[PATCH 2/2] drm/amdgpu: fix fence calculation

[Christian König]

Am 12.05.21 um 21:45 schrieb David M Nieto:
> The proper metric for fence utilization over several
> contexts is an harmonic mean, but such calculation is
> prohibitive in kernel space, so the code approximates it.
>
> Because the approximation diverges when one context has a
> very small ratio compared with the other context, this change
> filter out ratios smaller that 0.01%
>
> Signed-off-by: David M Nieto <david.nieto at amd.com>
> Change-Id: I5b6e0ce5f489a5f55855d35354a6a3653e9d613b

Looks good to me now, but the automated tools complain about "DOS line 
endings" plus a couple of other nit picks and won't let me push it :)

Please use the checkpatch.pl script found in the Linux kernel to fix 
those errors and resend.

Thanks,
Christian.

> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c | 17 +++++++++++++++--
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h |  1 +
>   2 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> index 9036c93b4a0c..b919615e6644 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> @@ -652,12 +652,14 @@ void amdgpu_ctx_mgr_fini(struct amdgpu_ctx_mgr *mgr)
>   	mutex_destroy(&mgr->lock);
>   }
>   
> -void amdgpu_ctx_fence_time(struct amdgpu_ctx *ctx, struct amdgpu_ctx_entity *centity,
> +static void amdgpu_ctx_fence_time(struct amdgpu_ctx *ctx, struct amdgpu_ctx_entity *centity,
>   		ktime_t *total, ktime_t *max)
>   {
>   	ktime_t now, t1;
>   	uint32_t i;
>   
> +	*total = *max = 0;
> +
>   	now = ktime_get();
>   	for (i = 0; i < amdgpu_sched_jobs; i++) {
>   		struct dma_fence *fence;
> @@ -703,11 +705,22 @@ ktime_t amdgpu_ctx_mgr_fence_usage(struct amdgpu_ctx_mgr *mgr, uint32_t hwip,
>   	idp = &mgr->ctx_handles;
>   	mutex_lock(&mgr->lock);
>   	idr_for_each_entry(idp, ctx, id) {
> +		ktime_t ttotal, tmax;
> +
>   		if (!ctx->entities[hwip][idx])
>   			continue;
>   
>   		centity = ctx->entities[hwip][idx];
> -		amdgpu_ctx_fence_time(ctx, centity, &total, &max);
> +		amdgpu_ctx_fence_time(ctx, centity, &ttotal, &tmax);
> +
> +		/* Harmonic mean approximation diverges for very small
> +		 * values. If ratio < 0.01% ignore
> +		 */
> +		if (AMDGPU_CTX_FENCE_USAGE_MIN_RATIO(tmax, ttotal))
> +			continue;
> +
> +		total = ktime_add(total, ttotal);
> +		max = ktime_after(tmax, max) ? tmax : max;
>   	}
>   
>   	mutex_unlock(&mgr->lock);
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h
> index 10dcf59a5c6b..3541dfb059ec 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h
> @@ -30,6 +30,7 @@ struct drm_file;
>   struct amdgpu_fpriv;
>   
>   #define AMDGPU_MAX_ENTITY_NUM 4
> +#define AMDGPU_CTX_FENCE_USAGE_MIN_RATIO(max, total) (max > 16384ULL*total)
>   
>   struct amdgpu_ctx_entity {
>   	uint64_t		sequence;