iommu/iommu-debug: Use more iterations while profiling

Currently we only take one sample per buffer size per API when doing
profiling.  This results in high run-to-run variance in the results.
Use more iterations to help smooth this out.

Change-Id: I3779007a2f69ef79b573285b2422554f42dda99f
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>

diff --git a/drivers/iommu/iommu-debug.c b/drivers/iommu/iommu-debug.c
index 48e903a..c8081e4 100644 (file)
--- a/drivers/iommu/iommu-debug.c
+++ b/drivers/iommu/iommu-debug.c
@@ -424,6 +424,8 @@ static const char * const _size_to_string(unsigned long size)
        return "unknown size, please add to _size_to_string";
 }
 
+#define ITERS_PER_OP 100
+
 static void iommu_debug_device_profiling(struct seq_file *s, struct device *dev,
                                         bool secure)
 {
@@ -476,33 +478,42 @@ static void iommu_debug_device_profiling(struct seq_file *s, struct device *dev,
                goto out_domain_free;
        }
 
+       seq_printf(s, "(average over %d iterations)\n", ITERS_PER_OP);
        seq_printf(s, "%8s %15s %12s\n", "size", "iommu_map", "iommu_unmap");
        for (sz = sizes; *sz; ++sz) {
                unsigned long size = *sz;
                size_t unmapped;
-               s64 map_elapsed_us, unmap_elapsed_us;
+               u64 map_elapsed_us = 0, unmap_elapsed_us = 0;
                struct timespec tbefore, tafter, diff;
-
-               getnstimeofday(&tbefore);
-               if (iommu_map(domain, iova, paddr, size,
-                             IOMMU_READ | IOMMU_WRITE)) {
-                       seq_puts(s, "Failed to map\n");
-                       continue;
-               }
-               getnstimeofday(&tafter);
-               diff = timespec_sub(tafter, tbefore);
-               map_elapsed_us = div_s64(timespec_to_ns(&diff), 1000);
-
-               getnstimeofday(&tbefore);
-               unmapped = iommu_unmap(domain, iova, size);
-               if (unmapped != size) {
-                       seq_printf(s, "Only unmapped %zx instead of %zx\n",
-                               unmapped, size);
-                       continue;
+               int i;
+
+               for (i = 0; i < ITERS_PER_OP; ++i) {
+                       getnstimeofday(&tbefore);
+                       if (iommu_map(domain, iova, paddr, size,
+                                     IOMMU_READ | IOMMU_WRITE)) {
+                               seq_puts(s, "Failed to map\n");
+                               continue;
+                       }
+                       getnstimeofday(&tafter);
+                       diff = timespec_sub(tafter, tbefore);
+                       map_elapsed_us += div_s64(timespec_to_ns(&diff), 1000);
+
+                       getnstimeofday(&tbefore);
+                       unmapped = iommu_unmap(domain, iova, size);
+                       if (unmapped != size) {
+                               seq_printf(s,
+                                          "Only unmapped %zx instead of %zx\n",
+                                          unmapped, size);
+                               continue;
+                       }
+                       getnstimeofday(&tafter);
+                       diff = timespec_sub(tafter, tbefore);
+                       unmap_elapsed_us += div_s64(timespec_to_ns(&diff),
+                                                   1000);
                }
-               getnstimeofday(&tafter);
-               diff = timespec_sub(tafter, tbefore);
-               unmap_elapsed_us = div_s64(timespec_to_ns(&diff), 1000);
+
+               map_elapsed_us /= ITERS_PER_OP;
+               unmap_elapsed_us /= ITERS_PER_OP;
 
                seq_printf(s, "%8s %12lld us %9lld us\n", _size_to_string(size),
                        map_elapsed_us, unmap_elapsed_us);
@@ -513,10 +524,11 @@ static void iommu_debug_device_profiling(struct seq_file *s, struct device *dev,
        for (sz = sizes; *sz; ++sz) {
                unsigned long size = *sz;
                size_t unmapped;
-               s64 map_elapsed_us, unmap_elapsed_us;
+               u64 map_elapsed_us = 0, unmap_elapsed_us = 0;
                struct timespec tbefore, tafter, diff;
                struct sg_table table;
                unsigned long chunk_size = SZ_4K;
+               int i;
 
                if (iommu_debug_build_phoney_sg_table(dev, &table, size,
                                                      chunk_size)) {
@@ -525,26 +537,33 @@ static void iommu_debug_device_profiling(struct seq_file *s, struct device *dev,
                        goto out_detach;
                }
 
-               getnstimeofday(&tbefore);
-               if (iommu_map_sg(domain, iova, table.sgl, table.nents,
-                                IOMMU_READ | IOMMU_WRITE) != size) {
-                       seq_puts(s, "Failed to map_sg\n");
-                       goto next;
-               }
-               getnstimeofday(&tafter);
-               diff = timespec_sub(tafter, tbefore);
-               map_elapsed_us = div_s64(timespec_to_ns(&diff), 1000);
-
-               getnstimeofday(&tbefore);
-               unmapped = iommu_unmap(domain, iova, size);
-               if (unmapped != size) {
-                       seq_printf(s, "Only unmapped %zx instead of %zx\n",
-                               unmapped, size);
-                       goto next;
+               for (i = 0; i < ITERS_PER_OP; ++i) {
+                       getnstimeofday(&tbefore);
+                       if (iommu_map_sg(domain, iova, table.sgl, table.nents,
+                                        IOMMU_READ | IOMMU_WRITE) != size) {
+                               seq_puts(s, "Failed to map_sg\n");
+                               goto next;
+                       }
+                       getnstimeofday(&tafter);
+                       diff = timespec_sub(tafter, tbefore);
+                       map_elapsed_us += div_s64(timespec_to_ns(&diff), 1000);
+
+                       getnstimeofday(&tbefore);
+                       unmapped = iommu_unmap(domain, iova, size);
+                       if (unmapped != size) {
+                               seq_printf(s,
+                                          "Only unmapped %zx instead of %zx\n",
+                                          unmapped, size);
+                               goto next;
+                       }
+                       getnstimeofday(&tafter);
+                       diff = timespec_sub(tafter, tbefore);
+                       unmap_elapsed_us += div_s64(timespec_to_ns(&diff),
+                                                   1000);
                }
-               getnstimeofday(&tafter);
-               diff = timespec_sub(tafter, tbefore);
-               unmap_elapsed_us = div_s64(timespec_to_ns(&diff), 1000);
+
+               map_elapsed_us /= ITERS_PER_OP;
+               unmap_elapsed_us /= ITERS_PER_OP;
 
                seq_printf(s, "%8s %12lld us %9lld us\n", _size_to_string(size),
                        map_elapsed_us, unmap_elapsed_us);