On Fri, Oct 14, 2022 at 9:34 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> On Fri, Oct 14, 2022, Wang, Wei W wrote:
> > On Tuesday, October 11, 2022 6:06 AM, Vipin Sharma wrote:
> > > Pin vCPUs to a host physical CPUs (pCPUs) in dirty_log_perf_test and optionally
> > > pin the main application thread to a physical cpu if provided. All tests based on
> > > perf_test_util framework can take advantage of it if needed.
> > >
> > > While at it, I changed atoi() to atoi_paranoid(), atoi_positive,
> > > atoi_non_negative() in other tests, sorted command line options alphabetically
> > > in dirty_log_perf_test, and added break between -e and -g which was missed in
> > > original commit when -e was introduced.
> >
> > Just curious why not re-using the existing tools (e.g. taskset) to do the pinning?
>
> IIUC, you're suggesting the test give tasks meaningful names so that the user can
> do taskset on the appropriate tasks? The goal is to ensure vCPUs are pinned before
> they do any meaningful work. I don't see how that can be accomplished with taskset
> without some form of hook in the test to effectively pause the test until the user
> (or some run script) is ready to continue.
A taskset approach would also be more difficult to incorporate into
automated runs of dirty_log_perf_test.
>
> Pinning aside, naming the threads is a great idea! That would definitely help
> debug, e.g. if one vCPU gets stuck or is lagging behind.
+1
>
> >
> > For example, with below changes:
> > diff --git a/tools/testing/selftests/kvm/lib/perf_test_util.c b/tools/testing/se lftests/kvm/lib/perf_test_util.c
> > index 9618b37c66f7..aac58d1acb3c 100644
> > --- a/tools/testing/selftests/kvm/lib/perf_test_util.c
> > +++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
> > @@ -264,6 +264,7 @@ void perf_test_start_vcpu_threads(int nr_vcpus,
> > void (*vcpu_fn)(struct perf_test_vcpu_args *))
> > {
> > int i;
> > + char vcpu_name[5];
> >
> > vcpu_thread_fn = vcpu_fn;
> > WRITE_ONCE(all_vcpu_threads_running, false);
> > @@ -275,6 +276,8 @@ void perf_test_start_vcpu_threads(int nr_vcpus,
> > WRITE_ONCE(vcpu->running, false);
> >
> > pthread_create(&vcpu->thread, NULL, vcpu_thread_main, vcpu);
> > + sprintf(vcpu_name, "%s%d", "vcpu", i);
> > + pthread_setname_np(vcpu->thread, vcpu_name);
> > }
> >
> > and with top we can get
> > PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
> > 4464 root 20 0 4248684 4.0g 1628 R 99.9 26.2 0:50.97 dirty_log_perf_
> > 4467 root 20 0 4248684 4.0g 1628 R 99.9 26.2 0:50.93 vcpu0
> > 4469 root 20 0 4248684 4.0g 1628 R 99.9 26.2 0:50.93 vcpu2
> > 4470 root 20 0 4248684 4.0g 1628 R 99.9 26.2 0:50.94 vcpu3
> > 4468 root 20 0 4248684 4.0g 1628 R 99.7 26.2 0:50.93 vcpu1
