Re: [PATCH 0/4] KVM: selftests: Avoid mmap_sem contention during memory population

[Paolo Bonzini <pbonzini@redhat.com>]

On 11/11/21 01:12, David Matlack wrote:
> This series fixes a performance issue in the KVM selftests, specifically
> those that use perf_test_util. These tests create vCPU threads which
> immediately enter guest mode and start faulting in memory. Creating
> vCPU threads while faulting in memory is a recipe for generating a lot
> of contention on the mmap_sem, as thread creation requires acquiring the
> mmap_sem in write mode.
> 
> This series fixes this issue by ensuring that all vCPUs threads are
> created before entering guest mode. As part of fixing this issue I
> consolidated the code to create and join vCPU threads across all users
> of perf_test_util.
> 
> The last commit is an unrelated perf_test_util cleanup.
> 
> Note: This series applies on top of
> https://lore.kernel.org/kvm/20211111000310.1435032-1-dmatlack@google.com/,
> although the dependency on the series is just cosmetic.
> 
> David Matlack (4):
>    KVM: selftests: Start at iteration 0 instead of -1
>    KVM: selftests: Move vCPU thread creation and joining to common
>      helpers
>    KVM: selftests: Wait for all vCPU to be created before entering guest
>      mode
>    KVM: selftests: Use perf_test_destroy_vm in
>      memslot_modification_stress_test
> 
>   .../selftests/kvm/access_tracking_perf_test.c | 46 +++---------
>   .../selftests/kvm/demand_paging_test.c        | 25 +------
>   .../selftests/kvm/dirty_log_perf_test.c       | 19 ++---
>   .../selftests/kvm/include/perf_test_util.h    |  5 ++
>   .../selftests/kvm/lib/perf_test_util.c        | 72 +++++++++++++++++++
>   .../kvm/memslot_modification_stress_test.c    | 25 ++-----
>   6 files changed, 96 insertions(+), 96 deletions(-)
> 

Queued, thanks.

Paolo