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KVM: selftests: randomize which pages are written vs read

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Randomize which pages are written vs read using the random number
generator.

Change the variable wr_fract and associated function calls to
write_percent that now operates as a percentage from 0 to 100 where X
means each page has an X% chance of being written. Change the -f
argument to -w to reflect the new variable semantics. Keep the same
default of 100% writes.

Population always uses 100% writes to ensure all memory is actually
populated and not just mapped to the zero page. The prevents expensive
copy-on-write faults from occurring during the dirty memory iterations
below, which would pollute the performance results.

Each vCPU calculates its own random seed by adding its index to the
seed provided.

Signed-off-by: Colton Lewis <coltonlewis@google.com>
Reviewed-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20221107182208.479157-4-coltonlewis@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Colton Lewis
2022-11-07 18:22:07 +00:00
committed by Sean Christopherson
parent f11aa24bdb
commit 6864c6442f
4 changed files with 36 additions and 20 deletions
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2
tools/testing/selftests/kvm/access_tracking_perf_test.c
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@@ -279,7 +279,7 @@ static void run_iteration(struct kvm_vm *vm, int nr_vcpus, const char *descripti
static void access_memory(struct kvm_vm *vm, int nr_vcpus,
enum access_type access, const char *description)
{
perf_test_set_wr_fract(vm, (access == ACCESS_READ) ? INT_MAX : 1);
perf_test_set_write_percent(vm, (access == ACCESS_READ) ? 0 : 100);
iteration_work = ITERATION_ACCESS_MEMORY;
run_iteration(vm, nr_vcpus, description);
}