Re: [PATCH 2/2] drm/amdgpu: use ktime rather than jiffies for benchmark results

[Felix Kuehling]

Am 2022-02-21 um 17:30 schrieb Alex Deucher:
To protect against wraparounds.

Signed-off-by: Alex Deucher <alexander.deuc...@amd.com>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_benchmark.c | 31 ++++++++++---------
  1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_benchmark.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_benchmark.c
index 92a2ffefe62e..3136a9ad2d54 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_benchmark.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_benchmark.c
@@ -29,14 +29,13 @@
  #define AMDGPU_BENCHMARK_COMMON_MODES_N 17
  
  static int amdgpu_benchmark_do_move(struct amdgpu_device *adev, unsigned size,
-                                   uint64_t saddr, uint64_t daddr, int n)
+                                   uint64_t saddr, uint64_t daddr, int n, s64 
*time_ms)
  {
-       unsigned long start_jiffies;
-       unsigned long end_jiffies;
+       ktime_t stime, etime;
        struct dma_fence *fence;
        int i, r;
  
-	start_jiffies = jiffies;
+       stime = ktime_get();
        for (i = 0; i < n; i++) {
                struct amdgpu_ring *ring = adev->mman.buffer_funcs_ring;
                r = amdgpu_copy_buffer(ring, saddr, daddr, size, NULL, &fence,
@@ -48,25 +47,28 @@ static int amdgpu_benchmark_do_move(struct amdgpu_device 
*adev, unsigned size,
                if (r)
                        goto exit_do_move;
        }
-       end_jiffies = jiffies;
-       r = jiffies_to_msecs(end_jiffies - start_jiffies);
  
  exit_do_move:
+       etime = ktime_get();
+       *time_ms = ktime_ms_delta(etime, stime);

Milliseconds are pretty coarse. Would it make sense to use microseconds 
(ktime_us_delta) to get more accurate measurements instead?

Regards,
  Felix


+
        return r;
  }
  
  
  static void amdgpu_benchmark_log_results(struct amdgpu_device *adev,
                                         int n, unsigned size,
-                                        unsigned int time,
+                                        s64 time_ms,
                                         unsigned sdomain, unsigned ddomain,
                                         char *kind)
  {
-       unsigned int throughput = (n * (size >> 10)) / time;
+       s64 throughput = (n * (size >> 10));
+
+       throughput = div64_s64(throughput, time_ms);
  
  	dev_info(adev->dev, "amdgpu: %s %u bo moves of %u kB from"
-                " %d to %d in %u ms, throughput: %u Mb/s or %u MB/s\n",
-                kind, n, size >> 10, sdomain, ddomain, time,
+                " %d to %d in %lld ms, throughput: %lld Mb/s or %lld MB/s\n",
+                kind, n, size >> 10, sdomain, ddomain, time_ms,
                 throughput * 8, throughput);
  }
  
@@ -76,6 +78,7 @@ static int amdgpu_benchmark_move(struct amdgpu_device *adev, unsigned size,
        struct amdgpu_bo *dobj = NULL;
        struct amdgpu_bo *sobj = NULL;
        uint64_t saddr, daddr;
+       s64 time_ms;
        int r, n;
  
  	n = AMDGPU_BENCHMARK_ITERATIONS;
@@ -96,11 +99,11 @@ static int amdgpu_benchmark_move(struct amdgpu_device 
*adev, unsigned size,
                goto out_cleanup;
  
  	if (adev->mman.buffer_funcs) {
-               r = amdgpu_benchmark_do_move(adev, size, saddr, daddr, n);
-               if (r < 0)
+               r = amdgpu_benchmark_do_move(adev, size, saddr, daddr, n, 
&time_ms);
+               if (r)
                        goto out_cleanup;
-               if (r > 0)
-                       amdgpu_benchmark_log_results(adev, n, size, r,
+               else
+                       amdgpu_benchmark_log_results(adev, n, size, time_ms,
                                                     sdomain, ddomain, "dma");
        }