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Get() Does Not Reserve space for to_delete memtables 

Summary: It seems to be a decision tradeoff in current codes: we make a malloc for every Get() to reduce one malloc for a flush inside mutex. It takes about 5% of CPU time in readrandom tests. We might consider the tradeoff to be the other way around.

Test Plan: make all check

Reviewers: dhruba, haobo, igor

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14697
This commit is contained in:
Siying Dong 2013-12-17 14:58:42 -08:00
parent 417b453fa6
commit a8b8b11dc4
1 changed files with 0 additions and 2 deletions
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2
db/db_impl.cc
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@ -2597,7 +2597,6 @@ Status DBImpl::GetImpl(const ReadOptions& options,
StopWatch sw(env_, options_.statistics.get(), DB_GET);
SequenceNumber snapshot;
std::vector<MemTable*> to_delete;
to_delete.reserve(options_.max_write_buffer_number);
mutex_.Lock();
if (options.snapshot != nullptr) {
snapshot = reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_;
@ -2665,7 +2664,6 @@ std::vector<Status> DBImpl::MultiGet(const ReadOptions& options,
StopWatch sw(env_, options_.statistics.get(), DB_MULTIGET);
SequenceNumber snapshot;
std::vector<MemTable*> to_delete;
to_delete.reserve(options_.max_write_buffer_number);
mutex_.Lock();
if (options.snapshot != nullptr) {