From: Paolo Bonzini <pbonzini@redhat.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: [PATCH] kvm: x86: disable shattered huge page recovery for PREEMPT_RT.
Date: Wed, 13 Nov 2019 15:47:19 +0100 [thread overview]
Message-ID: <1573656439-16252-1-git-send-email-pbonzini@redhat.com> (raw)
If a huge page is recovered (and becomes no executable) while another
thread is executing it, the resulting contention on mmu_lock can cause
latency spikes. Disabling recovery for PREEMPT_RT kernels fixes this
issue.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/mmu.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index fd6012eef9c9..cf718fa23dff 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -51,7 +51,12 @@
extern bool itlb_multihit_kvm_mitigation;
static int __read_mostly nx_huge_pages = -1;
+#ifdef CONFIG_PREEMPT_RT
+/* Recovery can cause latency spikes, disable it for PREEMPT_RT. */
+static uint __read_mostly nx_huge_pages_recovery_ratio = 0;
+#else
static uint __read_mostly nx_huge_pages_recovery_ratio = 60;
+#endif
static int set_nx_huge_pages(const char *val, const struct kernel_param *kp);
static int set_nx_huge_pages_recovery_ratio(const char *val, const struct kernel_param *kp);
--
1.8.3.1
reply other threads:[~2019-11-13 14:47 UTC|newest]
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