[PATCH-tip v6 20/22] perf bench: Extend mutex/rwlock futex suite to test TP futexes

From: Waiman Long
Date: Wed Mar 22 2017 - 13:43:35 EST

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This patch extends the futex-mutex and futex-rwlock microbenchmarks to
test userspace mutexes and rwlocks built on top of the TP futexes. We
can then compare the relative performance of those userspace locks
based on different type of futexes.

Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
tools/perf/bench/futex-locks.c | 251 +++++++++++++++++++++++++++++++++++++++--
tools/perf/bench/futex.h | 45 ++++++++
tools/perf/check-headers.sh | 4 +
3 files changed, 292 insertions(+), 8 deletions(-)

diff --git a/tools/perf/bench/futex-locks.c b/tools/perf/bench/futex-locks.c
index 88f54c1..bc99be5 100644
--- a/tools/perf/bench/futex-locks.c
+++ b/tools/perf/bench/futex-locks.c
@@ -8,12 +8,14 @@
* indication of actual throughput of the mutex code as it may not really
* need to call into the kernel. Therefore, 3 sets of simple mutex lock and
* unlock functions are written to implenment a mutex lock using the
- * wait-wake (2 versions) and PI futexes respectively. These functions serve
- * as the basis for measuring the locking throughput.
+ * wait-wake, PI, GC and TP futexes respectively. These functions serve as
+ * the basis for measuring the locking throughput.
*
- * Two sets of simple reader/writer lock and unlock functions are also
- * implemented using the wait-wake futexes as well as the Glibc rwlock
- * respectively for performance measurement purpose.
+ * Three sets of simple reader/writer lock and unlock functions are also
+ * implemented using the wait-wake and TP futexes as well as the Glibc
+ * rwlock respectively for performance measurement purpose. The TP futex
+ * writer lock/unlock functions are the same as that of the mutex functions.
+ * That is not the case for the wait-wake futexes.
*/

#include <pthread.h>
@@ -50,6 +52,7 @@ enum {
STAT_OPS, /* # of exclusive locking operations */
STAT_SOPS, /* # of shared locking operations */
STAT_LOCKS, /* # of exclusive lock slowpath count */
+ STAT_KLOCKS, /* # of exclusive kernel locks */
STAT_UNLOCKS, /* # of exclusive unlock slowpath count */
STAT_SLEEPS, /* # of exclusive lock sleeps */
STAT_SLOCKS, /* # of shared lock slowpath count */
@@ -57,6 +60,12 @@ enum {
STAT_SSLEEPS, /* # of shared lock sleeps */
STAT_EAGAINS, /* # of EAGAIN errors */
STAT_WAKEUPS, /* # of wakeups (unlock return) */
+ STAT_HANDOFFS, /* # of lock handoff (TP only) */
+ STAT_STEALS, /* # of lock steals (TP only) */
+ STAT_SLRETRIES, /* # of shared lock retries */
+ STAT_SURETRIES, /* # of shared unlock retries */
+ STAT_SALONES, /* # of shared locking alone ops */
+ STAT_SGROUPS, /* # of shared locking group ops */
STAT_TIMEOUTS, /* # of exclusive lock timeouts */
STAT_LOCKERRS, /* # of exclusive lock errors */
STAT_UNLKERRS, /* # of exclusive unlock errors */
@@ -225,7 +234,7 @@ static inline void stat_inc(int tid __maybe_unused, int item __maybe_unused)
*/
static const struct option mutex_options[] = {
OPT_INTEGER ('d', "locklat", &locklat, "Specify inter-locking latency (default = 1)"),
- OPT_STRING ('f', "ftype", &ftype, "type", "Specify futex type: WW, PI, GC, all (default)"),
+ OPT_STRING ('f', "ftype", &ftype, "type", "Specify futex type: WW, PI, GC, TP, all (default)"),
OPT_INTEGER ('l', "loadlat", &loadlat, "Specify load latency (default = 1)"),
OPT_UINTEGER('r', "runtime", &nsecs, "Specify runtime (in seconds, default = 10s)"),
OPT_BOOLEAN ('S', "shared", &fshared, "Use shared futexes instead of private ones"),
@@ -244,7 +253,7 @@ static inline void stat_inc(int tid __maybe_unused, int item __maybe_unused)

static const struct option rwlock_options[] = {
OPT_INTEGER ('d', "locklat", &locklat, "Specify inter-locking latency (default = 1)"),
- OPT_STRING ('f', "ftype", &ftype, "type", "Specify futex type: WW, GC, all (default)"),
+ OPT_STRING ('f', "ftype", &ftype, "type", "Specify futex type: WW, TP, GC, all (default)"),
OPT_INTEGER ('l', "loadlat", &loadlat, "Specify load latency (default = 1)"),
OPT_UINTEGER('R', "read-%", &rpercent, "Specify reader percentage (default 50%)"),
OPT_UINTEGER('r', "runtime", &nsecs, "Specify runtime (in seconds, default = 10s)"),
@@ -522,6 +531,78 @@ static void gc_mutex_unlock(futex_t *futex __maybe_unused,
pthread_mutex_unlock(&mutex);
}

+/*
+ * TP futex lock/unlock functions
+ */
+static void tp_mutex_lock(futex_t *futex, int tid)
+{
+ futex_t val = 0;
+ int ret;
+ int uscnt = 4; /* Do 4 userspace locks before doing kernel lock */
+
+ if (atomic_cmpxchg_acquire(futex, &val, thread_id))
+ return;
+
+ /*
+ * Retry if an error happens
+ */
+ stat_inc(tid, STAT_LOCKS);
+ for (;;) {
+ FUTEX_CALL(futex_lock, TIME_LOCK, futex, uscnt, ptospec, flags);
+ if (uscnt)
+ uscnt--;
+ else
+ stat_inc(tid, STAT_KLOCKS);
+
+ if (likely(ret >= 0))
+ break;
+ if (errno == EAGAIN) {
+ stat_inc(tid, STAT_EAGAINS);
+ val = 0;
+ if (atomic_cmpxchg_acquire(futex, &val, thread_id))
+ return;
+ continue;
+ }
+ if (errno == ETIMEDOUT) {
+ stat_inc(tid, STAT_TIMEOUTS);
+ } else {
+ stat_inc(tid, STAT_LOCKERRS);
+ }
+ /*
+ * It is possible, though extremely unlikely, that a lock
+ * handoff has happened and an error is returned. So we
+ * need to check for that here.
+ */
+ if ((*futex & FUTEX_SHARED_TID_MASK) == thread_id)
+ return;
+ }
+ /*
+ * Get # of sleeps & locking method
+ */
+ stat_add(tid, STAT_SLEEPS, ret >> 16);
+ ret &= 0xff;
+ if (!ret)
+ stat_inc(tid, STAT_STEALS);
+ else if (ret == 2)
+ stat_inc(tid, STAT_HANDOFFS);
+}
+
+static void tp_mutex_unlock(futex_t *futex, int tid)
+{
+ futex_t val = thread_id;
+ int ret;
+
+ if (atomic_cmpxchg_release(futex, &val, 0))
+ return;
+
+ stat_inc(tid, STAT_UNLOCKS);
+ FUTEX_CALL(futex_unlock, TIME_UNLK, futex, flags);
+ if (ret < 0)
+ stat_inc(tid, STAT_UNLKERRS);
+ else
+ stat_add(tid, STAT_WAKEUPS, ret);
+}
+
/**********************[ RWLOCK lock/unlock functions ]********************/

/*
@@ -814,6 +895,121 @@ static void ww2_read_lock(futex_t *futex __maybe_unused, int tid)
}

/*
+ * TP futex reader/writer lock/unlock functions
+ */
+#define tp_write_lock tp_mutex_lock
+#define tp_write_unlock tp_mutex_unlock
+#define FUTEX_FLAGS_MASK (3UL << 30)
+
+static void tp_read_lock(futex_t *futex, int tid)
+{
+ futex_t val = 0;
+ int ret, retry = 0;
+
+ if (atomic_cmpxchg_acquire(futex, &val, FUTEX_SHARED + 1))
+ return;
+
+ for (;;) {
+ futex_t new;
+
+ /*
+ * Try to increment the reader count only if
+ * 1) the FUTEX_SHARED bit is set; and
+ * 2) none of the flags bits or FUTEX_SHARED_UNLOCK is set.
+ */
+ if (!val)
+ new = FUTEX_SHARED + 1;
+ else if ((val & FUTEX_SHARED) &&
+ !(val & (FUTEX_FLAGS_MASK|FUTEX_SHARED_UNLOCK)))
+ new = val + 1;
+ else
+ break;
+ if (atomic_cmpxchg_acquire(futex, &val, new))
+ goto out;
+ retry++;
+ }
+
+ stat_inc(tid, STAT_SLOCKS);
+ for (;;) {
+ FUTEX_CALL(futex_lock_shared, TIME_SLOCK,
+ futex, !pwriter, ptospec, flags);
+ if (likely(ret >= 0))
+ break;
+ if (errno == ETIMEDOUT)
+ stat_inc(tid, STAT_STIMEOUTS);
+ else
+ stat_inc(tid, STAT_SLOCKERRS);
+ }
+ /*
+ * Get # of sleeps & locking method
+ */
+ stat_add(tid, STAT_SSLEEPS, ret >> 16);
+ if (ret & 0x100)
+ stat_inc(tid, STAT_SALONES); /* In alone mode */
+ if (ret & 0x200)
+ stat_inc(tid, STAT_SGROUPS); /* In group mode */
+
+ ret &= 0xff;
+ if (!ret)
+ stat_inc(tid, STAT_STEALS);
+ else if (ret == 2)
+ stat_inc(tid, STAT_HANDOFFS);
+out:
+ if (unlikely(retry))
+ stat_add(tid, STAT_SLRETRIES, retry);
+}
+
+static void tp_read_unlock(futex_t *futex, int tid)
+{
+ futex_t val;
+ int ret, retry = 0;
+
+ val = atomic_dec_release(futex);
+ if (!(val & FUTEX_SHARED)) {
+ fprintf(stderr,
+ "tp_read_unlock: Incorrect futex value = 0x%x\n", val);
+ exit(1);
+ }
+
+ for (;;) {
+ /*
+ * Return if not the last reader, not in shared locking
+ * mode or the unlock bit has been set.
+ */
+ if ((val & (FUTEX_SCNT_MASK|FUTEX_SHARED_UNLOCK)) ||
+ !(val & FUTEX_SHARED))
+ return;
+
+ if (val & ~FUTEX_SHARED_TID_MASK) {
+ /*
+ * Only one task that can set the FUTEX_SHARED_UNLOCK
+ * bit will do the unlock.
+ */
+ if (atomic_cmpxchg_relaxed(futex, &val,
+ val|FUTEX_SHARED_UNLOCK))
+ break;
+ } else {
+ /*
+ * Try to clear the futex.
+ */
+ if (atomic_cmpxchg_release(futex, &val, 0))
+ goto out;
+ }
+ retry++;
+ }
+
+ stat_inc(tid, STAT_SUNLOCKS);
+ FUTEX_CALL(futex_unlock_shared, TIME_SUNLK, futex, flags);
+ if (ret < 0)
+ stat_inc(tid, STAT_SUNLKERRS);
+ else
+ stat_add(tid, STAT_WAKEUPS, ret);
+out:
+ if (unlikely(retry))
+ stat_add(tid, STAT_SURETRIES, retry);
+}
+
+/*
* Glibc read/write lock
*/
static void gc_write_lock(futex_t *futex __maybe_unused,
@@ -1050,6 +1246,20 @@ static int futex_mutex_type(const char **ptype)
}
pthread_mutex_init(&mutex, attr);
mutex_inited = true;
+ } else if (!strcasecmp(type, "TP")) {
+ *ptype = "TP";
+ mutex_lock_fn = tp_mutex_lock;
+ mutex_unlock_fn = tp_mutex_unlock;
+
+ /*
+ * Check if TP futex is supported.
+ */
+ futex_unlock(&global_futex, 0);
+ if (errno == ENOSYS) {
+ fprintf(stderr,
+ "\nTP futexes are not supported by the kernel!\n");
+ return -1;
+ }
} else {
return -1;
}
@@ -1074,6 +1284,22 @@ static int futex_rwlock_type(const char **ptype)
write_lock_fn = ww_write_lock;
write_unlock_fn = ww_write_unlock;
}
+ } else if (!strcasecmp(type, "TP")) {
+ *ptype = "TP";
+ read_lock_fn = tp_read_lock;
+ read_unlock_fn = tp_read_unlock;
+ write_lock_fn = tp_write_lock;
+ write_unlock_fn = tp_write_unlock;
+
+ /*
+ * Check if TP futex is supported.
+ */
+ futex_unlock(&global_futex, 0);
+ if (errno == ENOSYS) {
+ fprintf(stderr,
+ "\nTP futexes are not supported by the kernel!\n");
+ return -1;
+ }
} else if (!strcasecmp(type, "GC")) {
pthread_rwlockattr_t *attr = NULL;

@@ -1118,6 +1344,7 @@ static void futex_test_driver(const char *futex_type,
[STAT_OPS] = "Total exclusive locking ops",
[STAT_SOPS] = "Total shared locking ops",
[STAT_LOCKS] = "Exclusive lock slowpaths",
+ [STAT_KLOCKS] = "Exclusive kernel locks",
[STAT_UNLOCKS] = "Exclusive unlock slowpaths",
[STAT_SLEEPS] = "Exclusive lock sleeps",
[STAT_SLOCKS] = "Shared lock slowpaths",
@@ -1125,7 +1352,13 @@ static void futex_test_driver(const char *futex_type,
[STAT_SSLEEPS] = "Shared lock sleeps",
[STAT_WAKEUPS] = "Process wakeups",
[STAT_EAGAINS] = "EAGAIN lock errors",
- [STAT_TIMEOUTS] = "Exclusive lock timeouts",
+ [STAT_HANDOFFS] = "Lock handoffs",
+ [STAT_STEALS] = "Lock stealings",
+ [STAT_SLRETRIES] = "Shared lock retries",
+ [STAT_SURETRIES] = "Shared unlock retries",
+ [STAT_SALONES] = "Shared lock ops (alone mode)",
+ [STAT_SGROUPS] = "Shared lock ops (group mode)",
+ [STAT_TIMEOUTS] = "Exclusive lock timeouts",
[STAT_STIMEOUTS] = "Shared lock timeouts",
[STAT_LOCKERRS] = "\nExclusive lock errors",
[STAT_UNLKERRS] = "\nExclusive unlock errors",
@@ -1407,6 +1640,7 @@ int bench_futex_mutex(int argc, const char **argv,
futex_test_driver("WW", futex_mutex_type, mutex_workerfn);
futex_test_driver("PI", futex_mutex_type, mutex_workerfn);
futex_test_driver("GC", futex_mutex_type, mutex_workerfn);
+ futex_test_driver("TP", futex_mutex_type, mutex_workerfn);
} else {
futex_test_driver(ftype, futex_mutex_type, mutex_workerfn);
}
@@ -1433,6 +1667,7 @@ int bench_futex_rwlock(int argc, const char **argv,

if (!ftype || !strcmp(ftype, "all")) {
futex_test_driver("WW", futex_rwlock_type, rwlock_workerfn);
+ futex_test_driver("TP", futex_rwlock_type, rwlock_workerfn);
futex_test_driver("GC", futex_rwlock_type, rwlock_workerfn);
} else {
futex_test_driver(ftype, futex_rwlock_type, rwlock_workerfn);
diff --git a/tools/perf/bench/futex.h b/tools/perf/bench/futex.h
index e44fd32..4ff095e 100644
--- a/tools/perf/bench/futex.h
+++ b/tools/perf/bench/futex.h
@@ -86,6 +86,51 @@
val, opflags);
}

+#ifndef FUTEX_LOCK
+#define FUTEX_LOCK 0xff /* Disable the use of TP futexes */
+#define FUTEX_UNLOCK 0xff
+#define FUTEX_LOCK_SHARED 0xff
+#define FUTEX_UNLOCK_SHARED 0xff
+#endif /* FUTEX_LOCK */
+
+/**
+ * futex_lock() - lock the TP futex
+ */
+static inline int
+futex_lock(u_int32_t *uaddr, bool uslock, struct timespec *timeout, int opflags)
+{
+ return futex(uaddr, FUTEX_LOCK, uslock, timeout, NULL, 0, opflags);
+}
+
+/**
+ * futex_unlock() - unlock the TP futex
+ */
+static inline int
+futex_unlock(u_int32_t *uaddr, int opflags)
+{
+ return futex(uaddr, FUTEX_UNLOCK, 0, NULL, NULL, 0, opflags);
+}
+
+/**
+ * futex_lock_shared() - shared locking of TP futex
+ */
+static inline int
+futex_lock_shared(u_int32_t *uaddr, bool prefer_reader,
+ struct timespec *timeout, int opflags)
+{
+ return futex(uaddr, FUTEX_LOCK_SHARED, prefer_reader, timeout, NULL,
+ 0, opflags);
+}
+
+/**
+ * futex_unlock_shared() - shared unlocking of TP futex
+ */
+static inline int
+futex_unlock_shared(u_int32_t *uaddr, int opflags)
+{
+ return futex(uaddr, FUTEX_UNLOCK_SHARED, 0, NULL, NULL, 0, opflags);
+}
+
#ifndef HAVE_PTHREAD_ATTR_SETAFFINITY_NP
#include <pthread.h>
#include <linux/compiler.h>
diff --git a/tools/perf/check-headers.sh b/tools/perf/check-headers.sh
index c747bfd..6ec5f2d 100755
--- a/tools/perf/check-headers.sh
+++ b/tools/perf/check-headers.sh
@@ -57,3 +57,7 @@ check arch/x86/lib/memcpy_64.S -B -I "^EXPORT_SYMBOL" -I "^#include <asm/
check arch/x86/lib/memset_64.S -B -I "^EXPORT_SYMBOL" -I "^#include <asm/export.h>"
check include/uapi/asm-generic/mman.h -B -I "^#include <\(uapi/\)*asm-generic/mman-common.h>"
check include/uapi/linux/mman.h -B -I "^#include <\(uapi/\)*asm/mman.h>"
+
+# need to link to the latest futex.h header
+[[ -f ../../include/uapi/linux/futex.h ]] &&
+ ln -sf ../../../../../include/uapi/linux/futex.h util/include/linux
--
1.8.3.1

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