Re: [PATCH 2/4] ceph: update the __update_latency helper

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2021-03-22 at 20:28 +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 | 58 +++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 42 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/ceph/metric.c b/fs/ceph/metric.c
> index 75d309f2fb0c..d5560ff99a9d 100644
> --- a/fs/ceph/metric.c
> +++ b/fs/ceph/metric.c
> @@ -249,19 +249,51 @@ 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)
> +typedef enum {
> +	CEPH_METRIC_READ,
> +	CEPH_METRIC_WRITE,
> +	CEPH_METRIC_METADATA,
> +} metric_type;
> +
> +static inline void __update_latency(struct ceph_client_metric *m,
> +				    metric_type type, ktime_t lat)
>  {
> +	ktime_t *totalp, *minp, *maxp, *lsump, *sq_sump;
>  	ktime_t total, avg, sq, lsum;
>  
> 
> 
> 
> 
> 
> 
> 
> +	switch (type) {
> +	case CEPH_METRIC_READ:
> +		totalp = &m->total_reads;
> +		lsump = &m->read_latency_sum;
> +		minp = &m->read_latency_min;
> +		maxp = &m->read_latency_max;
> +		sq_sump = &m->read_latency_sq_sum;
> +		break;
> +	case CEPH_METRIC_WRITE:
> +		totalp = &m->total_writes;
> +		lsump = &m->write_latency_sum;
> +		minp = &m->write_latency_min;
> +		maxp = &m->write_latency_max;
> +		sq_sump = &m->write_latency_sq_sum;
> +		break;
> +	case CEPH_METRIC_METADATA:
> +		totalp = &m->total_metadatas;
> +		lsump = &m->metadata_latency_sum;
> +		minp = &m->metadata_latency_min;
> +		maxp = &m->metadata_latency_max;
> +		sq_sump = &m->metadata_latency_sq_sum;
> +		break;
> +	default:
> +		return;
> +	}
> +
>  	total = ++(*totalp);

Why are you adding one to *totalp above? Is that to avoid it being 0? 

>  	lsum = (*lsump += lat);
>  
> 

^^^
Instead of doing all of the above with pointers, why not just add to
total and lsum directly inside the switch statement? This seems like a
lot of pointless indirection.

> 
> 
> 
> 
> 
> -	if (unlikely(lat < *min))
> -		*min = lat;
> -	if (unlikely(lat > *max))
> -		*max = lat;
> +	if (unlikely(lat < *minp))
> +		*minp = lat;
> +	if (unlikely(lat > *maxp))
> +		*maxp = lat;
>  
> 
> 
> 
>  	if (unlikely(total == 1))
>  		return;
> @@ -284,9 +316,7 @@ 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);
>  }
>  
> 
> 
> 
> @@ -300,9 +330,7 @@ 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);
>  }
>  
> 
> 
> 
> @@ -316,8 +344,6 @@ 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);
>  }

-- 
Jeff Layton <jlayton@kernel.org>