diff --git a/runners/bench_defines.h b/runners/bench_defines.h
index 8f30bc8b..ec455c28 100644
--- a/runners/bench_defines.h
+++ b/runners/bench_defines.h
@@ -32,8 +32,8 @@
     BENCH_DEFINE(GC_PREERASE_COUNT,     -1                                  )
     BENCH_DEFINE(GC_COMPACT_THRESH,     0                                   )
     BENCH_DEFINE(SHRUB_SIZE,            BLOCK_SIZE/4                        )
-    BENCH_DEFINE(FRAGMENT_SIZE,         LFS3_MIN(BLOCK_SIZE/8, 512)         )
-    BENCH_DEFINE(CRYSTAL_THRESH,        BLOCK_SIZE/8                        )
+    BENCH_DEFINE(FRAGMENT_SIZE,         LFS3_MIN(BLOCK_SIZE/16, 512)        )
+    BENCH_DEFINE(CRYSTAL_THRESH,        BLOCK_SIZE/16                       )
     BENCH_DEFINE(LOOKGBMAP_THRESH,      BLOCK_COUNT/4                       )
     // don't bother simulating erases, this may be less realistic, but
     // it's certainly faster!
diff --git a/runners/test_defines.h b/runners/test_defines.h
index 1d8267d5..4ae510b3 100644
--- a/runners/test_defines.h
+++ b/runners/test_defines.h
@@ -23,8 +23,8 @@
     TEST_DEFINE(GC_PREERASE_COUNT,      -1                                  )
     TEST_DEFINE(GC_COMPACT_THRESH,      0                                   )
     TEST_DEFINE(SHRUB_SIZE,             BLOCK_SIZE/4                        )
-    TEST_DEFINE(FRAGMENT_SIZE,          LFS3_MIN(BLOCK_SIZE/8, 512)         )
-    TEST_DEFINE(CRYSTAL_THRESH,         BLOCK_SIZE/8                        )
+    TEST_DEFINE(FRAGMENT_SIZE,          LFS3_MIN(BLOCK_SIZE/16, 512)        )
+    TEST_DEFINE(CRYSTAL_THRESH,         BLOCK_SIZE/16                       )
     TEST_DEFINE(LOOKGBMAP_THRESH,       BLOCK_COUNT/4                       )
     TEST_DEFINE(ERASE_VALUE,            0xff                                )
     #ifndef TEST_KIWIBD