DTRACE_LOCKSTAT(4) FreeBSD Kernel Interfaces Manual DTRACE_LOCKSTAT(4)
NAME
dtrace_lockstat - a DTrace provider for tracing CPU scheduling events
SYNOPSIS
lockstat:::adaptive-acquire(struct mtx *);
lockstat:::adaptive-release(struct mtx *);
lockstat:::adaptive-spin(struct mtx *, uint64_t);
lockstat:::adaptive-block(struct mtx *, uint64_t);
lockstat:::spin-acquire(struct mtx *);
lockstat:::spin-release(struct mtx *);
lockstat:::spin-spin(struct mtx *, uint64_t);
lockstat:::rw-acquire(struct rwlock *, int);
lockstat:::rw-release(struct rwlock *, int);
lockstat:::rw-block(struct rwlock *, uint64_t, int, int, int);
lockstat:::rw-spin(struct rwlock *, uint64_t);
lockstat:::rw-upgrade(struct rwlock *);
lockstat:::rw-downgrade(struct rwlock *);
lockstat:::sx-acquire(struct sx *, int);
lockstat:::sx-release(struct sx *, int);
lockstat:::sx-block(struct sx *, uint64_t, int, int, int);
lockstat:::sx-spin(struct sx *, uint64_t);
lockstat:::sx-upgrade(struct sx *);
lockstat:::sx-downgrade(struct sx *);
lockstat:::lockmgr-acquire(struct lock *, int);
lockstat:::lockmgr-release(struct lock *, int);
lockstat:::lockmgr-disown(struct lock *, int);
lockstat:::lockmgr-block(struct lock *, uint64_t, int, int, int);
lockstat:::lockmgr-upgrade(struct lock *);
lockstat:::lockmgr-downgrade(struct lock *);
lockstat:::thread-spin(struct mtx *, uint64);
DESCRIPTION
The DTrace lockstat provider allows the tracing of events related to
locking on FreeBSD.
The dtrace_lockstat provider contains DTrace probes for inspecting kernel
lock state transitions. Probes exist for the lockmgr(9), mutex(9),
rwlock(9), and sx(9) lock types. The lockstat(1) utility can be used to
collect and display data collected from the dtrace_lockstat provider.
Each type of lock has acquire() and release() probes which expose the
lock structure being operated upon, as well as probes which fire when a
thread contends with other threads for ownership of a lock.
The lockstat:::adaptive-acquire() and lockstat:::adaptive-release()
probes fire when an MTX_DEF mutex(9) is acquired and released,
respectively. The only argument is a pointer to the lock structure which
describes the lock being acquired or released.
The lockstat:::adaptive-spin() probe fires when a thread spins while
waiting for a MTX_DEF mutex(9) to be released by another thread. The
first argument is a pointer to the lock structure that describes the lock
and the second argument is the amount of time, in nanoseconds, that the
mutex spent spinning. The lockstat:::adaptive-block() probe fires when a
thread takes itself off the CPU while trying to acquire an MTX_DEF
mutex(9) that is owned by another thread. The first argument is a
pointer to the lock structure that describes the lock and the second
argument is the length of time, in nanoseconds, that the waiting thread
was blocked. The lockstat:::adaptive-block() and
lockstat:::adaptive-spin() probes fire only after the lock has been
successfully acquired, and in particular, after the
lockstat:::adaptive-acquire() probe fires.
The lockstat:::spin-acquire() and lockstat:::spin-release() probes fire
when a MTX_SPIN mutex(9) is acquired or released, respectively. The only
argument is a pointer to the lock structure which describes the lock
being acquired or released.
The lockstat:::spin-spin() probe fires when a thread spins while waiting
for a MTX_SPIN mutex(9) to be released by another thread. The first
argument is a pointer to the lock structure that describes the lock and
the second argument is the length of the time spent spinning, in
nanoseconds. The lockstat:::spin-spin() probe fires only after the lock
has been successfully acquired, and in particular, after the
lockstat:::spin-acquire() probe fires.
The lockstat:::rw-acquire() and lockstat:::rw-release() probes fire when
a rwlock(9) is acquired or released, respectively. The first argument is
a pointer to the structure which describes the lock being acquired. The
second argument is 0 if the lock is being acquired or released as a
writer, and 1 if it is being acquired or released as a reader. The
lockstat:::sx-acquire() and lockstat:::sx-release(), and
lockstat:::lockmgr-acquire() and lockstat:::lockmgr-release() probes fire
upon the corresponding events for sx(9) and lockmgr(9) locks,
respectively. The lockstat:::lockmgr-disown() probe fires when a
lockmgr(9) exclusive lock is disowned. In this state, the lock remains
exclusively held, but may be released by a different thread. The
lockstat:::lockmgr-release() probe does not fire when releasing a
disowned lock. The first argument is a pointer to the structure which
describes the lock being disowned. The second argument is 0, for
compatibility with lockstat:::lockmgr-release().
The lockstat:::rw-block(), lockstat:::sx-block(), and
lockstat:::lockmgr-block() probes fire when a thread removes itself from
the CPU while waiting to acquire a lock of the corresponding type. The
lockstat:::rw-spin() and lockstat:::sx-spin() probes fire when a thread
spins while waiting to acquire a lock of the corresponding type. All
probes take the same set of arguments. The first argument is a pointer
to the lock structure that describes the lock. The second argument is
the length of time, in nanoseconds, that the waiting thread was off the
CPU or spinning for the lock. The third argument is 0 if the thread is
attempting to acquire the lock as a writer, and 1 if the thread is
attempting to acquire the lock as a reader. The fourth argument is 0 if
the thread is waiting for a reader to release the lock, and 1 if the
thread is waiting for a writer to release the lock. The fifth argument
is the number of readers that held the lock when the thread first
attempted to acquire the lock. This argument will be 0 if the fourth
argument is 1.
The lockstat:::lockmgr-upgrade(), lockstat:::rw-upgrade(), and
lockstat:::sx-upgrade() probes fire when a thread successfully upgrades a
held lockmgr(9), rwlock(9), or sx(9) shared/reader lock to an
exclusive/writer lock. The only argument is a pointer to the structure
which describes the lock being acquired. The
lockstat:::lockmgr-downgrade(), lockstat:::rw-downgrade(), and
lockstat:::sx-downgrade() probes fire when a thread downgrades a held
lockmgr(9), rwlock(9), or sx(9) exclusive/writer lock to a shared/reader
lock.
The lockstat:::thread-spin() probe fires when a thread spins on a thread
lock, which is a specialized MTX_SPIN mutex(9). The first argument is a
pointer to the structure that describes the lock and the second argument
is the length of time, in nanoseconds, that the thread was spinning.
SEE ALSO
dtrace(1), lockstat(1), locking(9), mutex(9), rwlock(9), SDT(9), sx(9)
HISTORY
The dtrace_lockstat provider first appeared in Solaris. The FreeBSD
implementation of the dtrace_lockstat provider first appeared in
FreeBSD 9.
AUTHORS
This manual page was written by George V. Neville-Neil <gnn@FreeBSD.org>
and Mark Johnston <markj@FreeBSD.org>.
BUGS
Probes for rmlock(9) locks have not yet been added.
FreeBSD 13.1-RELEASE-p6 August 20, 2019 FreeBSD 13.1-RELEASE-p6
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