Cache simulator: Add a ghost cache for admission control and a hybrid row-block cache. #5534

HaoyuHuang · 2019-07-02T23:48:07Z

This PR adds a ghost cache for admission control. Specifically, it admits an entry on its second access.
It also adds a hybrid row-block cache that caches the referenced key-value pairs of a Get/MultiGet request instead of its blocks.

Test plan: make clean && COMPILE_WITH_ASAN=1 make check -j32

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@HaoyuHuang has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

facebook-github-bot · 2019-07-08T22:55:41Z

@HaoyuHuang has updated the pull request. Re-import the pull request

…licies.

facebook-github-bot · 2019-07-10T18:20:25Z

@HaoyuHuang has updated the pull request. Re-import the pull request

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riversand963

Took a pass and left a few comments.

riversand963 · 2019-07-10T21:42:37Z

utilities/simulator_cache/cache_simulator.cc

@@ -50,24 +181,48 @@ BlockCacheTraceSimulator::BlockCacheTraceSimulator(
      cache_configurations_(cache_configurations) {}

 Status BlockCacheTraceSimulator::InitializeCaches() {
+  const std::string ghost_cache_prefix = "ghost_";


Is it worth renaming to kGhostCachePrefix?

Sure. I renamed it.

utilities/simulator_cache/cache_simulator.h

riversand963 · 2019-07-10T21:56:29Z

utilities/simulator_cache/cache_simulator.cc

-  uint64_t accesses = hits + misses;
-  return static_cast<double>(misses * 100.0 / accesses);
+void PrioritizedCacheSimulator::Access(const BlockCacheTraceRecord& access) {
+  bool is_cache_miss;


NIt: initialize to avoid linter warning.

Initialized.

utilities/simulator_cache/cache_simulator.h

riversand963 · 2019-07-11T00:47:29Z

utilities/simulator_cache/cache_simulator.h

+    user_accesses_ = 0;
+    user_misses_ = 0;
+  }
+  double miss_ratio() {


Make it const?

I added const for all functions that do not update member variables.

riversand963 · 2019-07-11T00:47:42Z

utilities/simulator_cache/cache_simulator.h

+    }
+    return static_cast<double>(num_misses_ * 100.0 / num_accesses_);
+  }
+  uint64_t total_accesses() { return num_accesses_; }


Make it const?

I added const for all functions that do not update member variables.

riversand963 · 2019-07-11T00:48:47Z

utilities/simulator_cache/cache_simulator.h

+  }
+  uint64_t total_accesses() { return num_accesses_; }
+
+  double user_miss_ratio() {


Make it const?

I added const for all functions that do not update member variables.

riversand963 · 2019-07-11T00:48:55Z

utilities/simulator_cache/cache_simulator.h

+    }
+    return static_cast<double>(user_misses_ * 100.0 / user_accesses_);
+  }
+  uint64_t user_accesses() { return user_accesses_; }


I added const for all functions that do not update member variables.

riversand963 · 2019-07-11T00:49:11Z

utilities/simulator_cache/cache_simulator.h

+                    bool is_user_access, bool* is_cache_miss, bool* admitted,
+                    bool update_metrics);
+
+  Cache::Priority ComputeBlockPriority(const BlockCacheTraceRecord& access);


Make it const?

I added const for all functions that do not update member variables.

riversand963 · 2019-07-11T00:55:29Z

utilities/simulator_cache/cache_simulator_test.cc

+const uint64_t kGhostCacheSize = 1024 * 1024;
+}  // namespace
+
+class CacheSimulatorTest : public DBTestBase {


Looks like the base class does not have to be DBTestBase since many of its database operations, e.g. Open, Close, Put, Flush, etc. are not needed. Maybe consider use testing::Test or testing::WithParamInterface?

Thanks. I changed to testing::Test.

facebook-github-bot · 2019-07-11T03:35:47Z

@HaoyuHuang has updated the pull request. Re-import the pull request

riversand963

LGTM with a few comments.

riversand963 · 2019-07-11T06:47:50Z

Makefile

@@ -1321,7 +1321,7 @@ backupable_db_test: utilities/backupable/backupable_db_test.o $(LIBOBJECTS) $(TE
 checkpoint_test: utilities/checkpoint/checkpoint_test.o $(LIBOBJECTS) $(TESTHARNESS)
 	$(AM_LINK)

-cache_simulator_test: utilities/simulator_cache/cache_simulator_test.o db/db_test_util.o $(LIBOBJECTS) $(TESTHARNESS)
+cache_simulator_test: utilities/simulator_cache/cache_simulator_test.o $(LIBOBJECTS) $(TESTHARNESS)


Nice catch. This can easily be forgotten.

riversand963 · 2019-07-11T15:49:11Z

utilities/simulator_cache/cache_simulator.h

+  };
+
+  // A map stores get_id to a map of row keys. For each row key, it stores a
+  // pair of booleans. The first bool is true when we observe a miss upon the


Looks like it's not a pair of booleans. It's a boolean and an enum.

I updated the comment.

riversand963 · 2019-07-11T16:01:35Z

utilities/simulator_cache/cache_simulator.cc

-    sim_cache_->Insert(access.block_key, /*value=*/nullptr, access.block_size,
-                       /*deleter=*/nullptr, /*handle=*/nullptr);
+  if (handle != nullptr) {
+    sim_cache_->Release(handle);


Can you remind me of why release the handle upon a hit?

The reason is that each entry maintains a ref counter. It is incremented by one inside the lookup so we need to call Release to decrement the ref count.

facebook-github-bot · 2019-07-11T18:24:37Z

@HaoyuHuang has updated the pull request. Re-import the pull request

facebook-github-bot

@HaoyuHuang has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

facebook-github-bot · 2019-07-11T20:12:04Z

@HaoyuHuang merged this pull request in 1a59b6e.

… row-block cache. (facebook#5534) Summary: This PR adds a ghost cache for admission control. Specifically, it admits an entry on its second access. It also adds a hybrid row-block cache that caches the referenced key-value pairs of a Get/MultiGet request instead of its blocks. Pull Request resolved: facebook#5534 Test Plan: make clean && COMPILE_WITH_ASAN=1 make check -j32 Differential Revision: D16101124 Pulled By: HaoyuHuang fbshipit-source-id: b99edda6418a888e94eb40f71ece45d375e234b1

facebook-github-bot added the CLA Signed label Jul 2, 2019

HaoyuHuang requested a review from riversand963 July 2, 2019 23:54

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HaoyuHuang added the WIP Work in progress label Jul 8, 2019

HaoyuHuang added 3 commits July 8, 2019 11:38

Cache simulator: Add a ghost cache for admission control.

afa2355

Add more tests

b1a3b72

Add hybrid row-block cache

c3a11ed

HaoyuHuang force-pushed the cache_admission_control branch from 26cd6a4 to c3a11ed Compare July 8, 2019 22:55

HaoyuHuang removed the WIP Work in progress label Jul 8, 2019

HaoyuHuang changed the title ~~Cache simulator: Add a ghost cache for admission control.~~ Cache simulator: Add a ghost cache for admission control and a hybrid row-block cache. Jul 8, 2019

Ensure hybrid maintains the same total number of accesses as other po…

47e507d

…licies.

facebook-github-bot reviewed Jul 10, 2019

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riversand963 reviewed Jul 11, 2019

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HaoyuHuang requested a review from riversand963 July 11, 2019 03:36

riversand963 approved these changes Jul 11, 2019

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facebook-github-bot closed this in 1a59b6e Jul 11, 2019

facebook-github-bot added the Merged label Jul 11, 2019

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Cache simulator: Add a ghost cache for admission control and a hybrid row-block cache. #5534

Cache simulator: Add a ghost cache for admission control and a hybrid row-block cache. #5534

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Cache simulator: Add a ghost cache for admission control and a hybrid row-block cache. #5534

Cache simulator: Add a ghost cache for admission control and a hybrid row-block cache. #5534

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