KVM: selftests: Improvements on dirty-ring [LWN.net]

From:		Leonardo Bras <leo.bras-AT-arm.com>
To:		Paolo Bonzini <pbonzini-AT-redhat.com>, Shuah Khan <shuah-AT-kernel.org>, Sean Christopherson <seanjc-AT-google.com>, David Matlack <dmatlack-AT-google.com>, Leonardo Bras <leo.bras-AT-arm.com>, Ackerley Tng <ackerleytng-AT-google.com>, Oliver Upton <oupton-AT-kernel.org>, Marc Zyngier <maz-AT-kernel.org>, Wu Fei <wu.fei9-AT-sanechips.com.cn>, Steffen Eiden <seiden-AT-linux.ibm.com>, Claudio Imbrenda <imbrenda-AT-linux.ibm.com>
Subject:		[RFC PATCH v2 0/3] KVM: selftests: Improvements on dirty-ring
Date:		Mon, 29 Jun 2026 11:59:39 +0100
Message-ID:		<20260629105950.1790259-1-leo.bras@arm.com>
Cc:		kvm-AT-vger.kernel.org, linux-kselftest-AT-vger.kernel.org, linux-kernel-AT-vger.kernel.org
Archive-link:		Article


Add support to dirty-ring on dirty_log_perf_test, so we can measure
performance differences when we change / improve the mechanism.

One major conflict I had in this set is that dirty-ring needs to be 
enabled after the VM was created, but before any cpu is created, so
for that, I made a few changes on memstress so it can actually take
dirty-ring size as a parameter for VM creation. (Patch #1)
I honestly don't think it's pretty, but I could not think on a
better way of doing this without messing too much in the code.

Also added some checks in dirty-ring enable, so an error message on
ring size is more informative.

Please provide feedback :)

Thanks!
Leo


Changes since RFCv1:
- Stuff reported by Sashiko
  - Fixed elements / byte size wrapping issue
  - Removed element count due to concurrency
  - Testing exit_reason instead of ioctl return value
  - Some nits
Link: https://lore.kernel.org/all/20260624171656.1737580-1-leo....

Leonardo Bras (3):
  KVM: selftests: memstress: Add option to enable dirty-ring on VM
    creation
  KVM: selftests: Check dirty-ring size before enabling
  KVM: selftests: dirty_log_perf_test: Add dirty-ring support

 .../testing/selftests/kvm/include/memstress.h |  3 +-
 .../selftests/kvm/access_tracking_perf_test.c |  2 +-
 .../selftests/kvm/demand_paging_test.c        |  2 +-
 .../selftests/kvm/dirty_log_perf_test.c       | 95 +++++++++++++++++--
 tools/testing/selftests/kvm/lib/kvm_util.c    | 19 +++-
 tools/testing/selftests/kvm/lib/memstress.c   | 34 ++++++-
 .../kvm/memslot_modification_stress_test.c    |  2 +-
 .../kvm/x86/dirty_log_page_splitting_test.c   |  2 +-
 8 files changed, 137 insertions(+), 22 deletions(-)


base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
-- 
2.54.0