linux-kernel - RE: [PATCH v5 0/5] dirty_log_perf

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Date:   Fri, 14 Oct 2022 15:12:20 +0000
From:   "Wang, Wei W" <wei.w.wang@...el.com>
To:     Vipin Sharma <vipinsh@...gle.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>
CC:     "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 v5 0/5] dirty_log_perf_test vCPU pinning

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?

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