2 files changed, 43 insertions, 12 deletions
diff --git a/packages/meshbay-node/src/meshbay_node/config.py b/packages/meshbay-node/src/meshbay_node/config.py
index c5596f1..d46ab8c 100644
--- a/packages/meshbay-node/src/meshbay_node/config.py
+++ b/packages/meshbay-node/src/meshbay_node/config.py
@@ -74,13 +74,14 @@ max_concurrent_uploads = 8
 # the partial file is deleted.
 max_upload_gb = 8
 
-# How many processes carry the connections of members. At 1 the node does it
+# How many processes carry the connections of members. Left unset: one per core
+# of this machine, up to four, about 85 MB of memory each. At 1 the node does it
 # all in one process, on one core: about 35 MB/s summed over every transfer in
-# progress. Above 1 the node starts that many processes for the connections and
-# keeps the rest for itself, so transfers use that many cores, plus part of one
-# for the node. Takes effect for new connections, without a restart. Not above
-# the number of cores of this machine.
-connection_processes = 1
+# progress on Linux, and much less on Windows. Above 1 the node starts that many
+# processes for the connections and keeps the rest for itself, so transfers use
+# that many cores, plus part of one for the node. Takes effect for new
+# connections, without a restart. Not above the number of cores of this machine.
+# connection_processes = 4
 
 # HEVC sources have no browser decoder on most platforms, so streaming one is
 # transcoded to H264 rather than the usual free copy — real CPU per viewer.
@@ -202,8 +203,9 @@ class NodeConfig:
     # §15.3), so this is what stands between a writable root and a full disk.
     max_upload_gb: float = 8.0
     # How many processes hold the peer connections. One means this process
-    # holds them itself, as it always did. See transport/webrtc/workers.py.
-    connection_processes: int = 1
+    # holds them itself. See transport/webrtc/workers.py, and
+    # `default_connection_processes` for why it is not one by default.
+    connection_processes: int = field(default_factory=lambda: default_connection_processes())
     # HEVC (and any future codec in media_probe.py's
     # BROWSER_INCOMPATIBLE_VIDEO_CODECS) has no decoder in most browsers, so
     # streaming it needs a real re-encode to H264 rather than the usual free
@@ -305,6 +307,23 @@ def max_processes() -> int:
     return max(1, os.cpu_count() or 1)
 
 
+# Above four, a single download no longer gains (docs/MESHBAY_DESIGN.md §5.5:
+# 131 MB/s at four, 150 at eight with the receiving browser the limit), and each
+# process is 85 MB held for the life of the node.
+DEFAULT_CONNECTION_PROCESSES_MAX = 4
+
+
+def default_connection_processes() -> int:
+    """
+    One per core, up to four. It was 1, which starts no process at all: the
+    several-cores path was measured, shipped and reached by no node whose
+    operator had not found the setting, and the lanes of a download all landed
+    on the node's one core — on Windows, where Python's UDP costs most, a
+    download over eight connections was as slow as over one.
+    """
+    return min(DEFAULT_CONNECTION_PROCESSES_MAX, max_processes())
+
+
 def _positive(value: object, default: int, name: str) -> int:
     """A count that must be at least one, or the default with a word about it.
 
diff --git a/packages/meshbay-node/tests/test_connection_processes.py b/packages/meshbay-node/tests/test_connection_processes.py
index ab9dfd3..778da5a 100644
--- a/packages/meshbay-node/tests/test_connection_processes.py
+++ b/packages/meshbay-node/tests/test_connection_processes.py
@@ -13,6 +13,7 @@ not carry.
 """
 
 import asyncio
+import re
 import struct
 from pathlib import Path
 
@@ -231,11 +232,21 @@ async def test_one_process_starts_none():
 
 # ── the setting ─────────────────────────────────────────────────────────────
 
-def test_the_default_is_one_process(tmp_path):
-    assert node_settings_defaults()["connection_processes"] == 1
+@pytest.mark.parametrize("cores, expected", [(1, 1), (2, 2), (4, 4), (28, 4)])
+def test_the_default_is_one_per_core_up_to_four(tmp_path, monkeypatch, cores, expected):
+    """It was 1, which starts none: the path was shipped and reached by no node
+    whose operator had not found the setting."""
+    monkeypatch.setattr("meshbay_node.config.max_processes", lambda: cores)
+    assert node_settings_defaults()["connection_processes"] == expected
     conf = tmp_path / "node.toml"
     conf.write_text('[hub]\nurl = "https://example.invalid"\nusername = "op"\n')
-    assert load_config(conf).node.connection_processes == 1
+    assert load_config(conf).node.connection_processes == expected
+
+
+def test_a_new_node_toml_leaves_it_to_the_default(tmp_path):
+    from meshbay_node.config import EXAMPLE_CONFIG
+    assert not re.search(r"^connection_processes\s*=", EXAMPLE_CONFIG, re.M), (
+        "a value written by `init` is a value no later default reaches")
 
 
 def test_node_toml_cannot_ask_for_more_than_the_cores(tmp_path):
@@ -296,4 +307,5 @@ async def test_a_number_the_machine_cannot_honour_is_refused(state, monkeypatch,
     with pytest.raises(ops.OpError):
         await ops.set_node_settings(state, {"connection_processes": value})
     assert state["webrtc"].asked == []
-    assert (await ops.get_node_settings(state))["connection_processes"] == 1
+    assert ((await ops.get_node_settings(state))["connection_processes"]
+            == state["config"].node.connection_processes)