feat(tiering): Serialize hashes

src/core/compact_object.cc

@@ -1224,11 +1224,13 @@ CompactObj::ExternalRep CompactObj::GetExternalRep() const {
   return static_cast<CompactObj::ExternalRep>(u_.ext_ptr.representation);
 }
 
-void CompactObj::SetCool(size_t offset, uint32_t sz, detail::TieredColdRecord* record) {
+void CompactObj::SetCool(size_t offset, uint32_t sz, ExternalRep rep,
+                         detail::TieredColdRecord* record) {
   // We copy the mask of the "cooled" referenced object because it contains the encoding info.
   SetMeta(EXTERNAL_TAG, record->value.mask_);
 
   u_.ext_ptr.is_cool = 1;
+  u_.ext_ptr.representation = static_cast<uint8_t>(rep);
   u_.ext_ptr.page_offset = offset % 4096;
   u_.ext_ptr.serialized_size = sz;
   u_.ext_ptr.cool_record = record;
@@ -1244,6 +1246,10 @@ auto CompactObj::GetCool() const -> CoolItem {
   return res;
 }
 
+void CompactObj::KeepExternal(size_t offset, size_t sz) {
+  SetExternal(offset, sz, GetExternalRep());
+}
+
 std::pair<size_t, size_t> CompactObj::GetExternalSlice() const {
   DCHECK_EQ(EXTERNAL_TAG, taglen_);
   auto& ext = u_.ext_ptr;

src/core/compact_object.h

@@ -364,7 +364,8 @@ class CompactObj {
   }
 
   // Assigns a cooling record to the object together with its external slice.
-  void SetCool(size_t offset, uint32_t serialized_size, detail::TieredColdRecord* record);
+  void SetCool(size_t offset, uint32_t serialized_size, ExternalRep rep,
+               detail::TieredColdRecord* record);
 
   struct CoolItem {
     uint16_t page_offset;
@@ -376,6 +377,10 @@ class CompactObj {
   // Returns the external data of the object incuding its ColdRecord.
   CoolItem GetCool() const;
 
+  // Prequisite: IsCool() is true.
+  // Keeps cool record only as external value and discard in-memory part.
+  void KeepExternal(size_t offset, size_t sz);
+
   std::pair<size_t, size_t> GetExternalSlice() const;
 
   // Injects either the the raw string (extracted with GetRawString()) or the usual string

src/server/common.cc

@@ -162,7 +162,7 @@ bool ParseDouble(string_view src, double* value) {
 #define ADD(x) (x) += o.x
 
 TieredStats& TieredStats::operator+=(const TieredStats& o) {
-  static_assert(sizeof(TieredStats) == 160);
+  static_assert(sizeof(TieredStats) == 168);
 
   ADD(total_stashes);
   ADD(total_fetches);
@@ -182,6 +182,8 @@ TieredStats& TieredStats::operator+=(const TieredStats& o) {
   ADD(small_bins_cnt);
   ADD(small_bins_entries_cnt);
   ADD(small_bins_filling_bytes);
+  ADD(small_bins_filling_entries_cnt);
+
   ADD(total_stash_overflows);
   ADD(cold_storage_bytes);
   ADD(total_offloading_steps);

src/server/common.h

@@ -91,6 +91,7 @@ struct TieredStats {
   uint64_t small_bins_cnt = 0;
   uint64_t small_bins_entries_cnt = 0;
   size_t small_bins_filling_bytes = 0;
+  size_t small_bins_filling_entries_cnt = 0;
   size_t cold_storage_bytes = 0;
 
   uint64_t clients_throttled = 0;        // current number of throttled clients

src/server/hset_family.cc

@@ -492,6 +492,9 @@ OpResult<uint32_t> OpSet(const OpArgs& op_args, string_view key, CmdArgList valu
 
   op_args.shard->search_indices()->AddDoc(key, op_args.db_cntx, pv);
 
+  if (auto* ts = op_args.shard->tiered_storage(); ts)
+    ts->TryStash(op_args.db_cntx.db_index, key, &pv);
+
   return created;
 }
 

src/server/tiered_storage.cc

@@ -17,16 +17,22 @@
 #include "base/flag_utils.h"
 #include "base/flags.h"
 #include "base/logging.h"
+#include "core/detail/listpack_wrap.h"
 #include "server/common.h"
 #include "server/db_slice.h"
 #include "server/engine_shard_set.h"
 #include "server/snapshot.h"
 #include "server/table.h"
 #include "server/tiering/common.h"
 #include "server/tiering/op_manager.h"
+#include "server/tiering/serialized_map.h"
 #include "server/tiering/small_bins.h"
 #include "server/tx_base.h"
 
+extern "C" {
+#include "redis/listpack.h"
+}
+
 using namespace facade;
 
 using AtLeast64 = base::ConstrainedNumericFlagValue<size_t, 64>;  // ABSL_FLAG breaks with commas
@@ -46,6 +52,8 @@ ABSL_FLAG(float, tiered_offload_threshold, 0.5,
 ABSL_FLAG(float, tiered_upload_threshold, 0.1,
           "Ratio of free memory (free/max memory) below which uploading stops");
 
+ABSL_FLAG(bool, tiered_experimental_hash_support, false, "Experimental hash datatype offloading");
+
 namespace dfly {
 
 using namespace std;
@@ -73,6 +81,58 @@ tiering::DiskSegment FromCoolItem(const PrimeValue::CoolItem& item) {
   return {item.record->page_index * tiering::kPageSize + item.page_offset, item.serialized_size};
 }
 
+// Determine required byte size and encoding type based on value.
+// TODO(vlad): Maybe split into different accessors?
+// Do NOT enforce rules depending on dynamic runtime values as this is called
+// when scheduling stash and just before succeeeding and is expected to return the same results
+optional<pair<size_t /*size*/, CompactObj::ExternalRep>> EstimateSerializedSize(
+    const PrimeValue& pv) {
+  switch (pv.ObjType()) {
+    case OBJ_STRING:
+      return std::make_pair(pv.GetRawString().view().size(), CompactObj::ExternalRep::STRING);
+    case OBJ_HASH:
+      if (pv.Encoding() == kEncodingListPack) {
+        auto* lp = static_cast<uint8_t*>(pv.RObjPtr());
+        size_t bytes = lpBytes(lp);
+        bytes += lpLength(lp) * 2 * 4;
+        return std::make_pair(bytes, CompactObj::ExternalRep::SERIALIZED_MAP);
+      }
+      return {};
+    default:
+      return {};
+  };
+}
+
+size_t Serialize(CompactObj::ExternalRep rep, const PrimeValue& pv, io::MutableBytes buffer) {
+  DCHECK_LE(EstimateSerializedSize(pv)->first, buffer.size());
+  switch (rep) {
+    case CompactObj::ExternalRep::STRING: {
+      auto sv = pv.GetRawString();
+      memcpy(buffer.data(), sv.view().data(), sv.view().size());
+      return sv.view().size();
+    }
+    case CompactObj::ExternalRep::SERIALIZED_MAP: {
+      DCHECK_EQ(pv.Encoding(), kEncodingListPack);
+
+      // TODO(vlad): Optimize copy for serialization
+      detail::ListpackWrap lw{static_cast<uint8_t*>(pv.RObjPtr())};
+      vector<pair<string, string>> entries(lw.begin(), lw.end());
+      return tiering::SerializedMap::Serialize(
+          entries, {reinterpret_cast<char*>(buffer.data()), buffer.length()});
+    }
+  };
+  return 0;
+}
+
+string SerializeString(const PrimeValue& pv) {
+  auto estimate = EstimateSerializedSize(pv);
+  string s(estimate->first, 0);
+  size_t written =
+      Serialize(estimate->second, pv, {reinterpret_cast<uint8_t*>(s.data()), s.size()});
+  s.resize(written);
+  return s;
+}
+
 }  // anonymous namespace
 
 class TieredStorage::ShardOpManager : public tiering::OpManager {
@@ -133,12 +193,20 @@ class TieredStorage::ShardOpManager : public tiering::OpManager {
   void RetireColdEntries(size_t additional_memory);
 
   // Set value to be an in-memory type again. Update memory stats.
-  void Upload(DbIndex dbid, string_view value, bool is_raw, size_t serialized_len, PrimeValue* pv) {
+  void Upload(DbIndex dbid, string_view value, PrimeValue* pv) {
     DCHECK(!value.empty());
     DCHECK_EQ(uint8_t(pv->GetExternalRep()), uint8_t(CompactObj::ExternalRep::STRING));
 
-    pv->Materialize(value, is_raw);
-    RecordDeleted(*pv, serialized_len, GetDbTableStats(dbid));
+    switch (pv->GetExternalRep()) {
+      case CompactObj::ExternalRep::STRING:
+        pv->Materialize(value, true);
+        break;
+      case CompactObj::ExternalRep::SERIALIZED_MAP:
+        pv->InitRobj(OBJ_HASH, kEncodingListPack, nullptr);
+        break;
+    };
+
+    RecordDeleted(*pv, value.size(), GetDbTableStats(dbid));
   }
 
   // Find entry by key in db_slice and store external segment in place of original value.
@@ -153,12 +221,13 @@ class TieredStorage::ShardOpManager : public tiering::OpManager {
       stats->tiered_used_bytes += segment.length;
       stats_.total_stashes++;
 
+      CompactObj::ExternalRep rep = EstimateSerializedSize(*pv)->second;
       if (ts_->config_.experimental_cooling) {
         RetireColdEntries(pv->MallocUsed());
-        ts_->CoolDown(key.first, key.second, segment, pv);
+        ts_->CoolDown(key.first, key.second, segment, rep, pv);
       } else {
         stats->AddTypeMemoryUsage(pv->ObjType(), -pv->MallocUsed());
-        pv->SetExternal(segment.offset, segment.length, CompactObj::ExternalRep::STRING);
+        pv->SetExternal(segment.offset, segment.length, rep);
       }
     } else {
       LOG(DFATAL) << "Should not reach here";
@@ -215,7 +284,7 @@ void TieredStorage::ShardOpManager::Defragment(tiering::DiskSegment segment, str
     } else {
       // Cut out relevant part of value and restore it to memory
       string_view value = page.substr(item_segment.offset - segment.offset, item_segment.length);
-      Upload(dbid, value, true, item_segment.length, &pv);
+      Upload(dbid, value, &pv);
     }
   }
 }
@@ -386,36 +455,40 @@ std::optional<util::fb2::Future<bool>> TieredStorage::TryStash(DbIndex dbid, str
     return {};
   }
 
-  StringOrView raw_string = value->GetRawString();
-  value->SetStashPending(true);
+  auto estimated = EstimateSerializedSize(*value);
+  DCHECK(estimated);
 
   tiering::OpManager::EntryId id;
   error_code ec;
 
-  // TODO(vlad): Replace with encoders for different types
-  auto stash_string = [&](std::string_view str) {
-    if (auto prepared = op_manager_->PrepareStash(str.size()); prepared) {
+  value->SetStashPending(true);
+  if (OccupiesWholePages(estimated->first)) {  // large enough for own page
+    id = KeyRef(dbid, key);
+    if (auto prepared = op_manager_->PrepareStash(estimated->first); prepared) {
       auto [offset, buf] = *prepared;
-      memcpy(buf.bytes.data(), str.data(), str.size());
-      tiering::DiskSegment segment{offset, str.size()};
+      size_t written = Serialize(estimated->second, *value, buf.bytes);
+      tiering::DiskSegment segment{offset, written};
       op_manager_->Stash(id, segment, buf);
     } else {
       ec = prepared.error();
     }
-  };
-
-  if (OccupiesWholePages(value->Size())) {  // large enough for own page
-    id = KeyRef(dbid, key);
-    stash_string(raw_string.view());
-  } else if (auto bin = bins_->Stash(dbid, key, raw_string.view()); bin) {
+  } else if (auto bin = bins_->Stash(dbid, key, SerializeString(*value)); bin) {
     id = bin->first;
     // TODO(vlad): Write bin to prepared buffer instead of allocating one
-    stash_string(bin->second);
+    if (auto prepared = op_manager_->PrepareStash(estimated->first); prepared) {
+      auto [offset, buf] = *prepared;
+      memcpy(buf.bytes.data(), bin->second.data(), bin->second.size());
+      tiering::DiskSegment segment{offset, bin->second.size()};
+      op_manager_->Stash(id, segment, buf);
+    } else {
+      ec = prepared.error();
+    }
   } else {
     return {};  // silently added to bin
   }
 
   if (ec) {
+    value->SetStashPending(false);
     LOG_IF(ERROR, ec != errc::file_too_large) << "Stash failed immediately" << ec.message();
     visit([this](auto id) { op_manager_->ClearIoPending(id); }, id);
     return {};
@@ -489,6 +562,7 @@ TieredStats TieredStorage::GetStats() const {
     stats.small_bins_cnt = bins_stats.stashed_bins_cnt;
     stats.small_bins_entries_cnt = bins_stats.stashed_entries_cnt;
     stats.small_bins_filling_bytes = bins_stats.current_bin_bytes;
+    stats.small_bins_filling_entries_cnt = bins_stats.current_entries_cnt;
   }
 
   {  // Own stats
@@ -513,13 +587,14 @@ void TieredStorage::UpdateFromFlags() {
       .write_depth_limit = absl::GetFlag(FLAGS_tiered_storage_write_depth),
       .offload_threshold = absl::GetFlag(FLAGS_tiered_offload_threshold),
       .upload_threshold = absl::GetFlag(FLAGS_tiered_upload_threshold),
+      .experimental_hash_offload = absl::GetFlag(FLAGS_tiered_experimental_hash_support),
   };
 }
 
 std::vector<std::string> TieredStorage::GetMutableFlagNames() {
   return base::GetFlagNames(FLAGS_tiered_min_value_size, FLAGS_tiered_experimental_cooling,
                             FLAGS_tiered_storage_write_depth, FLAGS_tiered_offload_threshold,
-                            FLAGS_tiered_upload_threshold);
+                            FLAGS_tiered_upload_threshold, FLAGS_tiered_experimental_hash_support);
 }
 
 bool TieredStorage::ShouldOffload() const {
@@ -596,10 +671,10 @@ size_t TieredStorage::ReclaimMemory(size_t goal) {
                            ->prime.FindFirst(record->key_hash, predicate);
     CHECK(IsValid(it));
     PrimeValue& pv = it->second;
-    tiering::DiskSegment segment = FromCoolItem(pv.GetCool());
 
     // Now the item is only in storage.
-    pv.SetExternal(segment.offset, segment.length, CompactObj::ExternalRep::STRING);
+    tiering::DiskSegment segment = FromCoolItem(pv.GetCool());
+    pv.KeepExternal(segment.offset, segment.length);
 
     auto* stats = op_manager_->GetDbTableStats(record->db_index);
     stats->AddTypeMemoryUsage(record->value.ObjType(), -record->value.MallocUsed());
@@ -610,14 +685,28 @@ size_t TieredStorage::ReclaimMemory(size_t goal) {
 }
 
 bool TieredStorage::ShouldStash(const PrimeValue& pv) const {
+  // Check value state
+  if (pv.IsExternal() || pv.HasStashPending())
+    return false;
+
+  // Estimate value size
+  auto estimation = EstimateSerializedSize(pv);
+  if (!estimation)
+    return false;
+
+  // For now, hash offloading is conditional
+  if (pv.ObjType() == OBJ_HASH && !config_.experimental_hash_offload)
+    return false;
+
   const auto& disk_stats = op_manager_->GetStats().disk_stats;
-  return !pv.IsExternal() && !pv.HasStashPending() && pv.ObjType() == OBJ_STRING &&
-         pv.Size() >= config_.min_value_size &&
-         disk_stats.allocated_bytes + tiering::kPageSize + pv.Size() < disk_stats.max_file_size;
+  return estimation->first >= config_.min_value_size &&
+         disk_stats.allocated_bytes + tiering::kPageSize + estimation->first <
+             disk_stats.max_file_size;
 }
 
 void TieredStorage::CoolDown(DbIndex db_ind, std::string_view str,
-                             const tiering::DiskSegment& segment, PrimeValue* pv) {
+                             const tiering::DiskSegment& segment, CompactObj::ExternalRep rep,
+                             PrimeValue* pv) {
   detail::TieredColdRecord* record = CompactObj::AllocateMR<detail::TieredColdRecord>();
   cool_queue_.push_front(*record);
   stats_.cool_memory_used += (sizeof(detail::TieredColdRecord) + pv->MallocUsed());
@@ -627,7 +716,7 @@ void TieredStorage::CoolDown(DbIndex db_ind, std::string_view str,
   record->page_index = segment.offset / tiering::kPageSize;
   record->value = std::move(*pv);
 
-  pv->SetCool(segment.offset, segment.length, record);
+  pv->SetCool(segment.offset, segment.length, rep, record);
 }
 
 PrimeValue TieredStorage::Warmup(DbIndex dbid, PrimeValue::CoolItem item) {
@@ -636,10 +725,6 @@ PrimeValue TieredStorage::Warmup(DbIndex dbid, PrimeValue::CoolItem item) {
   // We remove it from both cool storage and the offline storage.
   PrimeValue hot = DeleteCool(item.record);
   op_manager_->DeleteOffloaded(dbid, segment);
-
-  // Bring it back to the PrimeTable.
-  DCHECK(hot.ObjType() == OBJ_STRING);
-
   return hot;
 }
 

src/server/tiered_storage.h

@@ -116,7 +116,7 @@ class TieredStorage {
 
   // Moves pv contents to the cool storage and updates pv to point to it.
   void CoolDown(DbIndex db_ind, std::string_view str, const tiering::DiskSegment& segment,
-                PrimeValue* pv);
+                CompactObj::ExternalRep rep, PrimeValue* pv);
 
   PrimeValue DeleteCool(detail::TieredColdRecord* record);
   detail::TieredColdRecord* PopCool();
@@ -138,6 +138,7 @@ class TieredStorage {
     unsigned write_depth_limit;
     float offload_threshold;
     float upload_threshold;
+    bool experimental_hash_offload;
   } config_;
   struct {
     uint64_t stash_overflow_cnt = 0;