Re: [PATCH v2 1/2] ceph: update the __update_latency helper

[Xiubo Li <xiubli@redhat.com>]

On 2021/4/28 2:38, Jeff Layton wrote:
> On Thu, 2021-03-25 at 11:28 +0800, xiubli@redhat.com wrote:
>> From: Xiubo Li <xiubli@redhat.com>
>>
>> Let the __update_latency() helper choose the correcsponding members
>> according to the metric_type.
>>
>> URL: https://tracker.ceph.com/issues/49913
>> Signed-off-by: Xiubo Li <xiubli@redhat.com>
>> ---
>>   fs/ceph/metric.c | 73 ++++++++++++++++++++++++++++++++++--------------
>>   1 file changed, 52 insertions(+), 21 deletions(-)
>>
>> diff --git a/fs/ceph/metric.c b/fs/ceph/metric.c
>> index 28b6b42ad677..f3e68db08760 100644
>> --- a/fs/ceph/metric.c
>> +++ b/fs/ceph/metric.c
>> @@ -285,19 +285,56 @@ void ceph_metric_destroy(struct ceph_client_metric *m)
>>   		ceph_put_mds_session(m->session);
>>   }
>>   
>> -static inline void __update_latency(ktime_t *totalp, ktime_t *lsump,
>> -				    ktime_t *min, ktime_t *max,
>> -				    ktime_t *sq_sump, ktime_t lat)
>> -{
>> -	ktime_t total, avg, sq, lsum;
>> -
>> -	total = ++(*totalp);
>> -	lsum = (*lsump += lat);
>> +typedef enum {
>> +	CEPH_METRIC_READ,
>> +	CEPH_METRIC_WRITE,
>> +	CEPH_METRIC_METADATA,
>> +} metric_type;
>> +
>> +#define METRIC_UPDATE_MIN_MAX(min, max, new)	\
>> +{						\
>> +	if (unlikely(new < min))		\
>> +		min = new;			\
>> +	if (unlikely(new > max))		\
>> +		max = new;			\
>> +}
>>   
>> -	if (unlikely(lat < *min))
>> -		*min = lat;
>> -	if (unlikely(lat > *max))
>> -		*max = lat;
>> +static inline void __update_latency(struct ceph_client_metric *m,
>> +				    metric_type type, ktime_t lat)
>> +{
>> +	ktime_t total, avg, sq, lsum, *sq_sump;
>> +
>> +	switch (type) {
>> +	case CEPH_METRIC_READ:
>> +		total = ++m->total_reads;
>> +		m->read_latency_sum += lat;
>> +		lsum = m->read_latency_sum;
>> +		METRIC_UPDATE_MIN_MAX(m->read_latency_min,
>> +				      m->read_latency_max,
>> +				      lat);
>> +		sq_sump = &m->read_latency_sq_sum;
>> +		break;
>> +	case CEPH_METRIC_WRITE:
>> +		total = ++m->total_writes;
>> +		m->write_latency_sum += lat;
>> +		lsum = m->write_latency_sum;
>> +		METRIC_UPDATE_MIN_MAX(m->write_latency_min,
>> +				      m->write_latency_max,
>> +				      lat);
>> +		sq_sump = &m->write_latency_sq_sum;
>> +		break;
>> +	case CEPH_METRIC_METADATA:
>> +		total = ++m->total_metadatas;
>> +		m->metadata_latency_sum += lat;
>> +		lsum = m->metadata_latency_sum;
>> +		METRIC_UPDATE_MIN_MAX(m->metadata_latency_min,
>> +				      m->metadata_latency_max,
>> +				      lat);
>> +		sq_sump = &m->metadata_latency_sq_sum;
>> +		break;
>> +	default:
>> +		return;
>> +	}
>>   
> I'm not a fan of the above function. __update_latency gets called with
> each of those values only once.
>
> It seems like it'd be better to just open-code the above sections in the
> respective ceph_update_*_metrics functions, and then have a helper
> function for the part of __update_latency below this point. With that,
> you wouldn't need the enum either.

Sounds good to me, will fix it.


>
>>   	if (unlikely(total == 1))
>>   		return;
>> @@ -320,9 +357,7 @@ void ceph_update_read_metrics(struct ceph_client_metric *m,
>>   		return;
>>   
>>   	spin_lock(&m->read_metric_lock);
>> -	__update_latency(&m->total_reads, &m->read_latency_sum,
>> -			 &m->read_latency_min, &m->read_latency_max,
>> -			 &m->read_latency_sq_sum, lat);
>> +	__update_latency(m, CEPH_METRIC_READ, lat);
>>   	spin_unlock(&m->read_metric_lock);
>>   }
>>   
>> @@ -336,9 +371,7 @@ void ceph_update_write_metrics(struct ceph_client_metric *m,
>>   		return;
>>   
>>   	spin_lock(&m->write_metric_lock);
>> -	__update_latency(&m->total_writes, &m->write_latency_sum,
>> -			 &m->write_latency_min, &m->write_latency_max,
>> -			 &m->write_latency_sq_sum, lat);
>> +	__update_latency(m, CEPH_METRIC_WRITE, lat);
>>   	spin_unlock(&m->write_metric_lock);
>>   }
>>   
>> @@ -352,8 +385,6 @@ void ceph_update_metadata_metrics(struct ceph_client_metric *m,
>>   		return;
>>   
>>   	spin_lock(&m->metadata_metric_lock);
>> -	__update_latency(&m->total_metadatas, &m->metadata_latency_sum,
>> -			 &m->metadata_latency_min, &m->metadata_latency_max,
>> -			 &m->metadata_latency_sq_sum, lat);
>> +	__update_latency(m, CEPH_METRIC_METADATA, lat);
>>   	spin_unlock(&m->metadata_metric_lock);
>>   }