On Tue, Jan 22, 2019 at 10:49:09PM -0500, Waiman Long wrote:
> Track the number of slowpath locking operations that are being done
> without any MCS node available as well renaming lock_index[123] to make
> them more descriptive.
>
> Using these stat counters is one way to find out if a code path is
> being exercised.
>
> Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
> ---
> kernel/locking/qspinlock.c | 3 ++-
> kernel/locking/qspinlock_stat.h | 21 +++++++++++++++------
> 2 files changed, 17 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
> index 0875053..21ee51b 100644
> --- a/kernel/locking/qspinlock.c
> +++ b/kernel/locking/qspinlock.c
> @@ -422,6 +422,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
> * simple enough.
> */
> if (unlikely(idx >= MAX_NODES)) {
> + qstat_inc(qstat_lock_no_node, true);
> while (!queued_spin_trylock(lock))
> cpu_relax();
> goto release;
> @@ -432,7 +433,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
> /*
> * Keep counts of non-zero index values:
> */
> - qstat_inc(qstat_lock_idx1 + idx - 1, idx);
> + qstat_inc(qstat_lock_use_node2 + idx - 1, idx);
>
> /*
> * Ensure that we increment the head node->count before initialising
> diff --git a/kernel/locking/qspinlock_stat.h b/kernel/locking/qspinlock_stat.h
> index 42d3d8d..31728f6 100644
> --- a/kernel/locking/qspinlock_stat.h
> +++ b/kernel/locking/qspinlock_stat.h
> @@ -30,6 +30,13 @@
> * pv_wait_node - # of vCPU wait's at a non-head queue node
> * lock_pending - # of locking operations via pending code
> * lock_slowpath - # of locking operations via MCS lock queue
> + * lock_use_node2 - # of locking operations that use 2nd percpu node
> + * lock_use_node3 - # of locking operations that use 3rd percpu node
> + * lock_use_node4 - # of locking operations that use 4th percpu node
> + * lock_no_node - # of locking operations without using percpu node
> + *
> + * Subtraccting lock_use_node[234] from lock_slowpath will give you
> + * lock_use_node1.
Typo: "subtraccting"
Will
