Merge bitcoin/bitcoin#31164: net: Use actual memory size in receive b…

…uffer accounting

d22a234 net: Use actual memory size in receive buffer accounting (laanwj)
047b5e2 streams: add DataStream::GetMemoryUsage (laanwj)
c3a6722 net: Use DynamicUsage(m_type) in CSerializedNetMsg::GetMemoryUsage (laanwj)
c6594c0 memusage: Add DynamicUsage for std::string (laanwj)
7596282 memusage: Allow counting usage of vectors with different allocators (laanwj)

Pull request description:

  Add a method `CNetMessage::GetMemoryUsage` and use this for accounting of the size of the process receive queue instead of the raw message size (like we already do for the send buffer and `CSerializedNetMsg`).

  This ensures that allocation and deserialization overhead is better taken into account.

  On average, this counts about ~100 extra bytes per packet on x86_64:
  ```
  2024-10-27T09:50:12Z [net] 24 bytes -> 112 bytes
  2024-10-27T10:36:37Z [net] 61 bytes -> 176 bytes
  2024-10-27T10:36:38Z [net] 1285 bytes -> 1392 bytes
  2024-10-27T09:50:21Z [net] 43057 bytes -> 43168 bytes
  ```

ACKs for top commit:
  l0rinc:
    ACK d22a234
  achow101:
    ACK d22a234
  i-am-yuvi:
    ACK d22a234
  danielabrozzoni:
    Light ACK d22a234 - code looks good to me, but I'm not very familiar with C++ memory management specifics

Tree-SHA512: ef09707e77b67bdbc48e9464133e4fccfa5c05051c1022e81ad84f20ed41db83ac5a9b109ebdb8d38f70785c03c5d6bfe51d32dc133d49e52d1e6225f6f8e292

src/memusage.h

@@ -15,6 +15,7 @@
 #include <map>
 #include <memory>
 #include <set>
+#include <string>
 #include <vector>
 #include <unordered_map>
 #include <unordered_set>
@@ -84,10 +85,22 @@ struct stl_shared_counter
     size_t weak_count;
 };
 
-template<typename X>
-static inline size_t DynamicUsage(const std::vector<X>& v)
+template<typename T, typename Allocator>
+static inline size_t DynamicUsage(const std::vector<T, Allocator>& v)
+{
+    return MallocUsage(v.capacity() * sizeof(T));
+}
+
+static inline size_t DynamicUsage(const std::string& s)
 {
-    return MallocUsage(v.capacity() * sizeof(X));
+    const char* s_ptr = reinterpret_cast<const char*>(&s);
+    // Don't count the dynamic memory used for string, if it resides in the
+    // "small string" optimization area (which stores data inside the object itself, up to some
+    // size; 15 bytes in modern libstdc++).
+    if (!std::less{}(s.data(), s_ptr) && !std::greater{}(s.data() + s.size(), s_ptr + sizeof(s))) {
+        return 0;
+    }
+    return MallocUsage(s.capacity());
 }
 
 template<unsigned int N, typename X, typename S, typename D>

src/net.cpp

@@ -121,10 +121,12 @@ std::string strSubVersion;
 
 size_t CSerializedNetMsg::GetMemoryUsage() const noexcept
 {
-    // Don't count the dynamic memory used for the m_type string, by assuming it fits in the
-    // "small string" optimization area (which stores data inside the object itself, up to some
-    // size; 15 bytes in modern libstdc++).
-    return sizeof(*this) + memusage::DynamicUsage(data);
+    return sizeof(*this) + memusage::DynamicUsage(m_type) + memusage::DynamicUsage(data);
+}
+
+size_t CNetMessage::GetMemoryUsage() const noexcept
+{
+    return sizeof(*this) + memusage::DynamicUsage(m_type) + m_recv.GetMemoryUsage();
 }
 
 void CConnman::AddAddrFetch(const std::string& strDest)
@@ -3772,7 +3774,7 @@ void CNode::MarkReceivedMsgsForProcessing()
     for (const auto& msg : vRecvMsg) {
         // vRecvMsg contains only completed CNetMessage
         // the single possible partially deserialized message are held by TransportDeserializer
-        nSizeAdded += msg.m_raw_message_size;
+        nSizeAdded += msg.GetMemoryUsage();
     }
 
     LOCK(m_msg_process_queue_mutex);
@@ -3789,7 +3791,7 @@ std::optional<std::pair<CNetMessage, bool>> CNode::PollMessage()
     std::list<CNetMessage> msgs;
     // Just take one message
     msgs.splice(msgs.begin(), m_msg_process_queue, m_msg_process_queue.begin());
-    m_msg_process_queue_size -= msgs.front().m_raw_message_size;
+    m_msg_process_queue_size -= msgs.front().GetMemoryUsage();
     fPauseRecv = m_msg_process_queue_size > m_recv_flood_size;
 
     return std::make_pair(std::move(msgs.front()), !m_msg_process_queue.empty());

src/net.h

@@ -245,6 +245,9 @@ class CNetMessage
     CNetMessage(const CNetMessage&) = delete;
     CNetMessage& operator=(CNetMessage&&) = default;
     CNetMessage& operator=(const CNetMessage&) = delete;
+
+    /** Compute total memory usage of this object (own memory + any dynamic memory). */
+    size_t GetMemoryUsage() const noexcept;
 };
 
 /** The Transport converts one connection's sent messages to wire bytes, and received bytes back. */

src/streams.cpp

@@ -2,6 +2,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or https://opensource.org/license/mit/.
 
+#include <memusage.h>
 #include <span.h>
 #include <streams.h>
 #include <util/fs_helpers.h>
@@ -110,3 +111,8 @@ bool AutoFile::Truncate(unsigned size)
 {
     return ::TruncateFile(m_file, size);
 }
+
+size_t DataStream::GetMemoryUsage() const noexcept
+{
+    return sizeof(*this) + memusage::DynamicUsage(vch);
+}

src/streams.h

@@ -277,6 +277,9 @@ class DataStream
     {
         util::Xor(MakeWritableByteSpan(*this), MakeByteSpan(key));
     }
+
+    /** Compute total memory usage of this object (own memory + any dynamic memory). */
+    size_t GetMemoryUsage() const noexcept;
 };
 
 template <typename IStream>