linux-kernel - Re: [PATCH v4 08/10] KVM: selftests: Time guest demand paging

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Date:   Fri, 24 Jan 2020 11:21:03 +0100
From:   Andrew Jones <drjones@...hat.com>
To:     Ben Gardon <bgardon@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Cannon Matthews <cannonmatthews@...gle.com>,
        Peter Xu <peterx@...hat.com>, Peter Shier <pshier@...gle.com>,
        Oliver Upton <oupton@...gle.com>
Subject: Re: [PATCH v4 08/10] KVM: selftests: Time guest demand paging

On Thu, Jan 23, 2020 at 10:04:34AM -0800, Ben Gardon wrote:
> In order to quantify demand paging performance, time guest execution
> during demand paging.
> 
> Signed-off-by: Ben Gardon <bgardon@...gle.com>
> ---
>  .../selftests/kvm/demand_paging_test.c        | 68 +++++++++++++++++++
>  1 file changed, 68 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
> index 2002032df32cc..0dc5d04718678 100644
> --- a/tools/testing/selftests/kvm/demand_paging_test.c
> +++ b/tools/testing/selftests/kvm/demand_paging_test.c
> @@ -32,6 +32,12 @@
>  
>  #define DEFAULT_GUEST_TEST_MEM_SIZE (1 << 30) /* 1G */
>  
> +#ifdef PRINT_PER_PAGE_UPDATES
> +#define PER_PAGE_DEBUG(...) DEBUG(__VA_ARGS__)
> +#else
> +#define PER_PAGE_DEBUG(...)
> +#endif
> +
>  #ifdef PRINT_PER_VCPU_UPDATES
>  #define PER_VCPU_DEBUG(...) DEBUG(__VA_ARGS__)
>  #else
> @@ -64,6 +70,26 @@ static uint64_t guest_test_phys_mem;
>   */
>  static uint64_t guest_test_virt_mem = DEFAULT_GUEST_TEST_MEM;
>  
> +int64_t to_ns(struct timespec ts)
> +{
> +	return (int64_t)ts.tv_nsec + 1000000000LL * (int64_t)ts.tv_sec;
> +}
> +
> +struct timespec diff(struct timespec start, struct  timespec end)
> +{
> +	struct   timespec temp;
> +
> +	if ((end.tv_nsec-start.tv_nsec) < 0) {

spaces around the '-' would be nice

> +		temp.tv_sec = end.tv_sec - start.tv_sec - 1;
> +		temp.tv_nsec = 1000000000 + end.tv_nsec - start.tv_nsec;
> +	} else {
> +		temp.tv_sec = end.tv_sec - start.tv_sec;
> +		temp.tv_nsec = end.tv_nsec - start.tv_nsec;
> +	}
> +
> +	return temp;
> +}

Could probably add these new time utilities to the new test_util.c

Thanks,
drew