The 9P server offers 64 KiB frames, not 8 KiB

8192 was kept for round 24 because 64 KiB seemed to hang fs-test's restore detached space; that was the batch-wake overflow fixed in kmqtwqsm, which any msize could hit, and fs.py passes at 64 KiB with it. A client asking for more now gets it, so a write up to 64 KiB less 24 is one Twrite, and round 24's no-newline cutoff (write_room, the negotiated msize less 24) follows: fs.py checks a 20000-byte ctl line from a 64 KiB client is taken whole. Each of the 16 connection slots holds its buffers at the larger size.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

2 files changed, 15 insertions, 1 deletions

diff --git a/src/9p.zig b/src/9p.zig
index 5ffe9058..837525cb 100644
--- a/src/9p.zig
+++ b/src/9p.zig
@@ -53,7 +53,7 @@ pub const msize_min = cloud9.fs.msize_min;
 /// The smallest msize a native listener offers (src/9p_io.zig).
 pub const min_msize: u32 = 4096;
 /// What a native listener negotiates.
-pub const msize: u32 = 8192;
+pub const msize: u32 = 65536;
 
 /// The editor's engine: native fid count, native file names, and room to
 /// park a write of any size a frame can carry -- a request that would change
diff --git a/test/fs.py b/test/fs.py
index db10f32d..18563183 100644
--- a/test/fs.py
+++ b/test/fs.py
@@ -953,6 +953,20 @@ def test(binary, quic=False):
             with Client(address, msize=256) as small:
                 assert set(small.list('/os' + str(listing))) == {
                     f'entry-{number:02}' for number in range(24)}
+            # 64 KiB frames: a ctl line with no newline, whole in its one
+            # Twrite, runs with it however long -- the cutoff for a write
+            # that may go on is the frame the client asked for, less 24.
+            with Client(address, msize=65536) as big:
+                assert big.msize == 65536
+                ctl = big.open('/pane/1/ctl', 1)
+                line = b'bogus' + b'x' * 20000
+                try:
+                    big.rpc(118, struct.pack('<IQI', ctl, 0, len(line)) + line)
+                except OSError:
+                    pass  # refused with its write (a line over 1024 bytes), not held
+                else:
+                    raise AssertionError('a whole 20000-byte line waited for a newline')
+                big.close(ctl)
 
             frozen = client.open('/screen')
             before = bytearray(client.read_fid(frozen, count=31))