From: Ricardo Koller <ricarkol@google.com>
To: Colton Lewis <coltonlewis@google.com>
Cc: kvm@vger.kernel.org, pbonzini@redhat.com, maz@kernel.org,
dmatlack@google.com, seanjc@google.com, bgardon@google.com,
oupton@google.com
Subject: Re: [PATCH 1/3] KVM: selftests: Allocate additional space for latency samples
Date: Tue, 17 Jan 2023 12:32:43 -0800 [thread overview]
Message-ID: <Y8cF65zpxOlYkAUl@google.com> (raw)
In-Reply-To: <20221115173258.2530923-2-coltonlewis@google.com>
Hi Colton,
On Tue, Nov 15, 2022 at 05:32:56PM +0000, Colton Lewis wrote:
> Allocate additional space for latency samples. This has been separated
> out to call attention to the additional VM memory allocation. The test
> runs out of physical pages without the additional allocation. The 100
> multiple for pages was determined by trial and error. A more
> well-reasoned calculation would be preferable.
>
> Signed-off-by: Colton Lewis <coltonlewis@google.com>
> ---
> tools/testing/selftests/kvm/lib/perf_test_util.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/lib/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c
> index 137be359b09e..a48904b64e19 100644
> --- a/tools/testing/selftests/kvm/lib/perf_test_util.c
> +++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
> @@ -38,6 +38,12 @@ static bool all_vcpu_threads_running;
>
> static struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
>
> +#define SAMPLES_PER_VCPU 1000
> +#define SAMPLE_CAPACITY (SAMPLES_PER_VCPU * KVM_MAX_VCPUS)
> +
> +/* Store all samples in a flat array so they can be easily sorted later. */
> +uint64_t latency_samples[SAMPLE_CAPACITY];
> +
> /*
> * Continuously write to the first 8 bytes of each page in the
> * specified region.
> @@ -122,7 +128,7 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int nr_vcpus,
> {
> struct perf_test_args *pta = &perf_test_args;
> struct kvm_vm *vm;
> - uint64_t guest_num_pages, slot0_pages = 0;
> + uint64_t guest_num_pages, sample_pages, slot0_pages = 0;
> uint64_t backing_src_pagesz = get_backing_src_pagesz(backing_src);
> uint64_t region_end_gfn;
> int i;
> @@ -161,7 +167,9 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int nr_vcpus,
> * The memory is also added to memslot 0, but that's a benign side
> * effect as KVM allows aliasing HVAs in meslots.
> */
> - vm = __vm_create_with_vcpus(mode, nr_vcpus, slot0_pages + guest_num_pages,
> + sample_pages = 100 * sizeof(latency_samples) / pta->guest_page_size;
I don't think there's any need to guess. The number of accesses is
vcpu_args->pages (one access per guest page). So all memory could be
allocated dynamically to hold "vcpu_args->pages * sample_sz".
> + vm = __vm_create_with_vcpus(mode, nr_vcpus,
> + slot0_pages + guest_num_pages + sample_pages,
> perf_test_guest_code, vcpus);
>
> pta->vm = vm;
> --
> 2.38.1.431.g37b22c650d-goog
>
Thanks,
Ricardo
next prev parent reply other threads:[~2023-01-17 22:11 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-15 17:32 [PATCH 0/3] Calculate memory access latency stats Colton Lewis
2022-11-15 17:32 ` [PATCH 1/3] KVM: selftests: Allocate additional space for latency samples Colton Lewis
2023-01-17 20:32 ` Ricardo Koller [this message]
2023-01-18 16:49 ` Sean Christopherson
2023-01-26 18:00 ` Colton Lewis
2022-11-15 17:32 ` [PATCH 2/3] KVM: selftests: Collect memory access " Colton Lewis
2023-01-17 20:43 ` Ricardo Koller
2023-01-18 16:32 ` Sean Christopherson
2023-01-26 18:00 ` Colton Lewis
2023-01-26 19:07 ` Sean Christopherson
2023-01-26 17:58 ` Colton Lewis
2023-01-26 18:30 ` Ricardo Koller
2023-01-17 20:48 ` Ricardo Koller
2023-01-26 17:59 ` Colton Lewis
2022-11-15 17:32 ` [PATCH 3/3] KVM: selftests: Print summary stats of memory latency distribution Colton Lewis
2023-01-17 20:45 ` Ricardo Koller
2023-01-26 17:58 ` Colton Lewis
2023-01-18 16:43 ` Sean Christopherson
2023-01-26 17:59 ` Colton Lewis
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