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https://issues.apache.org/jira/browse/HBASE-17515?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15840131#comment-15840131
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Ted Yu commented on HBASE-17515:
--------------------------------
bq. aren't you supposed to multiple by 15, the number of regions to keep around
Clarification about the 15 (default value for
hbase.master.balancer.stochastic.numRegionLoadsToRemember).
See the code in StochasticLoadBalancer#updateRegionLoad() :
{code}
for (Entry<byte[], RegionLoad> entry : sl.getRegionsLoad().entrySet()) {
Deque<BalancerRegionLoad> rLoads =
oldLoads.get(Bytes.toString(entry.getKey()));
if (rLoads == null) {
// There was nothing there
rLoads = new ArrayDeque<BalancerRegionLoad>();
} else if (rLoads.size() >= numRegionLoadsToRemember) {
{code}
For each region, there is a Deque which keeps 15 RegionLoad's.
So 15 is per region, not the number of regions to keep around.
I am collecting size comparison data through Instrumentation. Will be back with
more response.
> Reduce memory footprint of RegionLoads kept by StochasticLoadBalancer
> ---------------------------------------------------------------------
>
> Key: HBASE-17515
> URL: https://issues.apache.org/jira/browse/HBASE-17515
> Project: HBase
> Issue Type: Improvement
> Reporter: Ted Yu
> Assignee: Tim Brown
> Fix For: 2.0.0, 1.4.0
>
> Attachments: 17515.branch-1.v2.txt, 17515.v1.txt, 17515.v2.txt
>
>
> Currently StochasticLoadBalancer uses the following fields of RegionLoad :
> {code}
> return rl.getReadRequestsCount();
> return rl.getWriteRequestsCount();
> return rl.getMemStoreSizeMB();
> return rl.getStorefileSizeMB();
> {code}
> However, RegionLoad refers to ClusterStatusProtos.RegionLoad which has 18
> fields.
> This means we keep hbase.master.balancer.stochastic.numRegionLoadsToRemember
> (default value 15) RegionLoad's in memory but only use a small portion of
> them.
> This JIRA is to consider creating POJO which wraps the above 4 fields so that
> the memory footprint can be lowered.
> Lowering memory footprint would allow wider sliding window to be configured
> for load balancer while limiting the impact to heap consumption.
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