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This commit is contained in:
Alexey Milovidov 2021-03-28 04:27:26 +03:00
parent 50f712e198
commit 6f9f7d118d
2 changed files with 6 additions and 3 deletions
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6
programs/server/config.xml
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@ -297,20 +297,22 @@
-->
<mark_cache_size>5368709120</mark_cache_size>
<!-- If you enable the `min_bytes_to_use_mmap_io` setting,
the data in MergeTree tables can be read with mmap to avoid copying from kernel to userspace.
It makes sense only for large files and helps only if data reside in page cache.
To avoid frequent open/mmap/munmap/close calls (which are very expensive due to consequent page faults)
and to reuse mappings from several threads and queries,
the cache of mapped files is maintained. Its size is the number of mapped regions (usually equal to the number of mapped files).
The amount of data in mapped files can be monitored in system.metrics, system.metric_log by the MappedFiles, MappedFileBytes metrics
The amount of data in mapped files can be monitored
in system.metrics, system.metric_log by the MappedFiles, MappedFileBytes metrics
and in system.asynchronous_metrics, system.asynchronous_metrics_log by the MMapCacheCells metric,
and also in system.events, system.processes, system.query_log, system.query_thread_log by the
CreatedReadBufferMMap, CreatedReadBufferMMapFailed, MappedFileCacheHits, MappedFileCacheMisses events.
Note that the amount of data in mapped files does not consume memory directly and is not accounted
in query or server memory usage - because this memory can be discarded similar to OS page cache.
The cache is dropped (the files are closed) automatically on removal of old parts in MergeTree,
also it can be dropped manually by the SYSTEM DROP MMAP CACHE query. Good luck.
also it can be dropped manually by the SYSTEM DROP MMAP CACHE query.
-->
<mmap_cache_size>1000</mmap_cache_size>

3
src/Storages/MergeTree/MergeTreeData.cpp
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@ -1163,7 +1163,8 @@ void MergeTreeData::clearOldPartsFromFilesystem(bool force)
/// This is needed to close files to avoid they reside on disk after being deleted.
/// NOTE: we can drop files from cache more selectively but this is good enough.
global_context.dropMappedFileCache();
if (!parts_to_remove.empty())
global_context.dropMappedFileCache();
}
void MergeTreeData::clearPartsFromFilesystem(const DataPartsVector & parts_to_remove)