linux-kernel - [PATCH] KVM: X86: Limit timer frequency with more smaller interval

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Date:   Sun, 29 Apr 2018 19:38:20 -0700
From:   Wanpeng Li <kernellwp@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Anthoine Bourgeois <anthoine.bourgeois@...de-group.com>
Subject: [PATCH] KVM: X86: Limit timer frequency with more smaller interval

From: Wanpeng Li <wanpengli@...cent.com>

Anthoine reported:
 The period used by Windows change over time but it can be 1 milliseconds
 or less. I saw the limit_periodic_timer_frequency print so 500
 microseconds is sometimes reached.

This patchs limits timer frequency with more smaller interval 200ms(5000Hz) 
to leave some headroom as Paolo suggested since Windows 10 changed the 
scheduler tick limit from 1024 Hz to 2048 Hz.

Reported-by: Anthoine Bourgeois <anthoine.bourgeois@...de-group.com>
Suggested-by: Paolo Bonzini <pbonzini@...hat.com> 
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Cc: Anthoine Bourgeois <anthoine.bourgeois@...de-group.com>
Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
 arch/x86/kvm/x86.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 51ecd38..dc47073 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -114,7 +114,7 @@ module_param(ignore_msrs, bool, S_IRUGO | S_IWUSR);
 static bool __read_mostly report_ignored_msrs = true;
 module_param(report_ignored_msrs, bool, S_IRUGO | S_IWUSR);
 
-unsigned int min_timer_period_us = 500;
+unsigned int min_timer_period_us = 200;
 module_param(min_timer_period_us, uint, S_IRUGO | S_IWUSR);
 
 static bool __read_mostly kvmclock_periodic_sync = true;
-- 
2.7.4