On Thu, 10 Oct 2019 12:28:50 +0200
Christian Borntraeger <borntraeger@xxxxxxxxxx> wrote:
> On 10.10.19 12:25, David Hildenbrand wrote:
> > On 10.10.19 12:21, Christian Borntraeger wrote:
> >> To analyze some performance issues with lock contention and scheduling
> >> it is nice to know when diag9c did not result in any action.
> >> At the same time avoid calling the scheduler (which can be expensive)
> >> if we know that it does not make sense.
> >>
> >> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> >> ---
> >> arch/s390/include/asm/kvm_host.h | 2 ++
> >> arch/s390/kvm/diag.c | 23 +++++++++++++++++++----
> >> arch/s390/kvm/kvm-s390.c | 2 ++
> >> 3 files changed, 23 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> >> index abe60268335d..743cd5a63b37 100644
> >> --- a/arch/s390/include/asm/kvm_host.h
> >> +++ b/arch/s390/include/asm/kvm_host.h
> >> @@ -392,6 +392,8 @@ struct kvm_vcpu_stat {
> >> u64 diagnose_10;
> >> u64 diagnose_44;
> >> u64 diagnose_9c;
> >> + u64 diagnose_9c_success;
> >> + u64 diagnose_9c_ignored;
> >
> > Can't you derive the one from the other with diagnose_9c? Just sayin,
> > one would be sufficient.
>
> You mean diagnose9c = diagnose_9c_success + diagnose_9c_ignored anyway so this is redundant?
> Could just do diagnose_9c and diagnose_9c_ignored if you prefer that.
Voting for that :)
>
>
> >
> >> u64 diagnose_258;
> >> u64 diagnose_308;
> >> u64 diagnose_500;
> >> diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
> >> index 45634b3d2e0a..2c729f020585 100644
> >> --- a/arch/s390/kvm/diag.c
> >> +++ b/arch/s390/kvm/diag.c
> >> @@ -158,14 +158,29 @@ static int __diag_time_slice_end_directed(struct kvm_vcpu *vcpu)
> >>
> >> tid = vcpu->run->s.regs.gprs[(vcpu->arch.sie_block->ipa & 0xf0) >> 4];
> >> vcpu->stat.diagnose_9c++;
> >> - VCPU_EVENT(vcpu, 5, "diag time slice end directed to %d", tid);
> >>
> >> + /* yield to self */
> >> if (tid == vcpu->vcpu_id)
> >> - return 0;
> >> + goto no_yield;
> >>
> >> + /* yield to invalid */
> >> tcpu = kvm_get_vcpu_by_id(vcpu->kvm, tid);
> >> - if (tcpu)
> >> - kvm_vcpu_yield_to(tcpu);
> >> + if (!tcpu)
> >> + goto no_yield;
> >> +
> >> + /* target already running */
> >> + if (tcpu->cpu >= 0)
> >> + goto no_yield;
> >
> > Wonder if it's wort moving this optimization to a separate patch.
>
> Could do if you prefer that.
Voting for that as well :)
>
>
> >
> >> +
> >> + if (kvm_vcpu_yield_to(tcpu) <= 0)
> >> + goto no_yield;
> >> +
> >> + VCPU_EVENT(vcpu, 5, "diag time slice end directed to %d: done", tid);
> >> + vcpu->stat.diagnose_9c_success++;
> >> + return 0;
> >> +no_yield:
> >> + VCPU_EVENT(vcpu, 5, "diag time slice end directed to %d: ignored", tid);
> >> + vcpu->stat.diagnose_9c_ignored++;
> >> return 0;
> >> }
> >>
> >> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> >> index 4a3bc40ca1a4..b368e835f2f7 100644
> >> --- a/arch/s390/kvm/kvm-s390.c
> >> +++ b/arch/s390/kvm/kvm-s390.c
> >> @@ -155,6 +155,8 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
> >> { "instruction_diag_10", VCPU_STAT(diagnose_10) },
> >> { "instruction_diag_44", VCPU_STAT(diagnose_44) },
> >> { "instruction_diag_9c", VCPU_STAT(diagnose_9c) },
> >> + { "diag_9c_success", VCPU_STAT(diagnose_9c_success) },
> >> + { "diag_9c_ignored", VCPU_STAT(diagnose_9c_ignored) },
> >> { "instruction_diag_258", VCPU_STAT(diagnose_258) },
> >> { "instruction_diag_308", VCPU_STAT(diagnose_308) },
> >> { "instruction_diag_500", VCPU_STAT(diagnose_500) },
> >>
> >
> >
>
