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

[Jia Guo]

Hi Changwei:

On 2018/10/24 9:21, Changwei Ge wrote:
> Hi Jia,
> 
> Your patch was not made properly and can't be applied to my work tree. :-(
> Please check it.
> 
I'm very sorry that I chose a wrong code path when executing 'git init'. :-(
PATCH V2 will fix it.
> Moreover, I *disagree* with your way trying to boost HB performance.
> Actually, ocfs2 o2cb/heartbeat mechanism reads and writes region according slot number rather
> than cluster node number.(Perhaps I missed something or your patch relies on your other patches)
> And for slot assignment algorithm applied in ocfs2/mounting, the lowest slot number is always the first choice.
> So your patch should not work...
> 
I'm afraid you misunderstood the concept of slot number and heartbeat region. The heartbeat region corresponds to
the cluster node number while the slot number assignment is what you describe.
Thanks,
Jia
> Thanks,
> Changwei
> 
> On 2018/10/23 20:33, 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)
>>   {
>> -	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;
>>
> .
>