On 01/23/2019 04:23 AM, Will Deacon wrote:
> 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 <long...@redhat.com>
>> ---
>> 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
Thanks for catching that.
Cheers,
Longman
