diff --git a/example/mu-impl-fast.yml b/example/mu-impl-fast.yml
index 68fcca83a40b513bb22b6b76090b12c93a729b03..2ed7d1f75a6f37193707b0181e7824fd28fb90c7 100644
--- a/example/mu-impl-fast.yml
+++ b/example/mu-impl-fast.yml
@@ -12,60 +12,60 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-fib:
-  iterations: 20
-  benchmark:
-    name: micro/fib
-    args:
-      - 10  # scale factor
-      - 35
-  callback:
-    name: clock
-    param: "6"
-  tasks:
-    rpyc_O3:
-      language:
-        name: rpython
-        backend: c
-      source: targetfib.py
-      compiler:
-        flags:
-          - --gc=none
-      environ:
-        PYPY_C_CLANG_OPT_FLAG: -O3
-        PYPY_USESSION_BASENAME: fib_rpyc_O3
-    rpyzebu:
-      language:
-        name: rpython
-        backend: mu
-        impl: zebu
-      source: targetfib.py
-      compiler:
-        pypydir: $PYPY_MU
-      environ:
-        ZEBU_BUILD: release
-        PYPY_USESSION_DIR: example
-        PYPY_USESSION_BASENAME: fib_rpyzebu
-    c_O3:
-      language: c
-      source: fib.c
-      compiler:
-        flags:
-          - -O3
-    mu_fast:
-      language:
-        name: mu
-        impl: zebu
-      source: build_fib.c
-      compiler:
-        flags:
-          - -DBUILD_FIB_FAST
+# fib:
+#   iterations: 20
+#   benchmark:
+#     name: micro/fib
+#     args:
+#       - 10  # scale factor
+#       - 35
+#   callback:
+#     name: clock
+#     param: "6"
+#   tasks:
+#     rpyc_O3:
+#       language:
+#         name: rpython
+#         backend: c
+#       source: targetfib.py
+#       compiler:
+#         flags:
+#           - --gc=none
+#       environ:
+#         PYPY_C_CLANG_OPT_FLAG: -O3
+#         PYPY_USESSION_BASENAME: fib_rpyc_O3
+#     rpyzebu:
+#       language:
+#         name: rpython
+#         backend: mu
+#         impl: zebu
+#       source: targetfib.py
+#       compiler:
+#         pypydir: $PYPY_MU
+#       environ:
+#         ZEBU_BUILD: release
+#         PYPY_USESSION_DIR: example
+#         PYPY_USESSION_BASENAME: fib_rpyzebu
+#     c_O3:
+#       language: c
+#       source: fib.c
+#       compiler:
+#         flags:
+#           - -O3
+#     mu_fast:
+#       language:
+#         name: mu
+#         impl: zebu
+#       source: build_fib.c
+#       compiler:
+#         flags:
+#           - -DBUILD_FIB_FAST
 alloc:
   iterations: 20
   benchmark:
     name: micro/alloc
     args:
-      - 10  # scale factor
+      - 2000  # scale factor
       - 10000
   callback:
     name: clock
@@ -76,118 +76,125 @@ alloc:
         name: rpython
         backend: c
       source: targetalloc.py
-    rpyzebu:
-      language:
-        name: rpython
-        backend: mu
-        impl: zebu
-      source: targetalloc.py
-except:
-  benchmark:
-    name: micro/except
-    args:
-      - 2000
-      - 1
-      - 10
-  iterations: 20
-  callback:
-    name: clock
-    param: "6"
-  environ:
-    PYPY_USESSION_DIR: example
-  tasks:
-    rpyc_O3:
-      language:
-        name: rpython
-        backend: c
-      source: targetexcept.py
-      environ:
-        PYPY_C_CLANG_OPT_FLAG: -O3
-        PYPY_USESSION_BASENAME: "${MUBENCH_TASKSET_NAME}_${MUBENCH_TASK_NAME}"
-    rpyzebu:
-      language:
-        name: rpython
-        backend: mu
-        impl: zebu
-      source: targetexcept.py
-      environ:
-        PYPY_USESSION_BASENAME: except_rpyzebu
-som:
-  iterations: 20
-  benchmark:
-    name: SOM
-    args:
-      - -cp
-      - $RPYSOM/Smalltalk
-      - $RPYSOM/TestSuite/TestHarness.som
-  callback:
-    name: clock
-    param: "6"
-  environ:
-    PYPY_USESSION_DIR: example  # controls where PyPy puts usession directory
-    PYTHONPATH: $RPYSOM/src
-  tasks:
-    rpyc_O3:
-      language:
-        name: rpython
-        backend: c
-      source: targetrpysom.py
-      environ:
-        PYPY_C_CLANG_OPT_FLAG: -O3
-        PYPY_USESSION_BASENAME: som_rpyc_O3
-    rpyzebu:
-      language:
-        name: rpython
-        backend: mu
-        impl: zebu
-      source: targetrpysom.py
-      environ:
-        ZEBU_BUILD: "release"
-        PYPY_USESSION_BASENAME: som_rpyzebu
-quicksort:
-  benchmark:
-    name: micro/quicksort
-  iterations: 20
-  callback:
-    name: clock
-    param: "6"
-  environ:
-    PYPY_USESSION_DIR: example
-  tasks:
-    rpyc_O0:
-      language:
-        name: rpython
-        backend: c
-      source: targetquicksort.py
-      environ:
-        PYPY_C_CLANG_OPT_FLAG: -O0
-        PYPY_USESSION_BASENAME: &basename "${MUBENCH_TASKSET_NAME}_${MUBENCH_TASK_NAME}"
-      flags:
-        - --gc=none
       compiler:
-        args:
-          - &scale_factor 1000
-    rpyc_O3:
-      language:
-        name: rpython
-        backend: c
-      source: targetquicksort.py
-      environ:
-        PYPY_C_CLANG_OPT_FLAG: -O3
-        PYPY_USESSION_BASENAME: *basename
-      flags:
-        - --gc=none
-      compiler:
-        args:
-          - *scale_factor
+        flags:
+          - --gc=none   # disable GC on PyPy
     rpyzebu:
       language:
         name: rpython
         backend: mu
         impl: zebu
-      source: targetquicksort.py
-      environ:
-        PYPY_USESSION_BASENAME: *basename
+      source: targetalloc.py
       compiler:
-        args:
-          - *scale_factor
+        vmargs:
+          - --gc-immixspace-size=524288000  # 500M
+          - --gc-lospace-size=104587600     # 100M
+# except:
+#   benchmark:
+#     name: micro/except
+#     args:
+#       - 2000
+#       - 1
+#       - 10
+#   iterations: 20
+#   callback:
+#     name: clock
+#     param: "6"
+#   environ:
+#     PYPY_USESSION_DIR: example
+#   tasks:
+#     rpyc_O3:
+#       language:
+#         name: rpython
+#         backend: c
+#       source: targetexcept.py
+#       environ:
+#         PYPY_C_CLANG_OPT_FLAG: -O3
+#         PYPY_USESSION_BASENAME: "${MUBENCH_TASKSET_NAME}_${MUBENCH_TASK_NAME}"
+#     rpyzebu:
+#       language:
+#         name: rpython
+#         backend: mu
+#         impl: zebu
+#       source: targetexcept.py
+#       environ:
+#         PYPY_USESSION_BASENAME: except_rpyzebu
+# som:
+#   iterations: 20
+#   benchmark:
+#     name: SOM
+#     args:
+#       - -cp
+#       - $RPYSOM/Smalltalk
+#       - $RPYSOM/TestSuite/TestHarness.som
+#   callback:
+#     name: clock
+#     param: "6"
+#   environ:
+#     PYPY_USESSION_DIR: example  # controls where PyPy puts usession directory
+#     PYTHONPATH: $RPYSOM/src
+#   tasks:
+#     rpyc_O3:
+#       language:
+#         name: rpython
+#         backend: c
+#       source: targetrpysom.py
+#       environ:
+#         PYPY_C_CLANG_OPT_FLAG: -O3
+#         PYPY_USESSION_BASENAME: som_rpyc_O3
+#     rpyzebu:
+#       language:
+#         name: rpython
+#         backend: mu
+#         impl: zebu
+#       source: targetrpysom.py
+#       environ:
+#         ZEBU_BUILD: "release"
+#         PYPY_USESSION_BASENAME: som_rpyzebu
+# quicksort:
+#   benchmark:
+#     name: micro/quicksort
+#   iterations: 20
+#   callback:
+#     name: clock
+#     param: "6"
+#   environ:
+#     PYPY_USESSION_DIR: example
+#   tasks:
+#     rpyc_O0:
+#       language:
+#         name: rpython
+#         backend: c
+#       source: targetquicksort.py
+#       environ:
+#         PYPY_C_CLANG_OPT_FLAG: -O0
+#         PYPY_USESSION_BASENAME: &basename "${MUBENCH_TASKSET_NAME}_${MUBENCH_TASK_NAME}"
+#       flags:
+#         - --gc=none
+#       compiler:
+#         args:
+#           - &scale_factor 1000
+#     rpyc_O3:
+#       language:
+#         name: rpython
+#         backend: c
+#       source: targetquicksort.py
+#       environ:
+#         PYPY_C_CLANG_OPT_FLAG: -O3
+#         PYPY_USESSION_BASENAME: *basename
+#       flags:
+#         - --gc=none
+#       compiler:
+#         args:
+#           - *scale_factor
+#     rpyzebu:
+#       language:
+#         name: rpython
+#         backend: mu
+#         impl: zebu
+#       source: targetquicksort.py
+#       environ:
+#         PYPY_USESSION_BASENAME: *basename
+#       compiler:
+#         args:
+#           - *scale_factor
diff --git a/mubench/suite/micro/alloc/targetalloc.py b/mubench/suite/micro/alloc/targetalloc.py
index 6d08f132a69c4fac0115d8f7f13e3890496bd237..34a6be7175191d1a1ebb4a425a133add92b5af40 100644
--- a/mubench/suite/micro/alloc/targetalloc.py
+++ b/mubench/suite/micro/alloc/targetalloc.py
@@ -30,14 +30,16 @@ def target(driver, args):
         scale_factor = int(argv[2])
         n = int(argv[3])
 
-        lst = []
+        lst = [[None] * n] * scale_factor
 
         cb.begin()
         for j in range(scale_factor):
+            l = lst[j]
             for k in range(n):
-                lst.append(A())
+                l[k] = A()
         cb.end()
         cb.report()
-        return int(not (len(lst) == n * scale_factor))
+        # return int(not (len(lst) == n * scale_factor))
+        return 0
 
     return main, None