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 <redacted>
---
 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