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Do not compensate for rounding error when calculating tier sizes #43

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Merged
merged 1 commit into from
Feb 8, 2022
Merged

Do not compensate for rounding error when calculating tier sizes #43

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6 changes: 0 additions & 6 deletions cachelib/allocator/CacheAllocatorConfig.h
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Original file line number Diff line number Diff line change
Expand Up @@ -883,12 +883,6 @@ CacheAllocatorConfig<T>::getMemoryTierConfigs() const {
sum_sizes += tier_config.getSize();
}

if (size != sum_sizes) {
// Adjust capacity of the last tier to account for rounding error
config.back().setSize(
config.back().getSize() + (getCacheSize() - sum_sizes));
}

return config;
}

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8 changes: 3 additions & 5 deletions cachelib/allocator/tests/MemoryTiersTest.cpp
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Expand Up @@ -52,10 +52,11 @@ class MemoryTiersTest: public AllocatorTest<Allocator> {
size_t sum_ratios = std::accumulate(configs.begin(), configs.end(), 0,
[](const size_t i, const MemoryTierCacheConfig& config) { return i + config.getRatio();});

EXPECT_EQ(sum_sizes, expectedTotalCacheSize);
size_t partition_size = 0, remaining_capacity = actualConfig.getCacheSize();
size_t partition_size = 0;
if (sum_ratios) {
partition_size = actualConfig.getCacheSize() / sum_ratios;
/* Sum of sizes can be lower due to rounding down to partition_size. */
EXPECT_GE(sum_sizes, expectedTotalCacheSize - partition_size);
}

for(auto i = 0; i < configs.size(); ++i) {
Expand All @@ -65,10 +66,7 @@ class MemoryTiersTest: public AllocatorTest<Allocator> {
if (configs[i].getRatio() && (i < configs.size() - 1)) {
EXPECT_EQ(configs[i].getSize(), partition_size * configs[i].getRatio());
}
remaining_capacity -= configs[i].getSize();
}

EXPECT_EQ(remaining_capacity, 0);
}

LruAllocatorConfig createTestCacheConfig(
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