remove unnecessary code in super version getter #11452
Closed
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
I don't think this is true though: if a thread completes |
I tend to agree with this. For the local handle to be outdated, a new superversion needs to be installed (specifically, Line 1240 in 509116c in which case the local handle seems up-to-date enough. |
|
@cbi42 has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator. |
|
@cbi42 yeah! The read-write competition is(and should be) resolved by the atomic instruction conducted on the thread local handle, rather than the global superversion number. |
|
@ywave620 has updated the pull request. You must reimport the pull request before landing. |
cbi42
approved these changes
May 22, 2023
cbi42
approved these changes
May 22, 2023
@ywave620 Could you update the PR description accordingly? |
|
@cbi42 Done. PTAL :) |
|
@ywave620 has updated the pull request. You must reimport the pull request before landing. |
|
@cbi42 has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator. |
facebook-github-bot
pushed a commit
that referenced
this pull request
Sep 18, 2023
…#11848) Summary: CI has been hitting assertion error like ``` #8 0x00007fafd9294fd6 in __GI___assert_fail (assertion=assertion@entry=0x7fafda270300 "!*memtable_range_tombstone_iter_ || sv_number_ != cfd_->GetSuperVersionNumber()", file=file@entry=0x7fafda270350 "db/arena_wrapped_db_iter.cc", line=line@entry=124, function=function@entry=0x7fafda270288 "virtual rocksdb::Status rocksdb::ArenaWrappedDBIter::Refresh(const rocksdb::Snapshot*)") at assert.c:101 ``` This is due to * Iterator::Refresh() passing in `cur_sv_number` instead of `sv->version_number` here: https://github.com/facebook/rocksdb/blob/1c6faf35871a236222bcbf0b69718ee43376a951/db/arena_wrapped_db_iter.cc#L94-L96 * `super_version_number_` can be incremented before thread local SV is installed: https://github.com/facebook/rocksdb/blob/main/db/column_family.cc#L1287-L1306 * The optimization in #11452 removed the check for SV number, such that `cur_sv_number > sv.version_number` is possible in the following code. ``` uint64_t cur_sv_number = cfd_->GetSuperVersionNumber(); SuperVersion* sv = cfd_->GetReferencedSuperVersion(db_impl_); ``` Not sure why assertion only started failing after #10594, maybe it's because Refresh() is called more often in stress test. Pull Request resolved: #11848 Test Plan: * This repros hits the assertion pretty consistently before this change: ``` ./db_stress --acquire_snapshot_one_in=10000 --adaptive_readahead=1 --allow_data_in_errors=True --async_io=0 --atomic_flush=1 --auto_readahead_size=1 --avoid_flush_during_recovery=0 --avoid_unnecessary_blocking_io=1 --backup_one_in=0 --block_size=16384 --bloom_bits=0.7161318870366848 --cache_index_and_filter_blocks=0 --cache_size=8388608 --charge_table_reader=0 --checkpoint_one_in=1000000 --checksum_type=kxxHash --clear_column_family_one_in=0 --compact_files_one_in=1000000 --compact_range_one_in=1000000 --compaction_pri=3 --compaction_readahead_size=0 --compaction_ttl=0 --compression_checksum=0 --compression_max_dict_buffer_bytes=0 --compression_max_dict_bytes=0 --compression_parallel_threads=1 --compression_type=zlib --compression_use_zstd_dict_trainer=0 --compression_zstd_max_train_bytes=0 --continuous_verification_interval=0 --data_block_index_type=0 --db_write_buffer_size=8388608 --delpercent=4 --delrangepercent=1 --destroy_db_initially=1 --detect_filter_construct_corruption=0 --disable_wal=1 --enable_compaction_filter=0 --enable_pipelined_write=0 --enable_thread_tracking=1 --fail_if_options_file_error=0 --fifo_allow_compaction=1 --file_checksum_impl=none --flush_one_in=1000000 --format_version=5 --get_current_wal_file_one_in=0 --get_live_files_one_in=1000000 --get_property_one_in=1000000 --get_sorted_wal_files_one_in=0 --index_block_restart_interval=14 --index_type=2 --ingest_external_file_one_in=0 --initial_auto_readahead_size=524288 --iterpercent=30 --key_len_percent_dist=1,30,69 --level_compaction_dynamic_level_bytes=1 --lock_wal_one_in=1000000 --long_running_snapshots=1 --manual_wal_flush_one_in=0 --mark_for_compaction_one_file_in=0 --max_auto_readahead_size=524288 --max_background_compactions=20 --max_bytes_for_level_base=10485760 --max_key=2500000 --max_key_len=3 --max_manifest_file_size=1073741824 --max_write_batch_group_size_bytes=16777216 --max_write_buffer_number=3 --max_write_buffer_size_to_maintain=1048576 --memtable_max_range_deletions=0 --memtable_prefix_bloom_size_ratio=0.5 --memtable_protection_bytes_per_key=0 --memtable_whole_key_filtering=1 --memtablerep=skip_list --min_write_buffer_number_to_merge=1 --mmap_read=1 --mock_direct_io=False --nooverwritepercent=1 --num_file_reads_for_auto_readahead=1 --open_files=500000 --ops_per_thread=100000000 --optimize_filters_for_memory=1 --paranoid_file_checks=0 --partition_filters=0 --partition_pinning=3 --pause_background_one_in=1000000 --periodic_compaction_seconds=0 --prefix_size=-1 --prefixpercent=0 --prepopulate_block_cache=0 --preserve_internal_time_seconds=0 --progress_reports=0 --read_fault_one_in=32 --readahead_size=16384 --readpercent=30 --recycle_log_file_num=1 --reopen=0 --ribbon_starting_level=999 --secondary_cache_fault_one_in=0 --secondary_cache_uri= --set_options_one_in=10000 --snapshot_hold_ops=100000 --sst_file_manager_bytes_per_sec=104857600 --sst_file_manager_bytes_per_truncate=0 --stats_dump_period_sec=600 --subcompactions=1 --sync=0 --sync_fault_injection=1 --target_file_size_base=2097152 --target_file_size_multiplier=2 --test_batches_snapshots=0 --test_cf_consistency=1 --top_level_index_pinning=3 --unpartitioned_pinning=3 --use_direct_io_for_flush_and_compaction=0 --use_direct_reads=0 --use_full_merge_v1=0 --use_get_entity=0 --use_merge=0 --use_multi_get_entity=0 --use_multiget=1 --use_put_entity_one_in=0 --user_timestamp_size=0 --value_size_mult=32 --verification_only=0 --verify_checksum=1 --verify_checksum_one_in=1000000 --verify_db_one_in=100000 --verify_file_checksums_one_in=0 --verify_sst_unique_id_in_manifest=1 --wal_bytes_per_sync=0 --wal_compression=none --write_buffer_size=1048576 --write_dbid_to_manifest=1 --write_fault_one_in=0 --writepercent=35 --use_io_uring=0 --db=/tmp/rocksdb_crashtest_blackboxnf3pyv_0 --expected_values_dir=/tmp/rocksdb_crashtest_expected_6opy9nqg ``` Reviewed By: ajkr Differential Revision: D49344066 Pulled By: cbi42 fbshipit-source-id: d5373ddb48d933acb42a5dd8fae3f3019b0241e5
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Do not bother comparing the version of the local super version handle with the global one.
An inequality comparison result indicates nothing but a spurious obsoleteness. It only happens when the writer has increased the
ColumnFamilyData::super_version_number_(rocksdb/db/column_family.cc
Line 1309 in 5fc57ee
ResetThreadLocalSuperVersions()(rocksdb/db/column_family.cc
Line 1328 in 5fc57ee
void* ptr = local_sv_->Swap(SuperVersion::kSVInUse);). In other words, the existence of a local handle is a sufficent evidence of its fressness.With this PR, we save one or even two atomic instructions when getting a handle of super version.