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Date: Wed, 21 Sep 2022 12:02:11 -0700
From: David Matlack <dmatlack@...gle.com>
To: Vipin Sharma <vipinsh@...gle.com>
Cc: seanjc@...gle.com, pbonzini@...hat.com, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/4] KVM: selftests: Run dirty_log_perf_test on
specific cpus
On Fri, Aug 26, 2022 at 11:45:00AM -0700, Vipin Sharma wrote:
> Add command line options, -c, to run the vcpus and optionally the main
> process on the specific cpus on a host machine. This is useful as it
> provides a way to analyze performance based on the vcpus and dirty log
> worker locations, like on the different numa nodes or on the same numa
> nodes.
>
> Link: https://lore.kernel.org/lkml/20220801151928.270380-1-vipinsh@google.com
> Signed-off-by: Vipin Sharma <vipinsh@...gle.com>
> Suggested-by: David Matlack <dmatlack@...gle.com>
> Suggested-by: Sean Christopherson <seanjc@...gle.com>
> Suggested-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
> .../selftests/kvm/dirty_log_perf_test.c | 23 ++++++-
> .../selftests/kvm/include/perf_test_util.h | 4 ++
> .../selftests/kvm/lib/perf_test_util.c | 62 ++++++++++++++++++-
> 3 files changed, 86 insertions(+), 3 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/dirty_log_perf_test.c b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> index 1346f6b5a9bd..9514b5f28b67 100644
> --- a/tools/testing/selftests/kvm/dirty_log_perf_test.c
> +++ b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> @@ -353,7 +353,7 @@ static void help(char *name)
> puts("");
> printf("usage: %s [-h] [-i iterations] [-p offset] [-g] "
> "[-m mode] [-n] [-b vcpu bytes] [-v vcpus] [-o] [-s mem type]"
> - "[-x memslots]\n", name);
> + "[-x memslots] [-c physical cpus to run test on]\n", name);
> puts("");
> printf(" -i: specify iteration counts (default: %"PRIu64")\n",
> TEST_HOST_LOOP_N);
> @@ -383,6 +383,18 @@ static void help(char *name)
> backing_src_help("-s");
> printf(" -x: Split the memory region into this number of memslots.\n"
> " (default: 1)\n");
> + printf(" -c: Comma separated values of the physical CPUs, which will run\n"
> + " the vCPUs, optionally, followed by the main application thread cpu.\n"
> + " Number of values must be at least the number of vCPUs.\n"
> + " The very next number is used to pin main application thread.\n\n"
> + " Example: ./dirty_log_perf_test -v 3 -c 22,23,24,50\n"
> + " This means that the vcpu 0 will run on the physical cpu 22,\n"
> + " vcpu 1 on the physical cpu 23, vcpu 2 on the physical cpu 24\n"
> + " and the main thread will run on cpu 50.\n\n"
> + " Example: ./dirty_log_perf_test -v 3 -c 22,23,24\n"
> + " Same as the previous example except now main application\n"
> + " thread can run on any physical cpu\n\n"
> + " (default: No cpu mapping)\n");
> puts("");
> exit(0);
> }
> @@ -398,6 +410,7 @@ int main(int argc, char *argv[])
> .slots = 1,
> };
> int opt;
> + const char *pcpu_list = NULL;
>
> dirty_log_manual_caps =
> kvm_check_cap(KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2);
> @@ -406,11 +419,14 @@ int main(int argc, char *argv[])
>
> guest_modes_append_default();
>
> - while ((opt = getopt(argc, argv, "b:ef:ghi:m:nop:s:v:x:")) != -1) {
> + while ((opt = getopt(argc, argv, "b:c:ef:ghi:m:nop:s:v:x:")) != -1) {
> switch (opt) {
> case 'b':
> guest_percpu_mem_size = parse_size(optarg);
> break;
> + case 'c':
> + pcpu_list = optarg;
> + break;
> case 'e':
> /* 'e' is for evil. */
> run_vcpus_while_disabling_dirty_logging = true;
> @@ -459,6 +475,9 @@ int main(int argc, char *argv[])
> }
> }
>
> + if (pcpu_list)
> + perf_test_setup_pinning(pcpu_list, nr_vcpus);
> +
> TEST_ASSERT(p.iterations >= 2, "The test should have at least two iterations");
>
> pr_info("Test iterations: %"PRIu64"\n", p.iterations);
> diff --git a/tools/testing/selftests/kvm/include/perf_test_util.h b/tools/testing/selftests/kvm/include/perf_test_util.h
> index eaa88df0555a..d02619f153a2 100644
> --- a/tools/testing/selftests/kvm/include/perf_test_util.h
> +++ b/tools/testing/selftests/kvm/include/perf_test_util.h
> @@ -27,6 +27,8 @@ struct perf_test_vcpu_args {
> /* Only used by the host userspace part of the vCPU thread */
> struct kvm_vcpu *vcpu;
> int vcpu_idx;
> + bool pin_pcpu;
> + int pcpu;
> };
>
> struct perf_test_args {
> @@ -60,4 +62,6 @@ 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[]);
>
> +int 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/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c
> index 9618b37c66f7..7a1e8223e7c7 100644
> --- a/tools/testing/selftests/kvm/lib/perf_test_util.c
> +++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
> @@ -2,7 +2,10 @@
> /*
> * Copyright (C) 2020, Google LLC.
> */
> +#define _GNU_SOURCE
> +
> #include <inttypes.h>
> +#include <sched.h>
>
> #include "kvm_util.h"
> #include "perf_test_util.h"
> @@ -240,9 +243,26 @@ void __weak perf_test_setup_nested(struct kvm_vm *vm, int nr_vcpus, struct kvm_v
> exit(KSFT_SKIP);
> }
>
> +static void pin_me_to_pcpu(int pcpu)
> +{
> + cpu_set_t cpuset;
> + int err;
> +
> + CPU_ZERO(&cpuset);
> + CPU_SET(pcpu, &cpuset);
> + errno = 0;
No need to set errno explicitly here since sched_setaffinity() is
defined to set errno if it returns -1.
> + err = sched_setaffinity(0, sizeof(cpu_set_t), &cpuset);
> + TEST_ASSERT(err == 0, "sched_setaffinity errored out: %d\n", errno);
TEST_ASSERT() already prints errno. It would be more useful to print
@pcpu to help the user debug the failure.
Also, use "()" after function names.
> +}
> +
> static void *vcpu_thread_main(void *data)
> {
> struct vcpu_thread *vcpu = data;
> + int idx = vcpu->vcpu_idx;
> + struct perf_test_vcpu_args *vcpu_args = &perf_test_args.vcpu_args[idx];
> +
> + if (vcpu_args->pin_pcpu)
> + pin_me_to_pcpu(vcpu_args->pcpu);
>
> WRITE_ONCE(vcpu->running, true);
>
> @@ -255,7 +275,7 @@ static void *vcpu_thread_main(void *data)
> while (!READ_ONCE(all_vcpu_threads_running))
> ;
>
> - vcpu_thread_fn(&perf_test_args.vcpu_args[vcpu->vcpu_idx]);
> + vcpu_thread_fn(vcpu_args);
>
> return NULL;
> }
> @@ -292,3 +312,43 @@ void perf_test_join_vcpu_threads(int nr_vcpus)
> for (i = 0; i < nr_vcpus; i++)
> pthread_join(vcpu_threads[i].thread, NULL);
> }
> +
> +int perf_test_setup_pinning(const char *pcpus_string, int nr_vcpus)
> +{
> + char delim[2] = ",";
> + char *cpu, *cpu_list;
> + int i = 0, pcpu_num;
> +
> + cpu_list = strdup(pcpus_string);
> + TEST_ASSERT(cpu_list, "strdup() allocation failed.\n");
> +
> + cpu = strtok(cpu_list, delim);
> +
> + // 1. Get all pcpus for vcpus
> + while (cpu && i < nr_vcpus) {
> + pcpu_num = atoi_paranoid(cpu);
> + TEST_ASSERT(pcpu_num >= 0, "Invalid cpu number: %d\n", pcpu_num);
> +
> + perf_test_args.vcpu_args[i].pin_pcpu = true;
Since pinning vCPU is all or nothing, this can be a single bool instead
of per-vCPUs.
/* True if vCPUs are pinned to pCPUs. */
perf_test_args.pin_vcpus
/* The pCPU to which this vCPU is pinned. Only valid if pin_vcpus is true. */
perf_test_args.vcpus_args[i].pcpu
> + perf_test_args.vcpu_args[i++].pcpu = pcpu_num;
> +
> + cpu = strtok(NULL, delim);
> + }
> +
> + TEST_ASSERT(i == nr_vcpus,
> + "Number of pcpus (%d) not sufficient for the number of vcpus (%d).",
> + i, nr_vcpus);
> +
> + // 2. Check if main worker is provided
> + if (cpu) {
> + pcpu_num = atoi_paranoid(cpu);
> + TEST_ASSERT(pcpu_num >= 0, "Invalid cpu number: %d\n", pcpu_num);
nite: Create a helper function for this since it's repeated twice.
> +
> + pin_me_to_pcpu(pcpu_num);
> +
> + cpu = strtok(NULL, delim);
Delete?
> + }
> +
> + free(cpu_list);
> + return i;
The return value is unused. Drop it until we have a usecase for it.
> +}
> --
> 2.37.2.672.g94769d06f0-goog
>
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