linux-kernel - Re: [PATCH V5 0/2] selftests: KVM: Add a test for eager page splitting

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Message-ID: <CABgObfaP7P7fk66-EGF-zPEk0H14u3YkM42FRXrEvU=hwFSYgg@mail.gmail.com>
Date:   Tue, 14 Mar 2023 14:27:55 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Ben Gardon <bgardon@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Vipin Sharma <vipinsh@...gle.com>,
        Ricardo Koller <ricarkol@...gle.com>
Subject: Re: [PATCH V5 0/2] selftests: KVM: Add a test for eager page splitting

On Tue, Jan 31, 2023 at 7:18 PM Ben Gardon <bgardon@...gle.com> wrote:
>
> David Matlack recently added a feature known as eager page splitting
> to x86 KVM. This feature improves vCPU performance during dirty
> logging because the splitting operation is moved out of the page
> fault path, avoiding EPT/NPT violations or allowing the vCPU threads
> to resolve the violation in the fast path.
>
> While this feature is a great performance improvement, it does not
> have adequate testing in KVM selftests. Add a test to provide coverage
> of eager page splitting.
>
> Patch 1 is a quick refactor to be able to re-use some code from
> dirty_log_perf_test.
> Patch 2 adds the actual test.

I have finally queued it, but made a small change to allow running it
with non-hugetlbfs page types.

Also, see the "KVM: selftests: skip hugetlb tests if huge pages are
not available" patch I have just sent, which makes the test not fail
in a default kernel configuration.

Thanks,

Paolo