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Message-ID: <CAHVum0d1Oaae0H4YO3GOJ5pCwV1vqNsE6n6mWV9wMGic6wN7_A@mail.gmail.com>
Date: Wed, 26 Oct 2022 11:17:42 -0700
From: Vipin Sharma <vipinsh@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: "Wang, Wei W" <wei.w.wang@...el.com>,
"pbonzini@...hat.com" <pbonzini@...hat.com>,
"dmatlack@...gle.com" <dmatlack@...gle.com>,
"andrew.jones@...ux.dev" <andrew.jones@...ux.dev>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 5/5] KVM: selftests: Allowing running
dirty_log_perf_test on specific CPUs
On Wed, Oct 26, 2022 at 8:44 AM Sean Christopherson <seanjc@...gle.com> wrote:
>
> On Wed, Oct 26, 2022, Wang, Wei W wrote:
> > On Saturday, October 22, 2022 5:18 AM, Vipin Sharma wrote:
> > > +static void pin_this_task_to_pcpu(uint32_t pcpu) {
> > > + cpu_set_t mask;
> > > + int r;
> > > +
> > > + CPU_ZERO(&mask);
> > > + CPU_SET(pcpu, &mask);
> > > + r = sched_setaffinity(0, sizeof(mask), &mask);
> > > + TEST_ASSERT(!r, "sched_setaffinity() failed for pCPU '%u'.\n", pcpu);
> > > +}
> > > +
> > > static void *vcpu_thread_main(void *data) {
> > > + struct perf_test_vcpu_args *vcpu_args;
> > > struct vcpu_thread *vcpu = data;
> > >
> > > + vcpu_args = &perf_test_args.vcpu_args[vcpu->vcpu_idx];
> > > +
> > > + if (perf_test_args.pin_vcpus)
> > > + pin_this_task_to_pcpu(vcpu_args->pcpu);
> > > +
> >
> > I think it would be better to do the thread pinning at the time when the
> > thread is created by providing a pthread_attr_t attr, e.g. :
> >
> > pthread_attr_t attr;
> >
> > CPU_SET(vcpu->pcpu, &cpu_set);
> > pthread_attr_setaffinity_np(&attr, sizeof(cpu_set_t), &cpu_set);
> > pthread_create(thread, attr,...);
> >
> > Also, pinning a vCPU thread to a pCPU is a general operation
> > which other users would need. I think we could make it more general and
> > put it to kvm_util.
>
> We could, but it taking advantage of the pinning functionality would require
> plumbing a command line option for every test, or alternatively adding partial
> command line parsing with a "hidden" global struct to kvm_selftest_init(), though
> handling error checking for a truly generic case would be a mess. Either way,
> extending pinning to other tests would require non-trivial effort, and can be
> done on top of this series.
>
> That said, it's also trival to extract the pinning helpers to common code, and I
> can't think of any reason not to do that straightaway.
>
> Vipin, any objection to squashing the below diff with patch 5?
>
Looks fine to me, I will send v7 with this change.
> > e.g. adding it to the helper function that I'm trying to create
>
> If we go this route in the future, we'd need to add a worker trampoline as the
> pinning needs to happen in the worker task itself to guarantee that the pinning
> takes effect before the worker does anything useful. That should be very doable.
>
> I do like the idea of extending __vcpu_thread_create(), but we can do that once
> __vcpu_thread_create() lands to avoid further delaying this series.
>
> ---
> .../selftests/kvm/dirty_log_perf_test.c | 7 ++-
> .../selftests/kvm/include/kvm_util_base.h | 4 ++
> .../selftests/kvm/include/perf_test_util.h | 8 +--
> tools/testing/selftests/kvm/lib/kvm_util.c | 54 ++++++++++++++++++
> .../selftests/kvm/lib/perf_test_util.c | 57 +------------------
> 5 files changed, 68 insertions(+), 62 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/dirty_log_perf_test.c b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> index 35504b36b126..a82fc51d57ca 100644
> --- a/tools/testing/selftests/kvm/dirty_log_perf_test.c
> +++ b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> @@ -471,8 +471,11 @@ int main(int argc, char *argv[])
> }
> }
>
> - if (pcpu_list)
> - perf_test_setup_pinning(pcpu_list, nr_vcpus);
> + if (pcpu_list) {
> + kvm_parse_vcpu_pinning(pcpu_list, perf_test_args.vcpu_to_pcpu,
> + nr_vcpus);
> + perf_test_args.pin_vcpus = true;
> + }
>
> TEST_ASSERT(p.iterations >= 2, "The test should have at least two iterations");
>
> diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
> index e42a09cd24a0..3bf2333ef95d 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util_base.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
> @@ -688,6 +688,10 @@ static inline struct kvm_vm *vm_create_with_one_vcpu(struct kvm_vcpu **vcpu,
>
> struct kvm_vcpu *vm_recreate_with_one_vcpu(struct kvm_vm *vm);
>
> +void kvm_pin_this_task_to_pcpu(uint32_t pcpu);
> +void kvm_parse_vcpu_pinning(const char *pcpus_string, uint32_t vcpu_to_pcpu[],
> + int nr_vcpus);
> +
> unsigned long vm_compute_max_gfn(struct kvm_vm *vm);
> unsigned int vm_calc_num_guest_pages(enum vm_guest_mode mode, size_t size);
> unsigned int vm_num_host_pages(enum vm_guest_mode mode, unsigned int num_guest_pages);
> diff --git a/tools/testing/selftests/kvm/include/perf_test_util.h b/tools/testing/selftests/kvm/include/perf_test_util.h
> index ccfe3b9dc6bd..85320e0640fc 100644
> --- a/tools/testing/selftests/kvm/include/perf_test_util.h
> +++ b/tools/testing/selftests/kvm/include/perf_test_util.h
> @@ -27,8 +27,6 @@ struct perf_test_vcpu_args {
> /* Only used by the host userspace part of the vCPU thread */
> struct kvm_vcpu *vcpu;
> int vcpu_idx;
> - /* The pCPU to which this vCPU is pinned. Only valid if pin_vcpus is true. */
> - uint32_t pcpu;
> };
>
> struct perf_test_args {
> @@ -43,8 +41,12 @@ struct perf_test_args {
> bool nested;
> /* True if all vCPUs are pinned to pCPUs */
> bool pin_vcpus;
> + /* The vCPU=>pCPU pinning map. Only valid if pin_vcpus is true. */
> + uint32_t vcpu_to_pcpu[KVM_MAX_VCPUS];
>
> struct perf_test_vcpu_args vcpu_args[KVM_MAX_VCPUS];
> +
> +
> };
>
> extern struct perf_test_args perf_test_args;
> @@ -64,6 +66,4 @@ void perf_test_guest_code(uint32_t vcpu_id);
> uint64_t perf_test_nested_pages(int nr_vcpus);
> void perf_test_setup_nested(struct kvm_vm *vm, int nr_vcpus, struct kvm_vcpu *vcpus[]);
>
> -void perf_test_setup_pinning(const char *pcpus_string, int nr_vcpus);
> -
> #endif /* SELFTEST_KVM_PERF_TEST_UTIL_H */
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index f1cb1627161f..8292af9d7660 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -11,6 +11,7 @@
> #include "processor.h"
>
> #include <assert.h>
> +#include <sched.h>
> #include <sys/mman.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> @@ -443,6 +444,59 @@ struct kvm_vcpu *vm_recreate_with_one_vcpu(struct kvm_vm *vm)
> return vm_vcpu_recreate(vm, 0);
> }
>
> +void kvm_pin_this_task_to_pcpu(uint32_t pcpu)
> +{
> + cpu_set_t mask;
> + int r;
> +
> + CPU_ZERO(&mask);
> + CPU_SET(pcpu, &mask);
> + r = sched_setaffinity(0, sizeof(mask), &mask);
> + TEST_ASSERT(!r, "sched_setaffinity() failed for pCPU '%u'.\n", pcpu);
> +}
> +
> +static uint32_t parse_pcpu(const char *cpu_str, const cpu_set_t *allowed_mask)
> +{
> + uint32_t pcpu = atoi_non_negative(cpu_str);
> +
> + TEST_ASSERT(CPU_ISSET(pcpu, allowed_mask),
> + "Not allowed to run on pCPU '%d', check cgroups?\n", pcpu);
> + return pcpu;
> +}
> +
> +void kvm_parse_vcpu_pinning(const char *pcpus_string, uint32_t vcpu_to_pcpu[],
> + int nr_vcpus)
> +{
> + cpu_set_t allowed_mask;
> + char *cpu, *cpu_list;
> + char delim[2] = ",";
> + int i, r;
> +
> + cpu_list = strdup(pcpus_string);
> + TEST_ASSERT(cpu_list, "strdup() allocation failed.\n");
> +
> + r = sched_getaffinity(0, sizeof(allowed_mask), &allowed_mask);
> + TEST_ASSERT(!r, "sched_getaffinity() failed");
> +
> + cpu = strtok(cpu_list, delim);
> +
> + /* 1. Get all pcpus for vcpus. */
> + for (i = 0; i < nr_vcpus; i++) {
> + TEST_ASSERT(cpu, "pCPU not provided for vCPU '%d'\n", i);
> + vcpu_to_pcpu[i] = parse_pcpu(cpu, &allowed_mask);
> + cpu = strtok(NULL, delim);
> + }
> +
> + /* 2. Check if the main worker needs to be pinned. */
> + if (cpu) {
> + kvm_pin_this_task_to_pcpu(parse_pcpu(cpu, &allowed_mask));
> + cpu = strtok(NULL, delim);
> + }
> +
> + TEST_ASSERT(!cpu, "pCPU list contains trailing garbage characters '%s'", cpu);
> + free(cpu_list);
> +}
> +
> /*
> * Userspace Memory Region Find
> *
> diff --git a/tools/testing/selftests/kvm/lib/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c
> index 520d1f896d61..1d133007d7de 100644
> --- a/tools/testing/selftests/kvm/lib/perf_test_util.c
> +++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
> @@ -5,7 +5,6 @@
> #define _GNU_SOURCE
>
> #include <inttypes.h>
> -#include <sched.h>
>
> #include "kvm_util.h"
> #include "perf_test_util.h"
> @@ -243,17 +242,6 @@ void __weak perf_test_setup_nested(struct kvm_vm *vm, int nr_vcpus, struct kvm_v
> exit(KSFT_SKIP);
> }
>
> -static void pin_this_task_to_pcpu(uint32_t pcpu)
> -{
> - cpu_set_t mask;
> - int r;
> -
> - CPU_ZERO(&mask);
> - CPU_SET(pcpu, &mask);
> - r = sched_setaffinity(0, sizeof(mask), &mask);
> - TEST_ASSERT(!r, "sched_setaffinity() failed for pCPU '%u'.\n", pcpu);
> -}
> -
> static void *vcpu_thread_main(void *data)
> {
> struct perf_test_vcpu_args *vcpu_args;
> @@ -262,7 +250,7 @@ static void *vcpu_thread_main(void *data)
> vcpu_args = &perf_test_args.vcpu_args[vcpu->vcpu_idx];
>
> if (perf_test_args.pin_vcpus)
> - pin_this_task_to_pcpu(vcpu_args->pcpu);
> + kvm_pin_this_task_to_pcpu(perf_test_args.vcpu_to_pcpu[vcpu->vcpu_idx]);
>
> WRITE_ONCE(vcpu->running, true);
>
> @@ -312,46 +300,3 @@ void perf_test_join_vcpu_threads(int nr_vcpus)
> for (i = 0; i < nr_vcpus; i++)
> pthread_join(vcpu_threads[i].thread, NULL);
> }
> -
> -static uint32_t parse_pcpu(const char *cpu_str, const cpu_set_t *allowed_mask)
> -{
> - uint32_t pcpu = atoi_non_negative(cpu_str);
> -
> - TEST_ASSERT(CPU_ISSET(pcpu, allowed_mask),
> - "Not allowed to run on pCPU '%d', check cgroups?\n", pcpu);
> - return pcpu;
> -}
> -
> -void perf_test_setup_pinning(const char *pcpus_string, int nr_vcpus)
> -{
> - cpu_set_t allowed_mask;
> - char *cpu, *cpu_list;
> - char delim[2] = ",";
> - int i, r;
> -
> - cpu_list = strdup(pcpus_string);
> - TEST_ASSERT(cpu_list, "strdup() allocation failed.\n");
> -
> - r = sched_getaffinity(0, sizeof(allowed_mask), &allowed_mask);
> - TEST_ASSERT(!r, "sched_getaffinity() failed");
> -
> - cpu = strtok(cpu_list, delim);
> -
> - /* 1. Get all pcpus for vcpus. */
> - for (i = 0; i < nr_vcpus; i++) {
> - TEST_ASSERT(cpu, "pCPU not provided for vCPU '%d'\n", i);
> - perf_test_args.vcpu_args[i].pcpu = parse_pcpu(cpu, &allowed_mask);
> - cpu = strtok(NULL, delim);
> - }
> -
> - perf_test_args.pin_vcpus = true;
> -
> - /* 2. Check if the main worker needs to be pinned. */
> - if (cpu) {
> - pin_this_task_to_pcpu(parse_pcpu(cpu, &allowed_mask));
> - cpu = strtok(NULL, delim);
> - }
> -
> - TEST_ASSERT(!cpu, "pCPU list contains trailing garbage characters '%s'", cpu);
> - free(cpu_list);
> -}
>
> base-commit: 076ac4ca97225d6b8698a9b066153b556e97be7c
> --
>
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