c/leader_balancer: replaced muted group index with roaring bitmap #16917
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The muted group index was using a `absl::flat_has_set` the use of flat data structure lead to oversized allocation when the number of muted/skipped raft group was large. Replaced a hash set with roaring bitmap. The roaring bitmap is efficient and compressed leading to better performance and smaller allocation. Fixes: redpanda-data#12005 Signed-off-by: Michal Maslanka <michal@redpanda.com>
StephanDollberg
approved these changes
Mar 7, 2024
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Fixes: #12005
I don't think that fixes that issue actually. The issue in that ticket stems from the random_reassignments constructor where we are constructing the _current_leaders hash map (which has a massive index array).
Our obvious easy fix is to switch it over to a btree map but I had a look at the leader balancer benchmarks and that tanks performance quite considerably (not super surprising).
Hence, we are currently looking in getting a segmented hashmap going that would be perfect for this usecase (and many others in RP). martinus/unordered_dense#112
Nevertheless this fix seems sensible either way so should be good to merge
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/backport v23.3.x |
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/backport v23.2.x |
This was referenced Mar 7, 2024
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The muted group index was using a
absl::flat_has_setthe use of flat data structure lead to oversized allocation when the number of muted/skipped raft group was large. Replaced a hash set with roaring bitmap. The roaring bitmap is efficient and compressed leading to better performance and smaller allocation.Backports Required
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