| Message ID | 20240619182128.4131355-3-dapeng1.mi@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM vPMU code refine | expand |
On Thu, Jun 20, 2024, Dapeng Mi wrote: > Huge number of "Random seed:" messages are printed when running > pmu_counters_test. It leads to the regular test output is totally > flooded by these over-verbose messages. > > Downgrade "Random seed" message printing level to debug and prevent it > to be printed in normal case. I completely agree this is annoying, but the whole point of printing the seed is so that the seed is automatically captured if a test fails, e.g. so that the failure can be reproduced if it is dependent on some random decision. Rather than simply hiding the message, what if print the seed if and only if it changes? -- From: Sean Christopherson <seanjc@google.com> Date: Thu, 20 Jun 2024 10:29:53 -0700 Subject: [PATCH] KVM: selftests: Print the seed for the guest pRNG iff it has changed Print the guest's random seed during VM creation if and only if the seed has changed since the seed was last printed. The vast majority of tests, if not all tests at this point, set the seed during test initialization and never change the seed, i.e. printing it every time a VM is created is useless noise. Snapshot and print the seed during early selftest init to play nice with tests that use the kselftests harness, at the cost of printing an unused seed for tests that change the seed during test-specific initialization, e.g. dirty_log_perf_test. The kselftests harness runs each testcase in a separate process that is forked from the original process before creating each testcase's VM, i.e. waiting until first VM creation will result in the seed being printed by each testcase despite it never changing. And long term, the hope/goal is that setting the seed will be handled by the core framework, i.e. that the dirty_log_perf_test wart will naturally go away. Reported-by: Yi Lai <yi1.lai@intel.com> Reported-by: Dapeng Mi <dapeng1.mi@linux.intel.com> Signed-off-by: Sean Christopherson <seanjc@google.com> --- tools/testing/selftests/kvm/lib/kvm_util.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c index ad00e4761886..56b170b725b3 100644 --- a/tools/testing/selftests/kvm/lib/kvm_util.c +++ b/tools/testing/selftests/kvm/lib/kvm_util.c @@ -21,6 +21,7 @@ uint32_t guest_random_seed; struct guest_random_state guest_rng; +static uint32_t last_guest_seed; static int vcpu_mmap_sz(void); @@ -434,7 +435,10 @@ struct kvm_vm *__vm_create(struct vm_shape shape, uint32_t nr_runnable_vcpus, slot0 = memslot2region(vm, 0); ucall_init(vm, slot0->region.guest_phys_addr + slot0->region.memory_size); - pr_info("Random seed: 0x%x\n", guest_random_seed); + if (guest_random_seed != last_guest_seed) { + pr_info("Random seed: 0x%x\n", guest_random_seed); + last_guest_seed = guest_random_seed; + } guest_rng = new_guest_random_state(guest_random_seed); sync_global_to_guest(vm, guest_rng); @@ -2319,7 +2323,8 @@ void __attribute((constructor)) kvm_selftest_init(void) /* Tell stdout not to buffer its content. */ setbuf(stdout, NULL); - guest_random_seed = random(); + guest_random_seed = last_guest_seed = random(); + pr_info("Random seed: 0x%x\n", guest_random_seed); kvm_selftest_arch_init(); } base-commit: c81b138d5075c6f5ba3419ac1d2a2e7047719c14 --
On 6/21/2024 2:13 AM, Sean Christopherson wrote: > On Thu, Jun 20, 2024, Dapeng Mi wrote: >> Huge number of "Random seed:" messages are printed when running >> pmu_counters_test. It leads to the regular test output is totally >> flooded by these over-verbose messages. >> >> Downgrade "Random seed" message printing level to debug and prevent it >> to be printed in normal case. > I completely agree this is annoying, but the whole point of printing the seed is > so that the seed is automatically captured if a test fails, e.g. so that the > failure can be reproduced if it is dependent on some random decision. > > Rather than simply hiding the message, what if print the seed if and only if it > changes? Yeah, it's indeed better. > > -- > From: Sean Christopherson <seanjc@google.com> > Date: Thu, 20 Jun 2024 10:29:53 -0700 > Subject: [PATCH] KVM: selftests: Print the seed for the guest pRNG iff it has > changed s/iff/if/ > > Print the guest's random seed during VM creation if and only if the seed > has changed since the seed was last printed. The vast majority of tests, > if not all tests at this point, set the seed during test initialization > and never change the seed, i.e. printing it every time a VM is created is > useless noise. > > Snapshot and print the seed during early selftest init to play nice with > tests that use the kselftests harness, at the cost of printing an unused > seed for tests that change the seed during test-specific initialization, > e.g. dirty_log_perf_test. The kselftests harness runs each testcase in a > separate process that is forked from the original process before creating > each testcase's VM, i.e. waiting until first VM creation will result in > the seed being printed by each testcase despite it never changing. And > long term, the hope/goal is that setting the seed will be handled by the > core framework, i.e. that the dirty_log_perf_test wart will naturally go > away. > > Reported-by: Yi Lai <yi1.lai@intel.com> > Reported-by: Dapeng Mi <dapeng1.mi@linux.intel.com> > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > tools/testing/selftests/kvm/lib/kvm_util.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c > index ad00e4761886..56b170b725b3 100644 > --- a/tools/testing/selftests/kvm/lib/kvm_util.c > +++ b/tools/testing/selftests/kvm/lib/kvm_util.c > @@ -21,6 +21,7 @@ > > uint32_t guest_random_seed; > struct guest_random_state guest_rng; > +static uint32_t last_guest_seed; > > static int vcpu_mmap_sz(void); > > @@ -434,7 +435,10 @@ struct kvm_vm *__vm_create(struct vm_shape shape, uint32_t nr_runnable_vcpus, > slot0 = memslot2region(vm, 0); > ucall_init(vm, slot0->region.guest_phys_addr + slot0->region.memory_size); > > - pr_info("Random seed: 0x%x\n", guest_random_seed); > + if (guest_random_seed != last_guest_seed) { > + pr_info("Random seed: 0x%x\n", guest_random_seed); > + last_guest_seed = guest_random_seed; > + } > guest_rng = new_guest_random_state(guest_random_seed); > sync_global_to_guest(vm, guest_rng); > > @@ -2319,7 +2323,8 @@ void __attribute((constructor)) kvm_selftest_init(void) > /* Tell stdout not to buffer its content. */ > setbuf(stdout, NULL); > > - guest_random_seed = random(); > + guest_random_seed = last_guest_seed = random(); > + pr_info("Random seed: 0x%x\n", guest_random_seed); > > kvm_selftest_arch_init(); > } > > base-commit: c81b138d5075c6f5ba3419ac1d2a2e7047719c14
On Fri, Jun 21, 2024, Dapeng Mi wrote: > > -- > > From: Sean Christopherson <seanjc@google.com> > > Date: Thu, 20 Jun 2024 10:29:53 -0700 > > Subject: [PATCH] KVM: selftests: Print the seed for the guest pRNG iff it has > > changed > > s/iff/if/ "iff" is shorthand for "if and only if". I try to write out the full "if and only if" when possible, but use "iff" in shortlogs when I want to squeeze in more words.
On 6/21/2024 9:29 PM, Sean Christopherson wrote: > On Fri, Jun 21, 2024, Dapeng Mi wrote: >>> -- >>> From: Sean Christopherson <seanjc@google.com> >>> Date: Thu, 20 Jun 2024 10:29:53 -0700 >>> Subject: [PATCH] KVM: selftests: Print the seed for the guest pRNG iff it has >>> changed >> s/iff/if/ > "iff" is shorthand for "if and only if". I try to write out the full "if and only > if" when possible, but use "iff" in shortlogs when I want to squeeze in more words. Good to know. Thanks.
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c index ad00e4761886..8568c7d619c3 100644 --- a/tools/testing/selftests/kvm/lib/kvm_util.c +++ b/tools/testing/selftests/kvm/lib/kvm_util.c @@ -434,7 +434,7 @@ struct kvm_vm *__vm_create(struct vm_shape shape, uint32_t nr_runnable_vcpus, slot0 = memslot2region(vm, 0); ucall_init(vm, slot0->region.guest_phys_addr + slot0->region.memory_size); - pr_info("Random seed: 0x%x\n", guest_random_seed); + pr_debug("Random seed: 0x%x\n", guest_random_seed); guest_rng = new_guest_random_state(guest_random_seed); sync_global_to_guest(vm, guest_rng);
Huge number of "Random seed:" messages are printed when running pmu_counters_test. It leads to the regular test output is totally flooded by these over-verbose messages. Downgrade "Random seed" message printing level to debug and prevent it to be printed in normal case. Reported-by: Yi Lai <yi1.lai@intel.com> Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com> --- tools/testing/selftests/kvm/lib/kvm_util.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)