[RFC PATCH v2 08/14] tools/testing/slab: Add object migration test suite

Tobin C. Harding
2019-04-03T04:32:36Z

We just added a module that enables testing the SLUB allocators ability
to defrag/shrink caches via movable objects. Tests are better when they
are automated.

Add automated testing via a python script for SLUB movable objects.

Example output:

$ cd path/to/linux/tools/testing/slab
$ /slub_defrag.py
Please run script as root

$ sudo ./slub_defrag.py
<test are quiet, no output on success>

$ sudo ./slub_defrag.py --debug
Loading module ...
Slab cache smo_test created
Objects per slab: 20
Running sanity checks ...

Running module stress test (see dmesg for additional test output) ...
Removing module slub_defrag ...
Loading module ...
Slab cache smo_test created

Running test non-movable ...
testing slab 'smo_test' prior to enabling movable objects ...
verified non-movable slabs are NOT shrinkable

Running test movable ...
testing slab 'smo_test' after enabling movable objects ...
verified movable slabs are shrinkable

Removing module slub_defrag ...

Signed-off-by: Tobin C. Harding <tobin@kernel.org>
---
tools/testing/slab/slub_defrag.c | 1 +
tools/testing/slab/slub_defrag.py | 451 ++++++++++++++++++++++++++++++
2 files changed, 452 insertions(+)
create mode 100755 tools/testing/slab/slub_defrag.py

diff --git a/tools/testing/slab/slub_defrag.c b/tools/testing/slab/slub_defrag.c
index 4a5c24394b96..8332e69ee868 100644
--- a/tools/testing/slab/slub_defrag.c
+++ b/tools/testing/slab/slub_defrag.c
@@ -337,6 +337,7 @@ static int smo_run_module_tests(int nr_objs, int keep)

/*
* struct functions() - Map command to a function pointer.
+ * If you update this please update the documentation in slub_defrag.py
*/
struct functions {
char *fn_name;
diff --git a/tools/testing/slab/slub_defrag.py b/tools/testing/slab/slub_defrag.py
new file mode 100755
index 000000000000..41747c0db39b
--- /dev/null
+++ b/tools/testing/slab/slub_defrag.py
@@ -0,0 +1,451 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import subprocess
+import sys
+from os import path
+
+# SLUB Movable Objects test suite.
+#
+# Requirements:
+# - CONFIG_SLUB=y
+# - CONFIG_SLUB_DEBUG=y
+# - The slub_defrag module in this directory.
+
+# Test SMO using a kernel module that enables triggering arbitrary
+# kernel code from userspace via a debugfs file.
+#
+# Module code is in ./slub_defrag.c, basically the functionality is as
+# follows:
+#
+# - Creates debugfs file /sys/kernel/debugfs/smo/callfn
+# - Writes to 'callfn' are parsed as a command string and the function
+# associated with command is called.
+# - Defines 4 commands (all commands operate on smo_test cache):
+# - 'test': Runs module stress tests.
+# - 'alloc N': Allocates N slub objects
+# - 'free N POS': Frees N objects starting at POS (see below)
+# - 'enable': Enables SLUB Movable Objects
+#
+# The module maintains a list of allocated objects. Allocation adds
+# objects to the tail of the list. Free'ing frees from the head of the
+# list. This has the effect of creating free slots in the slab. For
+# finer grained control over where in the cache slots are free'd POS
+# (position) argument may be used.
+
+# The main() function is reasonably readable; the test suite does the
+# following:
+#
+# 1. Runs the module stress tests.
+# 2. Tests the cache without movable objects enabled.
+# - Creates multiple partial slabs as explained above.
+# - Verifies that partial slabs are _not_ removed by shrink (see below).
+# 3. Tests the cache with movable objects enabled.
+# - Creates multiple partial slabs as explained above.
+# - Verifies that partial slabs _are_ removed by shrink (see below).
+
+# The sysfs file /sys/kernel/slab/<cache>/shrink enables calling the
+# function kmem_cache_shrink() (see mm/slab_common.c and mm/slub.cc).
+# Shrinking a cache attempts to consolidate all partial slabs by moving
+# objects if object migration is enable for the cache, otherwise
+# shrinking a cache simply re-orders the partial list so as most densely
+# populated slab are at the head of the list.
+
+# Enable/disable debugging output (also enabled via -d | --debug).
+debug = False
+
+# Used in debug messages and when running `insmod`.
+MODULE_NAME = "slub_defrag"
+
+# Slab cache created by the test module.
+CACHE_NAME = "smo_test"
+
+# Set by get_slab_config()
+objects_per_slab = 0
+pages_per_slab = 0
+debugfs_mounted = False # Set to true if we mount debugfs.
+
+
+def eprint(*args, **kwargs):
+ print(*args, file=sys.stderr, **kwargs)
+
+
+def dprint(*args, **kwargs):
+ if debug:
+ print(*args, file=sys.stderr, **kwargs)
+
+
+def run_shell(cmd):
+ return subprocess.call([cmd], shell=True)
+
+
+def run_shell_get_stdout(cmd):
+ return subprocess.check_output([cmd], shell=True)
+
+
+def assert_root():
+ user = run_shell_get_stdout('whoami')
+ if user != b'root\n':
+ eprint("Please run script as root")
+ sys.exit(1)
+
+
+def mount_debugfs():
+ mounted = False
+
+ # Check if debugfs is mounted at a known mount point.
+ ret = run_shell('mount -l | grep /sys/kernel/debug > /dev/null 2>&1')
+ if ret != 0:
+ run_shell('mount -t debugfs none /sys/kernel/debug/')
+ mounted = True
+ dprint("Mounted debugfs on /sys/kernel/debug")
+
+ return mounted
+
+
+def umount_debugfs():
+ dprint("Un-mounting debugfs")
+ run_shell('umount /sys/kernel/debug')
+
+
+def load_module():
+ """Loads the test module.
+
+ We need a clean slab state to start with so module must
+ be loaded by the test suite.
+ """
+ ret = run_shell('lsmod | grep %s > /dev/null' % MODULE_NAME)
+ if ret == 0:
+ eprint("Please unload slub_defrag module before running test suite")
+ return -1
+
+ dprint('Loading module ...')
+ ret = run_shell('insmod %s.ko' % MODULE_NAME)
+ if ret != 0: # ret==1 on error
+ return -1
+
+ dprint("Slab cache %s created" % CACHE_NAME)
+ return 0
+
+
+def unload_module():
+ ret = run_shell('lsmod | grep %s > /dev/null' % MODULE_NAME)
+ if ret == 0:
+ dprint('Removing module %s ...' % MODULE_NAME)
+ run_shell('rmmod %s > /dev/null 2>&1' % MODULE_NAME)
+
+
+def get_sysfs_value(filename):
+ """
+ Parse slab sysfs files (single line: '20 N0=20')
+ """
+ path = '/sys/kernel/slab/smo_test/%s' % filename
+ f = open(path, "r")
+ s = f.readline()
+ tokens = s.split(" ")
+
+ return int(tokens[0])
+
+
+def get_nr_objects_active():
+ return get_sysfs_value('objects')
+
+
+def get_nr_objects_total():
+ return get_sysfs_value('total_objects')
+
+
+def get_nr_slabs_total():
+ return get_sysfs_value('slabs')
+
+
+def get_nr_slabs_partial():
+ return get_sysfs_value('partial')
+
+
+def get_nr_slabs_full():
+ return get_nr_slabs_total() - get_nr_slabs_partial()
+
+
+def get_slab_config():
+ """Get relevant information from sysfs."""
+ global objects_per_slab
+
+ objects_per_slab = get_sysfs_value('objs_per_slab')
+ if objects_per_slab < 0:
+ return -1
+
+ dprint("Objects per slab: %d" % objects_per_slab)
+ return 0
+
+
+def verify_state(nr_objects_active, nr_objects_total,
+ nr_slabs_partial, nr_slabs_full, nr_slabs_total, msg=''):
+ err = 0
+ got_nr_objects_active = get_nr_objects_active()
+ got_nr_objects_total = get_nr_objects_total()
+ got_nr_slabs_partial = get_nr_slabs_partial()
+ got_nr_slabs_full = get_nr_slabs_full()
+ got_nr_slabs_total = get_nr_slabs_total()
+
+ if got_nr_objects_active != nr_objects_active:
+ err = -1
+
+ if got_nr_objects_total != nr_objects_total:
+ err = -2
+
+ if got_nr_slabs_partial != nr_slabs_partial:
+ err = -3
+
+ if got_nr_slabs_full != nr_slabs_full:
+ err = -4
+
+ if got_nr_slabs_total != nr_slabs_total:
+ err = -5
+
+ if err != 0:
+ dprint("Verify state: %s" % msg)
+ dprint(" what\t\t\twant\tgot")
+ dprint("-----------------------------------------")
+ dprint(" %s\t%d\t%d" % ('nr_objects_active', nr_objects_active, got_nr_objects_active))
+ dprint(" %s\t%d\t%d" % ('nr_objects_total', nr_objects_total, got_nr_objects_total))
+ dprint(" %s\t%d\t%d" % ('nr_slabs_partial', nr_slabs_partial, got_nr_slabs_partial))
+ dprint(" %s\t\t%d\t%d" % ('nr_slabs_full', nr_slabs_full, got_nr_slabs_full))
+ dprint(" %s\t%d\t%d\n" % ('nr_slabs_total', nr_slabs_total, got_nr_slabs_total))
+
+ return err
+
+
+def exec_via_sysfs(command):
+ ret = run_shell('echo %s > /sys/kernel/debug/smo/callfn' % command)
+ if ret != 0:
+ eprint("Failed to echo command to sysfs: %s" % command)
+
+ return ret
+
+
+def enable_movable_objects():
+ return exec_via_sysfs('enable')
+
+
+def alloc(n):
+ exec_via_sysfs("alloc %d" % n)
+
+
+def free(n, pos = 0):
+ exec_via_sysfs('free %d %d' % (n, pos))
+
+
+def shrink():
+ ret = run_shell('slabinfo smo_test -s')
+ if ret != 0:
+ eprint("Failed to execute slabinfo -s")
+
+
+def sanity_checks():
+ # Verify everything is 0 to start with.
+ return verify_state(0, 0, 0, 0, 0, "sanity check")
+
+
+def test_non_movable():
+ one_over = objects_per_slab + 1
+
+ dprint("testing slab 'smo_test' prior to enabling movable objects ...")
+
+ alloc(one_over)
+
+ objects_active = one_over
+ objects_total = objects_per_slab * 2
+ slabs_partial = 1
+ slabs_full = 1
+ slabs_total = 2
+ ret = verify_state(objects_active, objects_total,
+ slabs_partial, slabs_full, slabs_total,
+ "non-movable: initial allocation")
+ if ret != 0:
+ eprint("test_non_movable: failed to verify initial state")
+ return -1
+
+ # Free object from first slot of first slab.
+ free(1)
+ objects_active = one_over - 1
+ objects_total = objects_per_slab * 2
+ slabs_partial = 2
+ slabs_full = 0
+ slabs_total = 2
+ ret = verify_state(objects_active, objects_total,
+ slabs_partial, slabs_full, slabs_total,
+ "non-movable: after free")
+ if ret != 0:
+ eprint("test_non_movable: failed to verify after free")
+ return -1
+
+ # Non-movable cache, shrink should have no effect.
+ shrink()
+ ret = verify_state(objects_active, objects_total,
+ slabs_partial, slabs_full, slabs_total,
+ "non-movable: after shrink")
+ if ret != 0:
+ eprint("test_non_movable: failed to verify after shrink")
+ return -1
+
+ # Cleanup
+ free(objects_per_slab)
+ shrink()
+
+ dprint("verified non-movable slabs are NOT shrinkable")
+ return 0
+
+
+def test_movable():
+ one_over = objects_per_slab + 1
+
+ dprint("testing slab 'smo_test' after enabling movable objects ...")
+
+ alloc(one_over)
+
+ objects_active = one_over
+ objects_total = objects_per_slab * 2
+ slabs_partial = 1
+ slabs_full = 1
+ slabs_total = 2
+ ret = verify_state(objects_active, objects_total,
+ slabs_partial, slabs_full, slabs_total,
+ "movable: initial allocation")
+ if ret != 0:
+ eprint("test_movable: failed to verify initial state")
+ return -1
+
+ # Free object from first slot of first slab.
+ free(1)
+ objects_active = one_over - 1
+ objects_total = objects_per_slab * 2
+ slabs_partial = 2
+ slabs_full = 0
+ slabs_total = 2
+ ret = verify_state(objects_active, objects_total,
+ slabs_partial, slabs_full, slabs_total,
+ "movable: after free")
+ if ret != 0:
+ eprint("test_movable: failed to verify after free")
+ return -1
+
+ # movable cache, shrink should move objects and free slab.
+ shrink()
+ objects_active = one_over - 1
+ objects_total = objects_per_slab * 1
+ slabs_partial = 0
+ slabs_full = 1
+ slabs_total = 1
+ ret = verify_state(objects_active, objects_total,
+ slabs_partial, slabs_full, slabs_total,
+ "movable: after shrink")
+ if ret != 0:
+ eprint("test_movable: failed to verify after shrink")
+ return -1
+
+ # Cleanup
+ free(objects_per_slab)
+ shrink()
+
+ dprint("verified movable slabs are shrinkable")
+ return 0
+
+
+def dprint_start_test(test):
+ dprint("Running %s ..." % test)
+
+
+def dprint_done():
+ dprint("")
+
+
+def run_test(fn, desc):
+ dprint_start_test(desc)
+ ret = fn()
+ if ret < 0:
+ fail_test(desc)
+ dprint_done()
+
+
+# Load and unload the module for this test to ensure clean state.
+def run_module_stress_test():
+ dprint("Running module stress test (see dmesg for additional test output) ...")
+
+ unload_module()
+ ret = load_module()
+ if ret < 0:
+ cleanup_and_exit(ret)
+
+ exec_via_sysfs("test");
+
+ unload_module()
+
+ dprint()
+
+
+def fail_test(msg):
+ eprint("\nFAIL: test failed: '%s' ... aborting\n" % msg)
+ cleanup_and_exit(1)
+
+
+def display_help():
+ print("Usage: %s [OPTIONS]\n" % path.basename(sys.argv[0]))
+ print("\tRuns defrag test suite (a.k.a. SLUB Movable Objects)\n")
+ print("OPTIONS:")
+ print("\t-d | --debug Enable verbose debug output")
+ print("\t-h | --help Print this help and exit")
+
+
+def cleanup_and_exit(return_code):
+ global debugfs_mounted
+
+ if debugfs_mounted == True:
+ umount_debugfs()
+
+ unload_module()
+
+ sys.exit(return_code)
+
+
+def main():
+ global debug
+
+ if len(sys.argv) > 1:
+ if sys.argv[1] == '-h' or sys.argv[1] == '--help':
+ display_help()
+ sys.exit(0)
+
+ if sys.argv[1] == '-d' or sys.argv[1] == '--debug':
+ debug = True
+
+ assert_root()
+
+ # Use cleanup_and_exit() instead of sys.exit() after mounting debugfs.
+ debugfs_mounted = mount_debugfs()
+
+ # Loads and unloads the module.
+ run_module_stress_test()
+
+ ret = load_module()
+ if (ret < 0):
+ cleanup_and_exit(ret)
+
+ ret = get_slab_config()
+ if (ret != 0):
+ fail_test("get slab config details")
+
+ run_test(sanity_checks, "sanity checks")
+
+ run_test(test_non_movable, "test non-movable")
+
+ ret = enable_movable_objects()
+ if (ret != 0):
+ fail_test("enable movable objects")
+
+ run_test(test_movable, "test movable")
+
+ cleanup_and_exit(0)
+
+if __name__== "__main__":
+ main()
--
2.21.0