KVM: LAPIC: Reduce world switch latency caused by timer_advance_ns

Browse source

All the checks in lapic_timer_int_injected(), __kvm_wait_lapic_expire(), and
these function calls waste cpu cycles when the timer mode is not tscdeadline.
We can observe ~1.3% world switch time overhead by kvm-unit-tests/vmexit.flat
vmcall testing on AMD server. This patch reduces the world switch latency
caused by timer_advance_ns feature when the timer mode is not tscdeadline by
simpling move the check against apic->lapic_timer.expired_tscdeadline much
earlier.

Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Message-Id: <1599731444-3525-7-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

...

This commit is contained in:

Wanpeng Li 2020-09-10 17:50:41 +08:00 • committed by Paolo Bonzini

parent 68ca7663c7

commit 010fd37fdd

3 changed files with 7 additions and 12 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

11

arch/x86/kvm/lapic.c

View file

4

arch/x86/kvm/svm/svm.c

View file

4

arch/x86/kvm/vmx/vmx.c

View file