linux-kernel - [PATCH v10 05/11] arm64: add support for poll

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Message-Id: <20250218213337.377987-6-ankur.a.arora@oracle.com>
Date: Tue, 18 Feb 2025 13:33:31 -0800
From: Ankur Arora <ankur.a.arora@...cle.com>
To: linux-pm@...r.kernel.org, kvm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org
Cc: catalin.marinas@....com, will@...nel.org, x86@...nel.org,
        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: [PATCH v10 05/11] arm64: add support for poll_idle()

Polling in idle helps reduce the cost of remote wakeups: if the target
sets TIF_POLLING_NRFLAG (as it does while polling in idle), the scheduler
can do remote wakeups just by setting the TIF_NEED_RESCHED.

This contrasts with sending an IPI, and incurring the cost of handling
the cost of the interrupt on the receiver.

Enabling poll_idle() needs a cheap mechanism to do the actual polling
(via smp_cond_load_relaxed_timewait()) and TIF_POLLING_NRFLAG support.

arm64 has both of these. So, select ARCH_HAS_OPTIMIZED_POLL.

Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
---
 arch/arm64/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 100570a048c5..d96a6c6d8894 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -39,6 +39,7 @@ config ARM64
 	select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
 	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
 	select ARCH_HAS_NONLEAF_PMD_YOUNG if ARM64_HAFT
+	select ARCH_HAS_OPTIMIZED_POLL
 	select ARCH_HAS_PTE_DEVMAP
 	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_HW_PTE_YOUNG
-- 
2.43.5