From: Wanpeng Li <kernellwp@gmail.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>
Subject: [PATCH v3 0/5] KVM: LAPIC: Optimize timer latency further
Date: Thu, 16 May 2019 11:06:15 +0800 [thread overview]
Message-ID: <1557975980-9875-1-git-send-email-wanpengli@tencent.com> (raw)
Advance lapic timer tries to hidden the hypervisor overhead between the
host emulated timer fires and the guest awares the timer is fired. However,
it just hidden the time between apic_timer_fn/handle_preemption_timer ->
wait_lapic_expire, instead of the real position of vmentry which is
mentioned in the orignial commit d0659d946be0 ("KVM: x86: add option to
advance tscdeadline hrtimer expiration"). There is 700+ cpu cycles between
the end of wait_lapic_expire and before world switch on my haswell desktop.
This patchset tries to narrow the last gap(wait_lapic_expire -> world switch),
it takes the real overhead time between apic_timer_fn/handle_preemption_timer
and before world switch into consideration when adaptively tuning timer
advancement. The patchset can reduce 40% latency (~1600+ cycles to ~1000+
cycles on a haswell desktop) for kvm-unit-tests/tscdeadline_latency when
testing busy waits.
v2 -> v3:
* expose 'kvm_timer.timer_advance_ns' to userspace
* move the tracepoint below guest_exit_irqoff()
* move wait_lapic_expire() before flushing the L1
v1 -> v2:
* fix indent in patch 1/4
* remove the wait_lapic_expire() tracepoint and expose by debugfs
* move the call to wait_lapic_expire() into vmx.c and svm.c
Wanpeng Li (5):
KVM: LAPIC: Extract adaptive tune timer advancement logic
KVM: LAPIC: Fix lapic_timer_advance_ns parameter overflow
KVM: LAPIC: Expose per-vCPU timer_advance_ns to userspace
KVM: LAPIC: Delay trace advance expire delta
KVM: LAPIC: Optimize timer latency further
arch/x86/kvm/debugfs.c | 16 +++++++++++++
arch/x86/kvm/lapic.c | 62 +++++++++++++++++++++++++++++---------------------
arch/x86/kvm/lapic.h | 3 ++-
arch/x86/kvm/svm.c | 4 ++++
arch/x86/kvm/vmx/vmx.c | 4 ++++
arch/x86/kvm/x86.c | 7 +++---
6 files changed, 65 insertions(+), 31 deletions(-)
--
2.7.4
next reply other threads:[~2019-05-16 3:06 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-16 3:06 Wanpeng Li [this message]
2019-05-16 3:06 ` [PATCH v3 1/5] KVM: LAPIC: Extract adaptive tune timer advancement logic Wanpeng Li
2019-05-16 3:06 ` [PATCH v3 2/5] KVM: LAPIC: Fix lapic_timer_advance_ns parameter overflow Wanpeng Li
2019-05-16 3:06 ` [PATCH v3 3/5] KVM: LAPIC: Expose per-vCPU timer_advance_ns to userspace Wanpeng Li
2019-05-17 20:05 ` Sean Christopherson
2019-05-20 8:43 ` Wanpeng Li
2019-05-16 3:06 ` [PATCH v3 4/5] KVM: LAPIC: Delay trace advance expire delta Wanpeng Li
2019-05-17 19:44 ` Sean Christopherson
2019-05-20 6:38 ` Wanpeng Li
2019-05-20 14:56 ` Sean Christopherson
2019-05-16 3:06 ` [PATCH v3 5/5] KVM: LAPIC: Optimize timer latency further Wanpeng Li
2019-05-17 19:50 ` Sean Christopherson
2019-05-20 8:19 ` Wanpeng Li
2019-05-20 15:08 ` Sean Christopherson
2019-06-12 9:35 [PATCH v3 0/5] " Wanpeng Li
2019-06-12 9:40 ` Wanpeng Li
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=1557975980-9875-1-git-send-email-wanpengli@tencent.com \
--to=kernellwp@gmail.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=rkrcmar@redhat.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.