diff --git a/Makefile b/Makefile
index 4d34b940..b9dac358 100644
--- a/Makefile
+++ b/Makefile
@@ -7,4 +7,4 @@ crc32c.o: crc32c.c
 %.o: %.cpp blockstore.h
 	g++ -Wall -Wno-sign-compare -Wno-parentheses -c -o $@ $<
 test: test.cpp
-	g++ -o test -luring test.cpp
+	g++ -O3 -o test -luring test.cpp
diff --git a/blockstore.h b/blockstore.h
index bdb0fb8f..34917e30 100644
--- a/blockstore.h
+++ b/blockstore.h
@@ -13,7 +13,6 @@
 
 #include <vector>
 #include <map>
-#include <deque>
 #include <list>
 #include <set>
 #include <functional>
@@ -226,7 +225,7 @@ private:
     uint64_t min_used_journal_sector, max_used_journal_sector;
 
     // Sync
-    std::deque<obj_ver_id> sync_big_writes, sync_small_writes;
+    std::vector<obj_ver_id> sync_big_writes, sync_small_writes;
     std::list<blockstore_operation*>::iterator in_progress_ptr;
     int sync_state, prev_sync_count;
 };
@@ -241,7 +240,7 @@ class blockstore
     spp::sparse_hash_map<object_id, clean_entry, oid_hash> clean_db;
     std::map<obj_ver_id, dirty_entry> dirty_db;
     std::list<blockstore_operation*> submit_queue;
-    std::deque<obj_ver_id> unsynced_big_writes, unsynced_small_writes;
+    std::vector<obj_ver_id> unsynced_big_writes, unsynced_small_writes;
     std::list<blockstore_operation*> in_progress_syncs;
     uint32_t block_order, block_size;
     uint64_t block_count;
diff --git a/blockstore_stable.cpp b/blockstore_stable.cpp
index 892e7392..db2b9ec1 100644
--- a/blockstore_stable.cpp
+++ b/blockstore_stable.cpp
@@ -124,6 +124,7 @@ void blockstore::handle_stable_event(ring_data_t *data, blockstore_operation *op
     {
         // First step: mark dirty_db entries as stable, acknowledge op completion
         // FIXME: oops... we seem to have to copy object id/version pairs...
+        // No, no, no, copying is bad. We don't want copying.
         obj_ver_id* v;
         int i;
         for (i = 0, v = (obj_ver_id*)op->buf; i < op->len; i++, v++)
diff --git a/test.cpp b/test.cpp
index 66737567..3906c496 100644
--- a/test.cpp
+++ b/test.cpp
@@ -14,6 +14,11 @@
 #include <liburing.h>
 
 #include <map>
+#include <vector>
+#include <deque>
+
+#include "blockstore.h"
+#include "cpp-btree/btree_map.h"
 
 static int setup_context(unsigned entries, struct io_uring *ring)
 {
@@ -47,7 +52,76 @@ static void test_write(struct io_uring *ring, int fd)
     free(buf);
 }
 
+class obj_ver_hash
+{
+public:
+    size_t operator()(const obj_ver_id &s) const
+    {
+        size_t seed = 0;
+        spp::hash_combine(seed, s.oid.inode);
+        spp::hash_combine(seed, s.oid.stripe);
+        spp::hash_combine(seed, s.version);
+        return seed;
+    }
+};
+
+inline bool operator == (const obj_ver_id & a, const obj_ver_id & b)
+{
+    return a.oid == b.oid && a.version == b.version;
+}
+
 int main(int argc, char *argv[])
+{
+    // std::map 5M entries -> 2.115s
+    // btree_map 5M entries -> 0.458s
+    // sparse_hash_map 5M entries -> 2.193s
+    //btree::btree_map<obj_ver_id, dirty_entry> dirty_db;
+    //std::map<obj_ver_id, dirty_entry> dirty_db;
+    spp::sparse_hash_map<obj_ver_id, dirty_entry, obj_ver_hash> dirty_db;
+    for (int i = 0; i < 5000000; i++)
+    {
+        dirty_db[(obj_ver_id){
+            .oid = (object_id){
+                .inode = 1,
+                .stripe = i,
+            },
+            .version = 1,
+        }] = (dirty_entry){
+            .state = ST_D_META_SYNCED,
+            .flags = 0,
+            .location = i << 17,
+            .offset = 0,
+            .size = 1 << 17,
+        };
+    }
+    return 0;
+}
+
+int main1(int argc, char *argv[])
+{
+    std::vector<uint64_t> v1, v2;
+    v1.reserve(10000);
+    v2.reserve(10000);
+    for (int i = 0; i < 10000; i++)
+    {
+        v1.push_back(i);
+        v2.push_back(i);
+    }
+    for (int i = 0; i < 100000; i++)
+    {
+        // haha (core i5-2500 | i7-6800HQ)
+        // vector 10000 items: 4.37/100000 | 3.66
+        // vector 100000 items: 9.68/10000 | 0.95
+        // deque 10000 items: 28.432/100000
+        // list 10000 items: 320.695/100000
+        std::vector<uint64_t> v3;
+        v3.insert(v3.end(), v1.begin(), v1.end());
+        v3.insert(v3.end(), v2.begin(), v2.end());
+    }
+    return 0;
+}
+
+int main2(int argc, char *argv[])
 {
     std::map<int, std::string> strs;
     strs.emplace(12, "str");