linux-kernel - [PATCH v9 07/15] arm64: add support for polling in idle

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Message-Id: <20241107190818.522639-8-ankur.a.arora@oracle.com>
Date: Thu,  7 Nov 2024 11:08:10 -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-arch@...r.kernel.org
Cc: 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,
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        zhenglifeng1@...wei.com, joao.m.martins@...cle.com,
        boris.ostrovsky@...cle.com, konrad.wilk@...cle.com
Subject: [PATCH v9 07/15] arm64: add support for polling in idle

Polling in idle with poll_idle() needs TIF_POLLING_NRFLAG support,
and a cheap mechanism to do the actual polling via
smp_cond_load_relaxed_timeout().

Both of these are present on arm64. So, select ARCH_HAS_OPTIMIZED_POLL
to enable it.

Enabling this should help reduce the cost of remote wakeups, since if
the target sets TIF_POLLING_NRFLAG (as it does while polling in idle),
the scheduler does those just by setting the need-resched bit. This
contrasts with sending an IPI, and incurring the cost of handling the
interrupt on the receiver.

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 fd9df6dcc593..43762c68e357 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -38,6 +38,7 @@ config ARM64
 	select ARCH_HAS_MEM_ENCRYPT
 	select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
 	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
+	select ARCH_HAS_OPTIMIZED_POLL
 	select ARCH_HAS_PTE_DEVMAP
 	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_HW_PTE_YOUNG
-- 
2.43.5