| Message ID | 1569572822-28942-1-git-send-email-wanpengli@tencent.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: Don't shrink/grow vCPU halt_poll_ns if host side polling is disabled | expand |
On Fri, Sep 27, 2019 at 04:27:02PM +0800, Wanpeng Li wrote: > From: Wanpeng Li <wanpengli@tencent.com> > > Don't waste cycles to shrink/grow vCPU halt_poll_ns if host > side polling is disabled. > > Cc: Marcelo Tosatti <mtosatti@redhat.com> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > --- > virt/kvm/kvm_main.c | 28 +++++++++++++++------------- > 1 file changed, 15 insertions(+), 13 deletions(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index e6de315..b368be4 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -2359,20 +2359,22 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) > kvm_arch_vcpu_unblocking(vcpu); > block_ns = ktime_to_ns(cur) - ktime_to_ns(start); > > - if (!vcpu_valid_wakeup(vcpu)) > - shrink_halt_poll_ns(vcpu); > - else if (halt_poll_ns) { > - if (block_ns <= vcpu->halt_poll_ns) > - ; > - /* we had a long block, shrink polling */ > - else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns) > + if (!kvm_arch_no_poll(vcpu)) { Can vcpu->halt_poll_ns be cached and used both here and in the similar check above? E.g.: unsigned int vcpu_halt_poll_ns; vcpu_halt_poll_ns = kvm_arch_no_poll(vcpu) ? 0 : vcpu->halt_poll_ns; if (vcpu_halt_poll_ns) { ... } > + if (!vcpu_valid_wakeup(vcpu)) > shrink_halt_poll_ns(vcpu); > - /* we had a short halt and our poll time is too small */ > - else if (vcpu->halt_poll_ns < halt_poll_ns && > - block_ns < halt_poll_ns) > - grow_halt_poll_ns(vcpu); > - } else > - vcpu->halt_poll_ns = 0; > + else if (halt_poll_ns) { > + if (block_ns <= vcpu->halt_poll_ns) > + ; > + /* we had a long block, shrink polling */ > + else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns) > + shrink_halt_poll_ns(vcpu); > + /* we had a short halt and our poll time is too small */ > + else if (vcpu->halt_poll_ns < halt_poll_ns && > + block_ns < halt_poll_ns) > + grow_halt_poll_ns(vcpu); > + } else > + vcpu->halt_poll_ns = 0; Not your code, but it'd be a good time to add braces to the 'if' and 'else'. Per Documentation/process/coding-style.rst: Do not unnecessarily use braces where a single statement will do. ... This does not apply if only one branch of a conditional statement is a single statement; in the latter case use braces in both branches: if (condition) { do_this(); do_that(); } else { otherwise(); } > + } > > trace_kvm_vcpu_wakeup(block_ns, waited, vcpu_valid_wakeup(vcpu)); > kvm_arch_vcpu_block_finish(vcpu); > -- > 2.7.4 >
On Fri, Sep 27, 2019 at 04:27:02PM +0800, Wanpeng Li wrote: > From: Wanpeng Li <wanpengli@tencent.com> > > Don't waste cycles to shrink/grow vCPU halt_poll_ns if host > side polling is disabled. > > Cc: Marcelo Tosatti <mtosatti@redhat.com> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > --- > virt/kvm/kvm_main.c | 28 +++++++++++++++------------- > 1 file changed, 15 insertions(+), 13 deletions(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index e6de315..b368be4 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -2359,20 +2359,22 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) > kvm_arch_vcpu_unblocking(vcpu); > block_ns = ktime_to_ns(cur) - ktime_to_ns(start); > > - if (!vcpu_valid_wakeup(vcpu)) > - shrink_halt_poll_ns(vcpu); > - else if (halt_poll_ns) { > - if (block_ns <= vcpu->halt_poll_ns) > - ; > - /* we had a long block, shrink polling */ > - else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns) > + if (!kvm_arch_no_poll(vcpu)) { > + if (!vcpu_valid_wakeup(vcpu)) > shrink_halt_poll_ns(vcpu); > - /* we had a short halt and our poll time is too small */ > - else if (vcpu->halt_poll_ns < halt_poll_ns && > - block_ns < halt_poll_ns) > - grow_halt_poll_ns(vcpu); > - } else > - vcpu->halt_poll_ns = 0; > + else if (halt_poll_ns) { > + if (block_ns <= vcpu->halt_poll_ns) > + ; > + /* we had a long block, shrink polling */ > + else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns) > + shrink_halt_poll_ns(vcpu); > + /* we had a short halt and our poll time is too small */ > + else if (vcpu->halt_poll_ns < halt_poll_ns && > + block_ns < halt_poll_ns) > + grow_halt_poll_ns(vcpu); > + } else > + vcpu->halt_poll_ns = 0; > + } > > trace_kvm_vcpu_wakeup(block_ns, waited, vcpu_valid_wakeup(vcpu)); > kvm_arch_vcpu_block_finish(vcpu); > -- > 2.7.4 Looks good.
On Fri, 27 Sep 2019 at 22:42, Sean Christopherson <sean.j.christopherson@intel.com> wrote: > > On Fri, Sep 27, 2019 at 04:27:02PM +0800, Wanpeng Li wrote: > > From: Wanpeng Li <wanpengli@tencent.com> > > > > Don't waste cycles to shrink/grow vCPU halt_poll_ns if host > > side polling is disabled. > > > > Cc: Marcelo Tosatti <mtosatti@redhat.com> > > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > > --- > > virt/kvm/kvm_main.c | 28 +++++++++++++++------------- > > 1 file changed, 15 insertions(+), 13 deletions(-) > > > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > index e6de315..b368be4 100644 > > --- a/virt/kvm/kvm_main.c > > +++ b/virt/kvm/kvm_main.c > > @@ -2359,20 +2359,22 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) > > kvm_arch_vcpu_unblocking(vcpu); > > block_ns = ktime_to_ns(cur) - ktime_to_ns(start); > > > > - if (!vcpu_valid_wakeup(vcpu)) > > - shrink_halt_poll_ns(vcpu); > > - else if (halt_poll_ns) { > > - if (block_ns <= vcpu->halt_poll_ns) > > - ; > > - /* we had a long block, shrink polling */ > > - else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns) > > + if (!kvm_arch_no_poll(vcpu)) { > > Can vcpu->halt_poll_ns be cached and used both here and in the similar > check above? E.g.: > > unsigned int vcpu_halt_poll_ns; > > vcpu_halt_poll_ns = kvm_arch_no_poll(vcpu) ? 0 : vcpu->halt_poll_ns; > > if (vcpu_halt_poll_ns) { > ... > } This is not correct, !kvm_arch_no_poll(vcpu) && vcpu->halt_poll_ns == 0, you will stop grow. > > > + if (!vcpu_valid_wakeup(vcpu)) > > shrink_halt_poll_ns(vcpu); > > - /* we had a short halt and our poll time is too small */ > > - else if (vcpu->halt_poll_ns < halt_poll_ns && > > - block_ns < halt_poll_ns) > > - grow_halt_poll_ns(vcpu); > > - } else > > - vcpu->halt_poll_ns = 0; > > + else if (halt_poll_ns) { > > + if (block_ns <= vcpu->halt_poll_ns) > > + ; > > + /* we had a long block, shrink polling */ > > + else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns) > > + shrink_halt_poll_ns(vcpu); > > + /* we had a short halt and our poll time is too small */ > > + else if (vcpu->halt_poll_ns < halt_poll_ns && > > + block_ns < halt_poll_ns) > > + grow_halt_poll_ns(vcpu); > > + } else > > + vcpu->halt_poll_ns = 0; > > > Not your code, Not the truth. :) >but it'd be a good time to add braces to the 'if' and > 'else'. Per Documentation/process/coding-style.rst: > > Do not unnecessarily use braces where a single statement will do. > > ... > > This does not apply if only one branch of a conditional statement is a single > statement; in the latter case use braces in both branches: > > if (condition) { > do_this(); > do_that(); > } else { > otherwise(); > } Will do in v2. Wanpeng
On Sat, 28 Sep 2019 at 01:24, Marcelo Tosatti <mtosatti@redhat.com> wrote: > > On Fri, Sep 27, 2019 at 04:27:02PM +0800, Wanpeng Li wrote: > > From: Wanpeng Li <wanpengli@tencent.com> > > > > Don't waste cycles to shrink/grow vCPU halt_poll_ns if host > > side polling is disabled. > > > > Cc: Marcelo Tosatti <mtosatti@redhat.com> > > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > > --- > > virt/kvm/kvm_main.c | 28 +++++++++++++++------------- > > 1 file changed, 15 insertions(+), 13 deletions(-) > > > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > index e6de315..b368be4 100644 > > --- a/virt/kvm/kvm_main.c > > +++ b/virt/kvm/kvm_main.c > > @@ -2359,20 +2359,22 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) > > kvm_arch_vcpu_unblocking(vcpu); > > block_ns = ktime_to_ns(cur) - ktime_to_ns(start); > > > > - if (!vcpu_valid_wakeup(vcpu)) > > - shrink_halt_poll_ns(vcpu); > > - else if (halt_poll_ns) { > > - if (block_ns <= vcpu->halt_poll_ns) > > - ; > > - /* we had a long block, shrink polling */ > > - else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns) > > + if (!kvm_arch_no_poll(vcpu)) { > > + if (!vcpu_valid_wakeup(vcpu)) > > shrink_halt_poll_ns(vcpu); > > - /* we had a short halt and our poll time is too small */ > > - else if (vcpu->halt_poll_ns < halt_poll_ns && > > - block_ns < halt_poll_ns) > > - grow_halt_poll_ns(vcpu); > > - } else > > - vcpu->halt_poll_ns = 0; > > + else if (halt_poll_ns) { > > + if (block_ns <= vcpu->halt_poll_ns) > > + ; > > + /* we had a long block, shrink polling */ > > + else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns) > > + shrink_halt_poll_ns(vcpu); > > + /* we had a short halt and our poll time is too small */ > > + else if (vcpu->halt_poll_ns < halt_poll_ns && > > + block_ns < halt_poll_ns) > > + grow_halt_poll_ns(vcpu); > > + } else > > + vcpu->halt_poll_ns = 0; > > + } > > > > trace_kvm_vcpu_wakeup(block_ns, waited, vcpu_valid_wakeup(vcpu)); > > kvm_arch_vcpu_block_finish(vcpu); > > -- > > 2.7.4 > > Looks good. I will add your ACK in v2. Wanpeng
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index e6de315..b368be4 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2359,20 +2359,22 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) kvm_arch_vcpu_unblocking(vcpu); block_ns = ktime_to_ns(cur) - ktime_to_ns(start); - if (!vcpu_valid_wakeup(vcpu)) - shrink_halt_poll_ns(vcpu); - else if (halt_poll_ns) { - if (block_ns <= vcpu->halt_poll_ns) - ; - /* we had a long block, shrink polling */ - else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns) + if (!kvm_arch_no_poll(vcpu)) { + if (!vcpu_valid_wakeup(vcpu)) shrink_halt_poll_ns(vcpu); - /* we had a short halt and our poll time is too small */ - else if (vcpu->halt_poll_ns < halt_poll_ns && - block_ns < halt_poll_ns) - grow_halt_poll_ns(vcpu); - } else - vcpu->halt_poll_ns = 0; + else if (halt_poll_ns) { + if (block_ns <= vcpu->halt_poll_ns) + ; + /* we had a long block, shrink polling */ + else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns) + shrink_halt_poll_ns(vcpu); + /* we had a short halt and our poll time is too small */ + else if (vcpu->halt_poll_ns < halt_poll_ns && + block_ns < halt_poll_ns) + grow_halt_poll_ns(vcpu); + } else + vcpu->halt_poll_ns = 0; + } trace_kvm_vcpu_wakeup(block_ns, waited, vcpu_valid_wakeup(vcpu)); kvm_arch_vcpu_block_finish(vcpu);