2021-01-13 02:46:44

by Ben Gardon

Subject: [PATCH 2/6] KVM: selftests: Avoid flooding debug log while populating memory

Peter Xu pointed out that a log message printed while waiting for the
memory population phase of the dirty_log_perf_test will flood the debug
logs as there is no delay after printing the message. Since the message
does not provide much value anyway, remove it.

Reviewed-by: Jacob Xu <[email protected]>

Signed-off-by: Ben Gardon <[email protected]>
---
tools/testing/selftests/kvm/dirty_log_perf_test.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/kvm/dirty_log_perf_test.c b/tools/testing/selftests/kvm/dirty_log_perf_test.c
index 16efe6589b43..15a9c45bdb5f 100644
--- a/tools/testing/selftests/kvm/dirty_log_perf_test.c
+++ b/tools/testing/selftests/kvm/dirty_log_perf_test.c
@@ -146,8 +146,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
/* Allow the vCPU to populate memory */
pr_debug("Starting iteration %lu - Populating\n", iteration);
while (READ_ONCE(vcpu_last_completed_iteration[vcpu_id]) != iteration)
- pr_debug("Waiting for vcpu_last_completed_iteration == %lu\n",
- iteration);
+ ;

ts_diff = timespec_elapsed(start);
pr_info("Populate memory time: %ld.%.9lds\n",
@@ -171,9 +170,9 @@ static void run_test(enum vm_guest_mode mode, void *arg)

pr_debug("Starting iteration %lu\n", iteration);
for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++) {
- while (READ_ONCE(vcpu_last_completed_iteration[vcpu_id]) != iteration)
- pr_debug("Waiting for vCPU %d vcpu_last_completed_iteration == %lu\n",
- vcpu_id, iteration);
+ while (READ_ONCE(vcpu_last_completed_iteration[vcpu_id])
+ != iteration)
+ ;
}

ts_diff = timespec_elapsed(start);
--
2.30.0.284.gd98b1dd5eaa7-goog

2021-01-13 07:41:14

by Thomas Huth

Subject: Re: [PATCH 2/6] KVM: selftests: Avoid flooding debug log while populating memory

On 12/01/2021 22.42, Ben Gardon wrote:
> Peter Xu pointed out that a log message printed while waiting for the
> memory population phase of the dirty_log_perf_test will flood the debug
> logs as there is no delay after printing the message. Since the message
> does not provide much value anyway, remove it.
>
> Reviewed-by: Jacob Xu <[email protected]>
>
> Signed-off-by: Ben Gardon <[email protected]>
> ---
> tools/testing/selftests/kvm/dirty_log_perf_test.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/dirty_log_perf_test.c b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> index 16efe6589b43..15a9c45bdb5f 100644
> --- a/tools/testing/selftests/kvm/dirty_log_perf_test.c
> +++ b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> @@ -146,8 +146,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> /* Allow the vCPU to populate memory */
> pr_debug("Starting iteration %lu - Populating\n", iteration);
> while (READ_ONCE(vcpu_last_completed_iteration[vcpu_id]) != iteration)
> - pr_debug("Waiting for vcpu_last_completed_iteration == %lu\n",
> - iteration);
> + ;
>
> ts_diff = timespec_elapsed(start);
> pr_info("Populate memory time: %ld.%.9lds\n",
> @@ -171,9 +170,9 @@ static void run_test(enum vm_guest_mode mode, void *arg)
>
> pr_debug("Starting iteration %lu\n", iteration);
> for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++) {
> - while (READ_ONCE(vcpu_last_completed_iteration[vcpu_id]) != iteration)
> - pr_debug("Waiting for vCPU %d vcpu_last_completed_iteration == %lu\n",
> - vcpu_id, iteration);
> + while (READ_ONCE(vcpu_last_completed_iteration[vcpu_id])
> + != iteration)
> + ;
> }
>
> ts_diff = timespec_elapsed(start);
>

Reviewed-by: Thomas Huth <[email protected]>

2021-01-16 00:03:26

by Sean Christopherson

Subject: Re: [PATCH 2/6] KVM: selftests: Avoid flooding debug log while populating memory

On Tue, Jan 12, 2021, Ben Gardon wrote:
> Peter Xu pointed out that a log message printed while waiting for the
> memory population phase of the dirty_log_perf_test will flood the debug
> logs as there is no delay after printing the message. Since the message
> does not provide much value anyway, remove it.

Does it provide value if something goes wrong? E.g. if a vCPU doesn't finish,
how would one go about debugging? Would it make sense to make the print
ratelimited instead of removing it altogether?

> Reviewed-by: Jacob Xu <[email protected]>
>
> Signed-off-by: Ben Gardon <[email protected]>
> ---
> tools/testing/selftests/kvm/dirty_log_perf_test.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/dirty_log_perf_test.c b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> index 16efe6589b43..15a9c45bdb5f 100644
> --- a/tools/testing/selftests/kvm/dirty_log_perf_test.c
> +++ b/tools/testing/selftests/kvm/dirty_log_perf_test.c
> @@ -146,8 +146,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
> /* Allow the vCPU to populate memory */
> pr_debug("Starting iteration %lu - Populating\n", iteration);
> while (READ_ONCE(vcpu_last_completed_iteration[vcpu_id]) != iteration)
> - pr_debug("Waiting for vcpu_last_completed_iteration == %lu\n",
> - iteration);
> + ;
>
> ts_diff = timespec_elapsed(start);
> pr_info("Populate memory time: %ld.%.9lds\n",
> @@ -171,9 +170,9 @@ static void run_test(enum vm_guest_mode mode, void *arg)
>
> pr_debug("Starting iteration %lu\n", iteration);
> for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++) {
> - while (READ_ONCE(vcpu_last_completed_iteration[vcpu_id]) != iteration)
> - pr_debug("Waiting for vCPU %d vcpu_last_completed_iteration == %lu\n",
> - vcpu_id, iteration);
> + while (READ_ONCE(vcpu_last_completed_iteration[vcpu_id])
> + != iteration)

I like the original better. Poking out past 80 chars isn't the end of the world.

> + ;
> }
>
> ts_diff = timespec_elapsed(start);
> --
> 2.30.0.284.gd98b1dd5eaa7-goog
>