linux-kernel - [PATCH v2 1/2] irqchip/gic-v4.1: Reduce the delay time of the poll on the GICR

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Date:   Sat, 28 Nov 2020 22:18:56 +0800
From:   Shenming Lu <lushenming@...wei.com>
To:     Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Jason Cooper" <jason@...edaemon.net>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.cs.columbia.edu>, <kvm@...r.kernel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        Christoffer Dall <christoffer.dall@....com>
CC:     <wanghaibin.wang@...wei.com>, <yuzenghui@...wei.com>,
        <lushenming@...wei.com>
Subject: [PATCH v2 1/2] irqchip/gic-v4.1: Reduce the delay time of the poll on the GICR_VPENDBASER.Dirty bit

The 10 delay_us of the poll on the GICR_VPENDBASER.Dirty bit is too
high, which might greatly affect the total scheduling latency of a
vCPU in our measurement. So we reduce it to 1 to lessen the impact.

Signed-off-by: Shenming Lu <lushenming@...wei.com>
---
 drivers/irqchip/irq-gic-v3-its.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 0fec31931e11..22f427135c6b 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -3809,7 +3809,7 @@ static void its_wait_vpt_parse_complete(void)
 	WARN_ON_ONCE(readq_relaxed_poll_timeout_atomic(vlpi_base + GICR_VPENDBASER,
 						       val,
 						       !(val & GICR_VPENDBASER_Dirty),
-						       10, 500));
+						       1, 500));
 }
 
 static void its_vpe_schedule(struct its_vpe *vpe)
-- 
2.23.0