[Ocfs2-devel] [PATCH] ocfs2: Optimize the reading of heartbeat data

[Joseph Qi]

Hi,

On 18/10/23 20:32, Jia Guo wrote:
> Reading heartbeat data from lowest node rather than from zero, in
> cases where the node is not defined from zero, can reduce the number
> of sectors read.
> 
> Here is a simple test data obtained with 'iostat -dmx dm-5 2', with
> two nodes in the cluster, node number 10, 20, respectively.
> Before optimization:
> Device:         rrqm/s   wrqm/s     r/s     w/s    rMB/s    wMB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
> dm-5              0.00     0.00    0.50    0.50     0.01     0.00    11.00     0.00    1.00    1.00    1.00   1.50   0.15
> After the optimization:
> Device:         rrqm/s   wrqm/s     r/s     w/s    rMB/s    wMB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
> dm-5              0.00     0.00    0.50    0.50     0.00     0.00     6.00     0.00    0.50    1.00    0.00   0.50   0.05
> 
> Signed-off-by: Jia Guo <guojia12 at huawei.com>
> Reviewed-by: Jun Piao <piaojun at huawei.com>
> Reviewed-by: Yiwen Jiang <jiangyiwen at huawei.com>
> ---
>  cluster/heartbeat.c | 23 +++++++++++++++--------
>  1 file changed, 15 insertions(+), 8 deletions(-)
> 
> diff --git a/cluster/heartbeat.c b/cluster/heartbeat.c
> index 9b2ed62..a9cf984 100644
> --- a/cluster/heartbeat.c
> +++ b/cluster/heartbeat.c
> @@ -582,17 +582,18 @@ bail:
>  }
> 
>  static int o2hb_read_slots(struct o2hb_region *reg,
> -			   unsigned int max_slots)
> +			   unsigned int min_slot,
> +			   unsigned int max_slot)

I don't think changing max_slots to max_slot here is appropriate.
max_slots stands for number of slots totally, while max_slot stands
for the maximum slot number, corresponding with the minimum slot
number. 
The passing value of the caller hints this.

Thanks,
Joseph

>  {
> -	unsigned int current_slot=0;
> +	unsigned int current_slot = min_slot;
>  	int status;
>  	struct o2hb_bio_wait_ctxt wc;
>  	struct bio *bio;
> 
>  	o2hb_bio_wait_init(&wc);
> 
> -	while(current_slot < max_slots) {
> -		bio = o2hb_setup_one_bio(reg, &wc, &current_slot, max_slots,
> +	while(current_slot < max_slot) {
> +		bio = o2hb_setup_one_bio(reg, &wc, &current_slot, max_slot,
>  					 REQ_OP_READ, 0);
>  		if (IS_ERR(bio)) {
>  			status = PTR_ERR(bio);
> @@ -1093,9 +1094,14 @@ static int o2hb_highest_node(unsigned long *nodes, int numbits)
>  	return find_last_bit(nodes, numbits);
>  }
> 
> +static int o2hb_lowest_node(unsigned long *nodes, int numbits)
> +{
> +	return find_first_bit(nodes, numbits);
> +}
> +
>  static int o2hb_do_disk_heartbeat(struct o2hb_region *reg)
>  {
> -	int i, ret, highest_node;
> +	int i, ret, highest_node, lowest_node;
>  	int membership_change = 0, own_slot_ok = 0;
>  	unsigned long configured_nodes[BITS_TO_LONGS(O2NM_MAX_NODES)];
>  	unsigned long live_node_bitmap[BITS_TO_LONGS(O2NM_MAX_NODES)];
> @@ -1120,7 +1126,8 @@ static int o2hb_do_disk_heartbeat(struct o2hb_region *reg)
>  	}
> 
>  	highest_node = o2hb_highest_node(configured_nodes, O2NM_MAX_NODES);
> -	if (highest_node >= O2NM_MAX_NODES) {
> +	lowest_node = o2hb_lowest_node(configured_nodes, O2NM_MAX_NODES);
> +	if (highest_node >= O2NM_MAX_NODES || lowest_node >= O2NM_MAX_NODES) {
>  		mlog(ML_NOTICE, "o2hb: No configured nodes found!\n");
>  		ret = -EINVAL;
>  		goto bail;
> @@ -1130,7 +1137,7 @@ static int o2hb_do_disk_heartbeat(struct o2hb_region *reg)
>  	 * yet. Of course, if the node definitions have holes in them
>  	 * then we're reading an empty slot anyway... Consider this
>  	 * best-effort. */
> -	ret = o2hb_read_slots(reg, highest_node + 1);
> +	ret = o2hb_read_slots(reg, lowest_node, highest_node + 1);
>  	if (ret < 0) {
>  		mlog_errno(ret);
>  		goto bail;
> @@ -1801,7 +1808,7 @@ static int o2hb_populate_slot_data(struct o2hb_region *reg)
>  	struct o2hb_disk_slot *slot;
>  	struct o2hb_disk_heartbeat_block *hb_block;
> 
> -	ret = o2hb_read_slots(reg, reg->hr_blocks);
> +	ret = o2hb_read_slots(reg, 0, reg->hr_blocks);
>  	if (ret)
>  		goto out;
>