diff --git a/.travis.yml b/.travis.yml
index d8c9e385bbc..d770e7261f5 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,11 +4,11 @@ before_install:
   - sudo apt-get update -qq
   - sudo apt-get install -qq libgtest-dev libgflags-dev python-virtualenv
 script:
-  - ./tools/run_tests/run_tests.py -l c -t -j 16 -c dbg
-  - ./tools/run_tests/run_tests.py -l c++ -t -j 16 -c dbg
+  - ./tools/run_tests/run_tests.py -l c -t -j 16 -c dbg -s 2.0
+  - ./tools/run_tests/run_tests.py -l c++ -t -j 16 -c dbg -s 2.0
   - make clean
-  - ./tools/run_tests/run_tests.py -l c -t -j 16 -c opt
-  - ./tools/run_tests/run_tests.py -l c++ -t -j 16 -c opt
+  - ./tools/run_tests/run_tests.py -l c -t -j 16 -c opt -s 2.0
+  - ./tools/run_tests/run_tests.py -l c++ -t -j 16 -c opt -s 2.0
   - ./tools/run_tests/run_tests.py -l node -t -j 16 -c opt
 notifications:
   email: false
diff --git a/Makefile b/Makefile
index 2baf0d6ba2a..c850ec77533 100644
--- a/Makefile
+++ b/Makefile
@@ -77,7 +77,7 @@ LDXX_valgrind = g++
 CPPFLAGS_valgrind = -O0
 OPENSSL_CFLAGS_valgrind = -DPURIFY
 LDFLAGS_valgrind =
-DEFINES_valgrind = _DEBUG DEBUG GRPC_TEST_SLOWDOWN_FACTOR=20
+DEFINES_valgrind = _DEBUG DEBUG GRPC_TEST_SLOWDOWN_BUILD_FACTOR=20
 
 VALID_CONFIG_tsan = 1
 REQUIRE_CUSTOM_LIBRARIES_tsan = 1
@@ -87,7 +87,7 @@ LD_tsan = clang
 LDXX_tsan = clang++
 CPPFLAGS_tsan = -O1 -fsanitize=thread -fno-omit-frame-pointer
 LDFLAGS_tsan = -fsanitize=thread
-DEFINES_tsan = NDEBUG GRPC_TEST_SLOWDOWN_FACTOR=10
+DEFINES_tsan = NDEBUG GRPC_TEST_SLOWDOWN_BUILD_FACTOR=10
 
 VALID_CONFIG_asan = 1
 REQUIRE_CUSTOM_LIBRARIES_asan = 1
@@ -97,7 +97,7 @@ LD_asan = clang
 LDXX_asan = clang++
 CPPFLAGS_asan = -O1 -fsanitize=address -fno-omit-frame-pointer
 LDFLAGS_asan = -fsanitize=address
-DEFINES_asan = NDEBUG GRPC_TEST_SLOWDOWN_FACTOR=5
+DEFINES_asan = NDEBUG GRPC_TEST_SLOWDOWN_BUILD_FACTOR=5
 
 VALID_CONFIG_msan = 1
 REQUIRE_CUSTOM_LIBRARIES_msan = 1
@@ -108,7 +108,7 @@ LDXX_msan = clang++-libc++
 CPPFLAGS_msan = -O1 -fsanitize=memory -fsanitize-memory-track-origins -fno-omit-frame-pointer -DGTEST_HAS_TR1_TUPLE=0 -DGTEST_USE_OWN_TR1_TUPLE=1
 OPENSSL_CFLAGS_msan = -DPURIFY
 LDFLAGS_msan = -fsanitize=memory -DGTEST_HAS_TR1_TUPLE=0 -DGTEST_USE_OWN_TR1_TUPLE=1
-DEFINES_msan = NDEBUG GRPC_TEST_SLOWDOWN_FACTOR=20
+DEFINES_msan = NDEBUG GRPC_TEST_SLOWDOWN_BUILD_FACTOR=20
 
 VALID_CONFIG_ubsan = 1
 REQUIRE_CUSTOM_LIBRARIES_ubsan = 1
@@ -119,7 +119,7 @@ LDXX_ubsan = clang++
 CPPFLAGS_ubsan = -O1 -fsanitize=undefined -fno-omit-frame-pointer
 OPENSSL_CFLAGS_ubsan = -DPURIFY
 LDFLAGS_ubsan = -fsanitize=undefined
-DEFINES_ubsan = NDEBUG GRPC_TEST_SLOWDOWN_FACTOR=10
+DEFINES_ubsan = NDEBUG GRPC_TEST_SLOWDOWN_BUILD_FACTOR=10
 
 VALID_CONFIG_gcov = 1
 CC_gcov = gcc
@@ -178,6 +178,10 @@ CPPFLAGS += $(CPPFLAGS_$(CONFIG))
 DEFINES += $(DEFINES_$(CONFIG)) INSTALL_PREFIX=\"$(prefix)\"
 LDFLAGS += $(LDFLAGS_$(CONFIG))
 
+ifdef EXTRA_DEFINES
+DEFINES += $(EXTRA_DEFINES)
+endif
+
 CFLAGS += -std=c89 -pedantic
 ifeq ($(HAS_CXX11),true)
 CXXFLAGS += -std=c++11
diff --git a/templates/Makefile.template b/templates/Makefile.template
index 491f142142e..0413f19e44e 100644
--- a/templates/Makefile.template
+++ b/templates/Makefile.template
@@ -94,7 +94,7 @@ LDXX_valgrind = g++
 CPPFLAGS_valgrind = -O0
 OPENSSL_CFLAGS_valgrind = -DPURIFY
 LDFLAGS_valgrind =
-DEFINES_valgrind = _DEBUG DEBUG GRPC_TEST_SLOWDOWN_FACTOR=20
+DEFINES_valgrind = _DEBUG DEBUG GRPC_TEST_SLOWDOWN_BUILD_FACTOR=20
 
 VALID_CONFIG_tsan = 1
 REQUIRE_CUSTOM_LIBRARIES_tsan = 1
@@ -104,7 +104,7 @@ LD_tsan = clang
 LDXX_tsan = clang++
 CPPFLAGS_tsan = -O1 -fsanitize=thread -fno-omit-frame-pointer
 LDFLAGS_tsan = -fsanitize=thread
-DEFINES_tsan = NDEBUG GRPC_TEST_SLOWDOWN_FACTOR=10
+DEFINES_tsan = NDEBUG GRPC_TEST_SLOWDOWN_BUILD_FACTOR=10
 
 VALID_CONFIG_asan = 1
 REQUIRE_CUSTOM_LIBRARIES_asan = 1
@@ -114,7 +114,7 @@ LD_asan = clang
 LDXX_asan = clang++
 CPPFLAGS_asan = -O1 -fsanitize=address -fno-omit-frame-pointer
 LDFLAGS_asan = -fsanitize=address
-DEFINES_asan = NDEBUG GRPC_TEST_SLOWDOWN_FACTOR=5
+DEFINES_asan = NDEBUG GRPC_TEST_SLOWDOWN_BUILD_FACTOR=5
 
 VALID_CONFIG_msan = 1
 REQUIRE_CUSTOM_LIBRARIES_msan = 1
@@ -125,7 +125,7 @@ LDXX_msan = clang++-libc++
 CPPFLAGS_msan = -O1 -fsanitize=memory -fsanitize-memory-track-origins -fno-omit-frame-pointer -DGTEST_HAS_TR1_TUPLE=0 -DGTEST_USE_OWN_TR1_TUPLE=1
 OPENSSL_CFLAGS_msan = -DPURIFY
 LDFLAGS_msan = -fsanitize=memory -DGTEST_HAS_TR1_TUPLE=0 -DGTEST_USE_OWN_TR1_TUPLE=1
-DEFINES_msan = NDEBUG GRPC_TEST_SLOWDOWN_FACTOR=20
+DEFINES_msan = NDEBUG GRPC_TEST_SLOWDOWN_BUILD_FACTOR=20
 
 VALID_CONFIG_ubsan = 1
 REQUIRE_CUSTOM_LIBRARIES_ubsan = 1
@@ -136,7 +136,7 @@ LDXX_ubsan = clang++
 CPPFLAGS_ubsan = -O1 -fsanitize=undefined -fno-omit-frame-pointer
 OPENSSL_CFLAGS_ubsan = -DPURIFY
 LDFLAGS_ubsan = -fsanitize=undefined
-DEFINES_ubsan = NDEBUG GRPC_TEST_SLOWDOWN_FACTOR=10
+DEFINES_ubsan = NDEBUG GRPC_TEST_SLOWDOWN_BUILD_FACTOR=10
 
 VALID_CONFIG_gcov = 1
 CC_gcov = gcc
@@ -195,6 +195,10 @@ CPPFLAGS += $(CPPFLAGS_$(CONFIG))
 DEFINES += $(DEFINES_$(CONFIG)) INSTALL_PREFIX=\"$(prefix)\"
 LDFLAGS += $(LDFLAGS_$(CONFIG))
 
+ifdef EXTRA_DEFINES
+DEFINES += EXTRA_DEFINES
+endif
+
 CFLAGS += -std=c89 -pedantic
 ifeq ($(HAS_CXX11),true)
 CXXFLAGS += -std=c++11
diff --git a/test/build/c++11.cc b/test/build/c++11.cc
index 519395f20a4..4822a20e7f2 100644
--- a/test/build/c++11.cc
+++ b/test/build/c++11.cc
@@ -31,7 +31,7 @@
  *
  */
 
-/* This is just a compilation test, to see if we have zlib installed. */
+/* This is just a compilation test, to see if we have C++11. */
 
 #include <stdlib.h>
 #include <zlib.h>
diff --git a/test/core/util/port_posix.c b/test/core/util/port_posix.c
index 55150a7cedc..36f13e1b51e 100644
--- a/test/core/util/port_posix.c
+++ b/test/core/util/port_posix.c
@@ -117,9 +117,10 @@ int grpc_pick_unused_port(void) {
 
   for (;;) {
     int port;
-    if (try == 0) {
+    try++;
+    if (try == 1) {
       port = getpid() % (65536 - 30000) + 30000;
-    } else if (try < NUM_RANDOM_PORTS_TO_PICK) {
+    } else if (try <= NUM_RANDOM_PORTS_TO_PICK) {
       port = rand() % (65536 - 30000) + 30000;
     } else {
       port = 0;
diff --git a/test/core/util/test_config.c b/test/core/util/test_config.c
index 1c464073114..1f0f0175b1c 100644
--- a/test/core/util/test_config.c
+++ b/test/core/util/test_config.c
@@ -34,6 +34,7 @@
 #include "test/core/util/test_config.h"
 
 #include <grpc/support/port_platform.h>
+#include <grpc/support/log.h>
 #include <stdlib.h>
 #include <signal.h>
 
@@ -52,6 +53,9 @@ void grpc_test_init(int argc, char **argv) {
   /* disable SIGPIPE */
   signal(SIGPIPE, SIG_IGN);
 #endif
+  gpr_log(GPR_DEBUG, "test slowdown: machine=%f build=%f total=%f",
+          GRPC_TEST_SLOWDOWN_MACHINE_FACTOR, GRPC_TEST_SLOWDOWN_BUILD_FACTOR,
+          GRPC_TEST_SLOWDOWN_FACTOR);
   /* seed rng with pid, so we don't end up with the same random numbers as a
      concurrently running test binary */
   srand(seed());
diff --git a/test/core/util/test_config.h b/test/core/util/test_config.h
index 74c2a3cf1b1..5292c7b525e 100644
--- a/test/core/util/test_config.h
+++ b/test/core/util/test_config.h
@@ -40,16 +40,23 @@
 extern "C" {
 #endif /*  __cplusplus */
 
-#ifndef GRPC_TEST_SLOWDOWN_FACTOR
-#define GRPC_TEST_SLOWDOWN_FACTOR 1.0
+#ifndef GRPC_TEST_SLOWDOWN_BUILD_FACTOR
+#define GRPC_TEST_SLOWDOWN_BUILD_FACTOR 1.0
 #endif
 
+#ifndef GRPC_TEST_SLOWDOWN_MACHINE_FACTOR
+#define GRPC_TEST_SLOWDOWN_MACHINE_FACTOR 1.0
+#endif
+
+#define GRPC_TEST_SLOWDOWN_FACTOR \
+  (GRPC_TEST_SLOWDOWN_BUILD_FACTOR * GRPC_TEST_SLOWDOWN_MACHINE_FACTOR)
+
 #define GRPC_TIMEOUT_SECONDS_TO_DEADLINE(x) \
   gpr_time_add(gpr_now(),                   \
                gpr_time_from_micros(GRPC_TEST_SLOWDOWN_FACTOR * 1e6 * (x)))
 
 #define GRPC_TIMEOUT_MILLIS_TO_DEADLINE(x) \
-  gpr_time_add(gpr_now(),                   \
+  gpr_time_add(gpr_now(),                  \
                gpr_time_from_micros(GRPC_TEST_SLOWDOWN_FACTOR * 1e3 * (x)))
 
 void grpc_test_init(int argc, char **argv);
diff --git a/tools/run_tests/jobset.py b/tools/run_tests/jobset.py
index b8178ffebf1..ad65da535b4 100755
--- a/tools/run_tests/jobset.py
+++ b/tools/run_tests/jobset.py
@@ -99,6 +99,7 @@ _CLEAR_LINE = '\x1b[2K'
 
 _TAG_COLOR = {
     'FAILED': 'red',
+    'TIMEOUT': 'red',
     'PASSED': 'green',
     'START': 'gray',
     'WAITING': 'yellow',
diff --git a/tools/run_tests/run_tests.py b/tools/run_tests/run_tests.py
index 22f12b019a6..4e0ff85c59d 100755
--- a/tools/run_tests/run_tests.py
+++ b/tools/run_tests/run_tests.py
@@ -171,6 +171,7 @@ argp.add_argument('-c', '--config',
 argp.add_argument('-n', '--runs_per_test', default=1, type=int)
 argp.add_argument('-r', '--regex', default='.*', type=str)
 argp.add_argument('-j', '--jobs', default=1000, type=int)
+argp.add_argument('-s', '--slowdown', default=1.0, type=float)
 argp.add_argument('-f', '--forever',
                   default=False,
                   action='store_const',
@@ -200,6 +201,7 @@ make_targets = []
 languages = set(_LANGUAGES[l] for l in args.language)
 build_steps = [jobset.JobSpec(['make',
                                '-j', '%d' % (multiprocessing.cpu_count() + 1),
+                               'EXTRA_DEFINES=GRPC_TEST_SLOWDOWN_MACHINE_FACTOR=%f' % args.slowdown,
                                'CONFIG=%s' % cfg] + list(set(
                                    itertools.chain.from_iterable(
                                        l.make_targets() for l in languages))))