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678ba5e41c
Summary:
The first parameter of SyncPoint::Process is "const std::string&". The majority, maybe all, of the actual calls to this function use a "const char *". The conversion before entering the function requires a construction of a std::string object on the heap. This std::object is then typically not needed because first use of the string is a rocksdb::Slice which has a less costly conversion of char * to slice.
Example:
We have a load and iterate test. The test loads 10m keys and iterates most via 10 rocksdb::Iterator objects. We used TCMALLOC to gather information about allocation and space usage during iterators.
- Before this PR: test took 32 min 17 sec
- After this PR: test took 1 min 14 sec
The TCMALLOC top object list before this PR:
<pre>
Total: 5105999 objects
5003717 98.0% 98.0% 5009471 98.1% rocksdb::DBIter::MergeValuesNewToOld (inline)
20260 0.4% 98.4% 20260 0.4% std::__cxx11::basic_string::_M_mutate
15214 0.3% 98.7% 15214 0.3% rocksdb::UncompressBlockContentsForCompressionType (inline)
13408 0.3% 99.0% 13408 0.3% std::_Rb_tree::_M_emplace_hint_unique [clone .constprop.416] (inline)
12957 0.3% 99.2% 12957 0.3% std::_Rb_tree::_M_emplace_hint_unique [clone .constprop.405] (inline)
9327 0.2% 99.4% 9327 0.2% std::_Rb_tree::_M_copy (inline)
7691 0.2% 99.5% 9919 0.2% JVM_FindSignal
2859 0.1% 99.6% 2859 0.1% rocksdb::Cleanable::RegisterCleanup
2844 0.1% 99.7% 2844 0.1% std::map::operator[] (inline)
</pre>
The "MergeValuesNewToOld (inline)" objects are the #define wrappers to SyncPoint::Process. We discovered this in a 5.18 rocksdb release. There TCMALLOC was more specific that std::basic_string was being constructed. I believe that was before SyncPoint::Process was declared inline in subsequent releases.
The TCMALLOC top object list after this PR:
<pre>
Total: 104911 objects
45090 43.0% 43.0% 45090 43.0% rocksdb::Cleanable::RegisterCleanup
29995 28.6% 71.6% 29995 28.6% rocksdb::LRUCacheShard::Insert
15229 14.5% 86.1% 15229 14.5% rocksdb::UncompressBlockContentsForCompressionType (inline)
4373 4.2% 90.3% 4551 4.3% JVM_FindSignal
2881 2.7% 93.0% 2881 2.7% rocksdb::::ReadBlockFromFile (inline)
1162 1.1% 94.1% 1176 1.1% rocksdb::BlockFetcher::ReadBlockContents (inline)
1036 1.0% 95.1% 1036 1.0% std::__cxx11::basic_string::_M_mutate
869 0.8% 95.9% 869 0.8% std::vector::_M_realloc_insert (inline)
806 0.8% 96.7% 806 0.8% SnmpAgent::GetVariables (inline)
</pre>
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9023
Reviewed By: pdillinger
Differential Revision: D31610907
Pulled By: mrambacher
fbshipit-source-id: 574ff51b639dd46ad253a8e664a575f06b7cc85d
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|---|---|---|
| .. | ||
| mock_time_env.cc | ||
| mock_time_env.h | ||
| sync_point.cc | ||
| sync_point.h | ||
| sync_point_impl.cc | ||
| sync_point_impl.h | ||
| testharness.cc | ||
| testharness.h | ||
| testutil.cc | ||
| testutil.h | ||
| testutil_test.cc | ||
| transaction_test_util.cc | ||
| transaction_test_util.h | ||