From: Marc Zyngier <maz@kernel.org>
To: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Cc: James Morse <james.morse@arm.com>,
Julien Thierry <julien.thierry.kdev@gmail.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>
Subject: [PATCH 0/2] KVM: arm64: Reduce occurence of GICv4 doorbells on non-oversubscribed systems
Date: Thu, 7 Nov 2019 16:04:10 +0000 [thread overview]
Message-ID: <20191107160412.30301-1-maz@kernel.org> (raw)
As I was cleaning up some of the GICv4 code to make way for GICv4.1 it
occured to me that we could drastically reduce the impact of the GICv4
doorbells on systems that are not oversubscribed (each vcpu "owns" a
physical CPU).
The technique borrows its logic from the way we disable WFE trapping
when a vcpu is the only process on the CPU run-queue. If this vcpu is
the target of VLPIs, it is then beneficial not to trap blocking WFIs
and to leave the vcpu waiting for interrupts in guest state.
All we need to do here is to track whether VLPIs are associated to a
vcpu (which is easily done by using a counter that we update on MAPI,
DISCARD and MOVI).
It has been *very lightly* tested on a D05, and behaved pretty well in
my limited test cases (I get almost no doorbell at all in the non
oversubscribed case, and the usual hailstorm as soon as there is
oversubscription). I'd welcome some testing on more current HW.
Marc Zyngier (2):
KVM: vgic-v4: Track the number of VLPIs per vcpu
KVM: arm64: Opportunistically turn off WFI trapping when using direct
LPI injection
arch/arm/include/asm/kvm_emulate.h | 4 ++--
arch/arm64/include/asm/kvm_emulate.h | 9 +++++++--
include/linux/irqchip/arm-gic-v4.h | 2 ++
virt/kvm/arm/arm.c | 4 ++--
virt/kvm/arm/vgic/vgic-init.c | 1 +
virt/kvm/arm/vgic/vgic-its.c | 3 +++
virt/kvm/arm/vgic/vgic-v4.c | 2 ++
7 files changed, 19 insertions(+), 6 deletions(-)
--
2.20.1
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next reply other threads:[~2019-11-07 16:04 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-07 16:04 Marc Zyngier [this message]
2019-11-07 16:04 ` [PATCH 1/2] KVM: vgic-v4: Track the number of VLPIs per vcpu Marc Zyngier
2019-11-08 9:20 ` Zenghui Yu
2019-11-07 16:04 ` [PATCH 2/2] KVM: arm64: Opportunistically turn off WFI trapping when using direct LPI injection Marc Zyngier
2019-11-08 9:20 ` Zenghui Yu
2019-11-07 16:56 ` [PATCH 0/2] KVM: arm64: Reduce occurence of GICv4 doorbells on non-oversubscribed systems Christoffer Dall
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191107160412.30301-1-maz@kernel.org \
--to=maz@kernel.org \
--cc=james.morse@arm.com \
--cc=julien.thierry.kdev@gmail.com \
--cc=kvm@vger.kernel.org \
--cc=kvmarm@lists.cs.columbia.edu \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=suzuki.poulose@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).