| Message ID | 20210429162233.116849-1-venkateshs@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | kvm: exit halt polling on need_resched() as well | expand |
On Thu, Apr 29, 2021 at 9:22 AM Venkatesh Srinivas <venkateshs@chromium.org> wrote: > > From: Benjamin Segall <bsegall@google.com> > > single_task_running() is usually more general than need_resched() > but CFS_BANDWIDTH throttling will use resched_task() when there > is just one task to get the task to block. This was causing > long-need_resched warnings and was likely allowing VMs to > overrun their quota when halt polling. > > Signed-off-by: Ben Segall <bsegall@google.com> > Signed-off-by: Venkatesh Srinivas <venkateshs@chromium.org> Reviewed-by: Jim Mattson <jmattson@google.com>
On Thu, Apr 29, 2021 at 9:22 AM Venkatesh Srinivas <venkateshs@chromium.org> wrote: > > From: Benjamin Segall <bsegall@google.com> > > single_task_running() is usually more general than need_resched() > but CFS_BANDWIDTH throttling will use resched_task() when there > is just one task to get the task to block. This was causing > long-need_resched warnings and was likely allowing VMs to > overrun their quota when halt polling. > > Signed-off-by: Ben Segall <bsegall@google.com> > Signed-off-by: Venkatesh Srinivas <venkateshs@chromium.org> Reviewed-by: David Matlack <dmatlack@google.com>
On 29.04.21 18:22, Venkatesh Srinivas wrote: > From: Benjamin Segall <bsegall@google.com> > > single_task_running() is usually more general than need_resched() > but CFS_BANDWIDTH throttling will use resched_task() when there > is just one task to get the task to block. This was causing > long-need_resched warnings and was likely allowing VMs to > overrun their quota when halt polling. > > Signed-off-by: Ben Segall <bsegall@google.com> > Signed-off-by: Venkatesh Srinivas <venkateshs@chromium.org> would that qualify for stable? > --- > virt/kvm/kvm_main.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 2799c6660cce..b9f12da6af0e 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -2973,7 +2973,8 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) > goto out; > } > poll_end = cur = ktime_get(); > - } while (single_task_running() && ktime_before(cur, stop)); > + } while (single_task_running() && !need_resched() && > + ktime_before(cur, stop)); > } > > prepare_to_rcuwait(&vcpu->wait); >
On 30/04/21 19:43, Christian Borntraeger wrote: > > > On 29.04.21 18:22, Venkatesh Srinivas wrote: >> From: Benjamin Segall <bsegall@google.com> >> >> single_task_running() is usually more general than need_resched() >> but CFS_BANDWIDTH throttling will use resched_task() when there >> is just one task to get the task to block. This was causing >> long-need_resched warnings and was likely allowing VMs to >> overrun their quota when halt polling. >> >> Signed-off-by: Ben Segall <bsegall@google.com> >> Signed-off-by: Venkatesh Srinivas <venkateshs@chromium.org> > > would that qualify for stable? Good idea indeed, I added the Cc. Paolo >> --- >> virt/kvm/kvm_main.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c >> index 2799c6660cce..b9f12da6af0e 100644 >> --- a/virt/kvm/kvm_main.c >> +++ b/virt/kvm/kvm_main.c >> @@ -2973,7 +2973,8 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) >> goto out; >> } >> poll_end = cur = ktime_get(); >> - } while (single_task_running() && ktime_before(cur, stop)); >> + } while (single_task_running() && !need_resched() && >> + ktime_before(cur, stop)); >> } >> >> prepare_to_rcuwait(&vcpu->wait); >> >
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 2799c6660cce..b9f12da6af0e 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2973,7 +2973,8 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) goto out; } poll_end = cur = ktime_get(); - } while (single_task_running() && ktime_before(cur, stop)); + } while (single_task_running() && !need_resched() && + ktime_before(cur, stop)); } prepare_to_rcuwait(&vcpu->wait);