Add premmapped areas to file area freelist.

3 files changed, 89 insertions, 12 deletions

diff --git a/vespalib/src/tests/util/file_area_freelist/file_area_freelist_test.cpp b/vespalib/src/tests/util/file_area_freelist/file_area_freelist_test.cpp
index 9a51be3b817..e844a66f5e9 100644
--- a/vespalib/src/tests/util/file_area_freelist/file_area_freelist_test.cpp
+++ b/vespalib/src/tests/util/file_area_freelist/file_area_freelist_test.cpp
@@ -14,6 +14,7 @@ protected:
 public:
     FileAreaFreeListTest();
     ~FileAreaFreeListTest();
+    void test_merge_area_blocked(bool previous);
 };
 
 FileAreaFreeListTest::FileAreaFreeListTest()
@@ -23,6 +24,24 @@ FileAreaFreeListTest::FileAreaFreeListTest()
 
 FileAreaFreeListTest::~FileAreaFreeListTest() = default;
 
+void
+FileAreaFreeListTest::test_merge_area_blocked(bool previous)
+{
+    _freelist.add_premmapped_area(4, 1);
+    _freelist.add_premmapped_area(5, 1);
+    EXPECT_EQ(4, _freelist.alloc(1));
+    EXPECT_EQ(5, _freelist.alloc(1));
+    if (previous) {
+        _freelist.free(4, 1);
+        _freelist.free(5, 1);
+    } else {
+        _freelist.free(5, 1);
+        _freelist.free(4, 1);
+    }
+    EXPECT_EQ(bad_offset, _freelist.alloc(2));
+    _freelist.remove_premmapped_area(4, 1);
+    _freelist.remove_premmapped_area(5, 1);
+}
 
 TEST_F(FileAreaFreeListTest, empty_freelist_is_ok)
 {
@@ -44,6 +63,11 @@ TEST_F(FileAreaFreeListTest, merge_area_with_next_area)
     EXPECT_EQ(bad_offset, _freelist.alloc(1));
 }
 
+TEST_F(FileAreaFreeListTest, merge_area_with_next_area_blocked_by_fence)
+{
+    test_merge_area_blocked(false);
+}
+
 TEST_F(FileAreaFreeListTest, merge_area_with_previous_area)
 {
     _freelist.free(3, 1);
@@ -52,6 +76,11 @@ TEST_F(FileAreaFreeListTest, merge_area_with_previous_area)
     EXPECT_EQ(bad_offset, _freelist.alloc(1));
 }
 
+TEST_F(FileAreaFreeListTest, merge_area_with_previous_area_blocked_by_fence)
+{
+    test_merge_area_blocked(true);
+}
+
 TEST_F(FileAreaFreeListTest, merge_area_with_previous_and_next_area)
 {
     _freelist.free(5, 1);
diff --git a/vespalib/src/vespa/vespalib/util/file_area_freelist.cpp b/vespalib/src/vespa/vespalib/util/file_area_freelist.cpp
index 4894ddfa2fd..32b58b7e805 100644
--- a/vespalib/src/vespa/vespalib/util/file_area_freelist.cpp
+++ b/vespalib/src/vespa/vespalib/util/file_area_freelist.cpp
@@ -7,11 +7,15 @@ namespace vespalib::alloc {
 
 FileAreaFreeList::FileAreaFreeList()
     : _free_areas(),
-      _free_sizes()
+      _free_sizes(),
+      _fences()
 {
 }
 
-FileAreaFreeList::~FileAreaFreeList() = default;
+FileAreaFreeList::~FileAreaFreeList()
+{
+    assert(_fences.empty());
+}
 
 void
 FileAreaFreeList::remove_from_size_set(uint64_t offset, size_t size)
@@ -73,23 +77,29 @@ FileAreaFreeList::free(uint64_t offset, size_t size)
 {
     auto itr = _free_areas.lower_bound(offset);
     if (itr != _free_areas.end() && itr->first <= offset + size) {
-        // Merge with next free area
         assert(itr->first == offset + size);
-        remove_from_size_set(itr->first, itr->second);
-        size += itr->second;
-        itr = _free_areas.erase(itr);
+        if (!_fences.contains(offset + size)) {
+            // Merge with next free area
+            remove_from_size_set(itr->first, itr->second);
+            size += itr->second;
+            itr = _free_areas.erase(itr);
+        }
     }
     bool adjusted_prev_area = false;
     if (itr != _free_areas.begin()) {
         --itr;
         if (itr->first + itr->second >= offset) {
-            // Merge with previous free area
             assert(itr->first + itr->second == offset);
-            remove_from_size_set(itr->first, itr->second);
-            offset = itr->first;
-            size += itr->second;
-            itr->second = size;
-            adjusted_prev_area = true;
+            if (!_fences.contains(offset)) {
+                // Merge with previous free area
+                remove_from_size_set(itr->first, itr->second);
+                offset = itr->first;
+                size += itr->second;
+                itr->second = size;
+                adjusted_prev_area = true;
+            } else {
+                ++itr;
+            }
         } else {
             ++itr;
         }
@@ -101,4 +111,38 @@ FileAreaFreeList::free(uint64_t offset, size_t size)
     assert(ins_res.second);
 }
 
+void
+FileAreaFreeList::add_premmapped_area(uint64_t offset, size_t size)
+{
+    auto itr = _free_areas.lower_bound(offset);
+    if (itr != _free_areas.end()) {
+        assert(itr->first >= offset + size);
+    }
+    auto ins_res = _free_sizes[size].insert(offset);
+    assert(ins_res.second);
+    _free_areas.emplace_hint(itr, offset, size);
+    auto fences_ins_res = _fences.insert(offset);
+    assert(fences_ins_res.second);
+}
+
+void
+FileAreaFreeList::remove_premmapped_area(uint64_t offset, size_t size)
+{
+    auto itr = _free_areas.lower_bound(offset);
+    assert(itr != _free_areas.end());
+    assert(itr->first == offset);
+    assert(itr->second == size);
+    auto sizes_itr = _free_sizes.lower_bound(size);
+    assert(sizes_itr != _free_sizes.end());
+    assert(sizes_itr->first == size);
+    assert(sizes_itr->second.contains(offset));
+    assert(_fences.contains(offset));
+    _free_areas.erase(itr);
+    sizes_itr->second.erase(offset);
+    if (sizes_itr->second.empty()) {
+        _free_sizes.erase(sizes_itr);
+    }
+    _fences.erase(offset);
+}
+
 }
diff --git a/vespalib/src/vespa/vespalib/util/file_area_freelist.h b/vespalib/src/vespa/vespalib/util/file_area_freelist.h
index 00820c680ed..4982f294289 100644
--- a/vespalib/src/vespa/vespalib/util/file_area_freelist.h
+++ b/vespalib/src/vespa/vespalib/util/file_area_freelist.h
@@ -2,6 +2,7 @@
 
 #pragma once
 
+#include <vespa/vespalib/stllike/hash_set.h>
 #include <cstddef>
 #include <cstdint>
 #include <limits>
@@ -16,6 +17,7 @@ namespace vespalib::alloc {
 class FileAreaFreeList {
     std::map<uint64_t, size_t> _free_areas; // map from offset to size
     std::map<size_t, std::set<uint64_t>> _free_sizes; // map from size to set of offsets
+    vespalib::hash_set<uint64_t> _fences;
     void remove_from_size_set(uint64_t offset, size_t size);
     std::pair<uint64_t, size_t> prepare_reuse_area(size_t size);
 public:
@@ -23,6 +25,8 @@ public:
     ~FileAreaFreeList();
     uint64_t alloc(size_t size);
     void free(uint64_t offset, size_t size);
+    void add_premmapped_area(uint64_t offset, size_t size);
+    void remove_premmapped_area(uint64_t offset, size_t size);
     static constexpr uint64_t bad_offset = std::numeric_limits<uint64_t>::max();
 };