1 +
> arch/x86/kernel/kvm.c | 13 +++++
> drivers/acpi/processor_idle.c | 43 +++++++++++++---
> drivers/cpuidle/Kconfig | 5 +-
> drivers/cpuidle/Makefile | 2 +-
> drivers/cpuidle/cpuidle-haltpoll.c | 12 +----
> drivers/cpuidle/governors/haltpoll.c | 6 +--
> drivers/cpuidle/poll_state.c | 27 +++-------
> drivers/idle/Kconfig | 1 +
> include/asm-generic/barrier.h | 42 +++++++++++++++
> include/linux/cpuidle.h | 2 +-
> include/linux/cpuidle_haltpoll.h | 5 ++
> 22 files changed, 252 insertions(+), 71 deletions(-)
> create mode 100644 arch/arm64/include/asm/cpuidle_haltpoll.h
> create mode 100644 arch/arm64/include/asm/delay-const.h
--
ankur
Powered by blists - more mailing lists