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Not scheduling more L1->L2 compaction if L0->L1 is pending with higher priority

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Summary: When L0->L1 is pending, there may be one L1->L2 compaction going on which prevents the L0->L1 compaction from happening. If L1 needs more data to be moved to L2, then we may continue scheduling more L1->L2 compactions. The end result may be that L0->L1 compaction will not happen until L1 size drops to below target size. We can reduce the stalling because of number of L0 files by stopping schedling new L1->L2 compaction when L0's score is higher than L1.

Test Plan: Run all existing tests.

Reviewers: yhchiang, MarkCallaghan, rven, anthony, IslamAbdelRahman, igor

Reviewed By: igor

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D52401
This commit is contained in:
sdong 2016-01-07 18:09:34 -08:00
parent 9a8e3f73ed
commit 235b162be1
2 changed files with 105 additions and 0 deletions
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10
db/compaction_picker.cc
View File

@ -919,11 +919,18 @@ Compaction* LevelCompactionPicker::PickCompaction(
CompactionReason compaction_reason = CompactionReason::kUnknown;
// Find the compactions by size on all levels.
bool skipped_l0 = false;
for (int i = 0; i < NumberLevels() - 1; i++) {
score = vstorage->CompactionScore(i);
level = vstorage->CompactionScoreLevel(i);
assert(i == 0 || score <= vstorage->CompactionScore(i - 1));
if (score >= 1) {
if (skipped_l0 && level == vstorage->base_level()) {
// If L0->base_level compaction is pending, don't schedule further
// compaction from base level. Otherwise L0->base_level compaction
// may starve.
continue;
}
output_level = (level == 0) ? vstorage->base_level() : level + 1;
if (PickCompactionBySize(vstorage, level, output_level, &inputs,
&parent_index, &base_index) &&
@ -940,6 +947,9 @@ Compaction* LevelCompactionPicker::PickCompaction(
} else {
// didn't find the compaction, clear the inputs
inputs.clear();
if (level == 0) {
skipped_l0 = true;
}
}
}
}

95
db/compaction_picker_test.cc
View File

@ -580,6 +580,101 @@ TEST_F(CompactionPickerTest, OverlappingUserKeys3) {
ASSERT_EQ(7U, compaction->input(1, 1)->fd.GetNumber());
}
TEST_F(CompactionPickerTest, NotScheduleL1IfL0WithHigherPri1) {
NewVersionStorage(6, kCompactionStyleLevel);
mutable_cf_options_.level0_file_num_compaction_trigger = 2;
mutable_cf_options_.max_bytes_for_level_base = 900000000U;
// 6 L0 files, score 3.
Add(0, 1U, "000", "400", 1U);
Add(0, 2U, "001", "400", 1U, 0, 0);
Add(0, 3U, "001", "400", 1000000000U, 0, 0);
Add(0, 31U, "001", "400", 1000000000U, 0, 0);
Add(0, 32U, "001", "400", 1000000000U, 0, 0);
Add(0, 33U, "001", "400", 1000000000U, 0, 0);
// L1 total size 2GB, score 2.2. If one file being comapcted, score 1.1.
Add(1, 4U, "050", "300", 1000000000U, 0, 0);
file_map_[4u].first->being_compacted = true;
Add(1, 5U, "301", "350", 1000000000U, 0, 0);
// Output level overlaps with the beginning and the end of the chain
Add(2, 6U, "050", "100", 1U);
Add(2, 7U, "300", "400", 1U);
// No compaction should be scheduled, if L0 has higher priority than L1
// but L0->L1 compaction is blocked by a file in L1 being compacted.
UpdateVersionStorageInfo();
ASSERT_EQ(0, vstorage_->CompactionScoreLevel(0));
ASSERT_EQ(1, vstorage_->CompactionScoreLevel(1));
std::unique_ptr<Compaction> compaction(level_compaction_picker.PickCompaction(
cf_name_, mutable_cf_options_, vstorage_.get(), &log_buffer_));
ASSERT_TRUE(compaction.get() == nullptr);
}
TEST_F(CompactionPickerTest, NotScheduleL1IfL0WithHigherPri2) {
NewVersionStorage(6, kCompactionStyleLevel);
mutable_cf_options_.level0_file_num_compaction_trigger = 2;
mutable_cf_options_.max_bytes_for_level_base = 900000000U;
// 6 L0 files, score 3.
Add(0, 1U, "000", "400", 1U);
Add(0, 2U, "001", "400", 1U, 0, 0);
Add(0, 3U, "001", "400", 1000000000U, 0, 0);
Add(0, 31U, "001", "400", 1000000000U, 0, 0);
Add(0, 32U, "001", "400", 1000000000U, 0, 0);
Add(0, 33U, "001", "400", 1000000000U, 0, 0);
// L1 total size 2GB, score 2.2. If one file being comapcted, score 1.1.
Add(1, 4U, "050", "300", 1000000000U, 0, 0);
Add(1, 5U, "301", "350", 1000000000U, 0, 0);
// Output level overlaps with the beginning and the end of the chain
Add(2, 6U, "050", "100", 1U);
Add(2, 7U, "300", "400", 1U);
// If no file in L1 being compacted, L0->L1 compaction will be scheduled.
UpdateVersionStorageInfo(); // being_compacted flag is cleared here.
ASSERT_EQ(0, vstorage_->CompactionScoreLevel(0));
ASSERT_EQ(1, vstorage_->CompactionScoreLevel(1));
std::unique_ptr<Compaction> compaction(level_compaction_picker.PickCompaction(
cf_name_, mutable_cf_options_, vstorage_.get(), &log_buffer_));
ASSERT_TRUE(compaction.get() != nullptr);
}
TEST_F(CompactionPickerTest, NotScheduleL1IfL0WithHigherPri3) {
NewVersionStorage(6, kCompactionStyleLevel);
mutable_cf_options_.level0_file_num_compaction_trigger = 2;
mutable_cf_options_.max_bytes_for_level_base = 900000000U;
// 6 L0 files, score 3.
Add(0, 1U, "000", "400", 1U);
Add(0, 2U, "001", "400", 1U, 0, 0);
Add(0, 3U, "001", "400", 1000000000U, 0, 0);
Add(0, 31U, "001", "400", 1000000000U, 0, 0);
Add(0, 32U, "001", "400", 1000000000U, 0, 0);
Add(0, 33U, "001", "400", 1000000000U, 0, 0);
// L1 score more than 6.
Add(1, 4U, "050", "300", 1000000000U, 0, 0);
file_map_[4u].first->being_compacted = true;
Add(1, 5U, "301", "350", 1000000000U, 0, 0);
Add(1, 51U, "351", "400", 6000000000U, 0, 0);
// Output level overlaps with the beginning and the end of the chain
Add(2, 6U, "050", "100", 1U);
Add(2, 7U, "300", "400", 1U);
// If score in L1 is larger than L0, L1 compaction goes through despite
// there is pending L0 compaction.
UpdateVersionStorageInfo();
ASSERT_EQ(1, vstorage_->CompactionScoreLevel(0));
ASSERT_EQ(0, vstorage_->CompactionScoreLevel(1));
std::unique_ptr<Compaction> compaction(level_compaction_picker.PickCompaction(
cf_name_, mutable_cf_options_, vstorage_.get(), &log_buffer_));
ASSERT_TRUE(compaction.get() != nullptr);
}
TEST_F(CompactionPickerTest, EstimateCompactionBytesNeeded1) {
int num_levels = ioptions_.num_levels;
ioptions_.level_compaction_dynamic_level_bytes = false;