An open's writes in a row to one place go in as one edit: a 10 MB body write is linear

Each body or data write copied and hashed the whole buffer, so a write the mount cut in 8 KB pieces was quadratic: 10 MB took 50 s and a 1 MB insert into 10 MB 11 s, holding the editor's turn. An open's appends to body, or inserts going on at data's address, are now held and put in as one splice (one copy, one undo step, one line-starts pass) before any other request, the close, or the editor's step once the writes pause 20 ms. fs.py-driven: 2 MB 2.19 -> 0.16 s, 10 MB 50.17 -> 0.78 s, 1 MB data into 10 MB 11.49 -> 0.26 s. A body-2m case (2 MB in 256 KB writes on one open) joins the perf gate: 84023 -> 15785 us; baselines re-recorded.

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

4 files changed, 23 insertions, 3 deletions

diff --git a/test/perf-baseline-gui-Debug.json b/test/perf-baseline-gui-Debug.json
index 6bfe2c90..659e49d1 100644
--- a/test/perf-baseline-gui-Debug.json
+++ b/test/perf-baseline-gui-Debug.json
@@ -1 +1 @@
-{"harness":"67f85bf9692f1778","build":{"compiler":"0.16.0","target":"x86_64-linux.5.10...6.19-gnu.2.38","cpu":"x86_64","driver_optimize":"ReleaseFast","core_optimize":"Debug","c_optimize":"ReleaseFast","terminal_optimize":"ReleaseSafe","platform":"gui","grammars":"full","mupdf":true,"jpx":true,"tracy":false,"quic":false,"theme_animation":true,"terminal_simd":true,"prebuilt_shaders":false},"cols":120,"rows":40,"reps":10,"only":"medium","fixtures":[{"name":"small","lines":1000,"cols":60,"bytes":62694},{"name":"medium","lines":50000,"cols":60,"bytes":3201944},{"name":"large","lines":300000,"cols":60,"bytes":19464444},{"name":"longline","lines":400,"cols":8000,"bytes":3200400},{"name":"esp32p4","lines":12,"cols":240,"bytes":2892}],"cells":[{"op":"open","fixture":"medium","min_us":1887,"med_us":2147,"p90_us":2277,"max_us":2326},{"op":"render","fixture":"medium","min_us":73,"med_us":76,"p90_us":84,"max_us":96},{"op":"key-down","fixture":"medium","min_us":73,"med_us":81,"p90_us":84,"max_us":86},{"op":"key-right","fixture":"medium","min_us":73,"med_us":77,"p90_us":91,"max_us":173},{"op":"page-down","fixture":"medium","min_us":75,"med_us":78,"p90_us":80,"max_us":84},{"op":"wheel","fixture":"medium","min_us":72,"med_us":76,"p90_us":79,"max_us":83},{"op":"edit-char","fixture":"medium","min_us":1269,"med_us":1437,"p90_us":1680,"max_us":1697}]}
+{"harness":"b96624a78789195f","build":{"compiler":"0.16.0","target":"x86_64-linux.5.10...6.19-gnu.2.38","cpu":"x86_64","driver_optimize":"ReleaseFast","core_optimize":"Debug","c_optimize":"ReleaseFast","terminal_optimize":"ReleaseSafe","platform":"gui","grammars":"full","mupdf":true,"jpx":true,"tracy":false,"quic":false,"theme_animation":true,"terminal_simd":true,"prebuilt_shaders":false},"cols":120,"rows":40,"reps":10,"only":"medium","fixtures":[{"name":"small","lines":1000,"cols":60,"bytes":62694},{"name":"medium","lines":50000,"cols":60,"bytes":3201944},{"name":"large","lines":300000,"cols":60,"bytes":19464444},{"name":"longline","lines":400,"cols":8000,"bytes":3200400},{"name":"esp32p4","lines":12,"cols":240,"bytes":2892}],"cells":[{"op":"open","fixture":"medium","min_us":1841,"med_us":2197,"p90_us":2308,"max_us":2328},{"op":"render","fixture":"medium","min_us":72,"med_us":81,"p90_us":84,"max_us":86},{"op":"key-down","fixture":"medium","min_us":74,"med_us":74,"p90_us":80,"max_us":81},{"op":"key-right","fixture":"medium","min_us":74,"med_us":80,"p90_us":85,"max_us":100},{"op":"page-down","fixture":"medium","min_us":74,"med_us":81,"p90_us":84,"max_us":176},{"op":"wheel","fixture":"medium","min_us":71,"med_us":75,"p90_us":79,"max_us":93},{"op":"edit-char","fixture":"medium","min_us":1086,"med_us":1515,"p90_us":1692,"max_us":1822},{"op":"body-2m","fixture":"medium","min_us":9044,"med_us":16111,"p90_us":19782,"max_us":21405}]}
diff --git a/test/perf-baseline-tty-Debug.json b/test/perf-baseline-tty-Debug.json
index 6ffd034c..bed59c8c 100644
--- a/test/perf-baseline-tty-Debug.json
+++ b/test/perf-baseline-tty-Debug.json
@@ -1 +1 @@
-{"harness":"67f85bf9692f1778","build":{"compiler":"0.16.0","target":"x86_64-linux.5.10...6.19-gnu.2.38","cpu":"x86_64","driver_optimize":"ReleaseFast","core_optimize":"Debug","c_optimize":"ReleaseFast","terminal_optimize":"ReleaseSafe","platform":"tty","grammars":"full","mupdf":true,"jpx":true,"tracy":false,"quic":false,"theme_animation":true,"terminal_simd":true,"prebuilt_shaders":false},"cols":120,"rows":40,"reps":10,"only":"medium","fixtures":[{"name":"small","lines":1000,"cols":60,"bytes":62694},{"name":"medium","lines":50000,"cols":60,"bytes":3201944},{"name":"large","lines":300000,"cols":60,"bytes":19464444},{"name":"longline","lines":400,"cols":8000,"bytes":3200400},{"name":"esp32p4","lines":12,"cols":240,"bytes":2892}],"cells":[{"op":"open","fixture":"medium","min_us":1907,"med_us":2037,"p90_us":2283,"max_us":2371},{"op":"render","fixture":"medium","min_us":72,"med_us":80,"p90_us":87,"max_us":87},{"op":"key-down","fixture":"medium","min_us":73,"med_us":78,"p90_us":82,"max_us":88},{"op":"key-right","fixture":"medium","min_us":72,"med_us":75,"p90_us":87,"max_us":87},{"op":"page-down","fixture":"medium","min_us":73,"med_us":81,"p90_us":93,"max_us":94},{"op":"wheel","fixture":"medium","min_us":73,"med_us":75,"p90_us":84,"max_us":88},{"op":"edit-char","fixture":"medium","min_us":1333,"med_us":1712,"p90_us":1956,"max_us":2636}]}
+{"harness":"b96624a78789195f","build":{"compiler":"0.16.0","target":"x86_64-linux.5.10...6.19-gnu.2.38","cpu":"x86_64","driver_optimize":"ReleaseFast","core_optimize":"Debug","c_optimize":"ReleaseFast","terminal_optimize":"ReleaseSafe","platform":"tty","grammars":"full","mupdf":true,"jpx":true,"tracy":false,"quic":false,"theme_animation":true,"terminal_simd":true,"prebuilt_shaders":false},"cols":120,"rows":40,"reps":10,"only":"medium","fixtures":[{"name":"small","lines":1000,"cols":60,"bytes":62694},{"name":"medium","lines":50000,"cols":60,"bytes":3201944},{"name":"large","lines":300000,"cols":60,"bytes":19464444},{"name":"longline","lines":400,"cols":8000,"bytes":3200400},{"name":"esp32p4","lines":12,"cols":240,"bytes":2892}],"cells":[{"op":"open","fixture":"medium","min_us":1800,"med_us":2113,"p90_us":2193,"max_us":2326},{"op":"render","fixture":"medium","min_us":71,"med_us":76,"p90_us":85,"max_us":97},{"op":"key-down","fixture":"medium","min_us":73,"med_us":76,"p90_us":82,"max_us":84},{"op":"key-right","fixture":"medium","min_us":72,"med_us":76,"p90_us":81,"max_us":95},{"op":"page-down","fixture":"medium","min_us":74,"med_us":78,"p90_us":83,"max_us":83},{"op":"wheel","fixture":"medium","min_us":72,"med_us":75,"p90_us":82,"max_us":83},{"op":"edit-char","fixture":"medium","min_us":1027,"med_us":1418,"p90_us":1699,"max_us":1834},{"op":"body-2m","fixture":"medium","min_us":8357,"med_us":17722,"p90_us":20080,"max_us":21699}]}
diff --git a/test/perf-baseline-tty-ReleaseFast.json b/test/perf-baseline-tty-ReleaseFast.json
index 5d68e6b2..d13442a5 100644
--- a/test/perf-baseline-tty-ReleaseFast.json
+++ b/test/perf-baseline-tty-ReleaseFast.json
@@ -1 +1 @@
-{"harness":"67f85bf9692f1778","build":{"compiler":"0.16.0","target":"x86_64-linux.5.10...6.19-gnu.2.38","cpu":"x86_64","driver_optimize":"ReleaseFast","core_optimize":"ReleaseFast","c_optimize":"ReleaseFast","terminal_optimize":"ReleaseFast","platform":"tty","grammars":"full","mupdf":true,"jpx":true,"tracy":false,"quic":false,"theme_animation":true,"terminal_simd":true,"prebuilt_shaders":false},"cols":120,"rows":40,"reps":10,"only":"medium","fixtures":[{"name":"small","lines":1000,"cols":60,"bytes":62694},{"name":"medium","lines":50000,"cols":60,"bytes":3201944},{"name":"large","lines":300000,"cols":60,"bytes":19464444},{"name":"longline","lines":400,"cols":8000,"bytes":3200400},{"name":"esp32p4","lines":12,"cols":240,"bytes":2892}],"cells":[{"op":"open","fixture":"medium","min_us":1771,"med_us":2022,"p90_us":2188,"max_us":2228},{"op":"render","fixture":"medium","min_us":75,"med_us":76,"p90_us":76,"max_us":86},{"op":"key-down","fixture":"medium","min_us":73,"med_us":79,"p90_us":80,"max_us":80},{"op":"key-right","fixture":"medium","min_us":72,"med_us":78,"p90_us":81,"max_us":82},{"op":"page-down","fixture":"medium","min_us":72,"med_us":76,"p90_us":80,"max_us":84},{"op":"wheel","fixture":"medium","min_us":75,"med_us":76,"p90_us":78,"max_us":79},{"op":"edit-char","fixture":"medium","min_us":1106,"med_us":1436,"p90_us":1692,"max_us":1721}]}
+{"harness":"b96624a78789195f","build":{"compiler":"0.16.0","target":"x86_64-linux.5.10...6.19-gnu.2.38","cpu":"x86_64","driver_optimize":"ReleaseFast","core_optimize":"ReleaseFast","c_optimize":"ReleaseFast","terminal_optimize":"ReleaseFast","platform":"tty","grammars":"full","mupdf":true,"jpx":true,"tracy":false,"quic":false,"theme_animation":true,"terminal_simd":true,"prebuilt_shaders":false},"cols":120,"rows":40,"reps":10,"only":"medium","fixtures":[{"name":"small","lines":1000,"cols":60,"bytes":62694},{"name":"medium","lines":50000,"cols":60,"bytes":3201944},{"name":"large","lines":300000,"cols":60,"bytes":19464444},{"name":"longline","lines":400,"cols":8000,"bytes":3200400},{"name":"esp32p4","lines":12,"cols":240,"bytes":2892}],"cells":[{"op":"open","fixture":"medium","min_us":1819,"med_us":2002,"p90_us":2068,"max_us":2122},{"op":"render","fixture":"medium","min_us":71,"med_us":76,"p90_us":88,"max_us":89},{"op":"key-down","fixture":"medium","min_us":73,"med_us":75,"p90_us":76,"max_us":82},{"op":"key-right","fixture":"medium","min_us":73,"med_us":77,"p90_us":86,"max_us":126},{"op":"page-down","fixture":"medium","min_us":71,"med_us":75,"p90_us":81,"max_us":83},{"op":"wheel","fixture":"medium","min_us":71,"med_us":74,"p90_us":76,"max_us":97},{"op":"edit-char","fixture":"medium","min_us":1036,"med_us":1493,"p90_us":1805,"max_us":1967},{"op":"body-2m","fixture":"medium","min_us":8482,"med_us":17227,"p90_us":20296,"max_us":23040}]}
diff --git a/test/perf.zig b/test/perf.zig
index e244091c..c639178f 100644
--- a/test/perf.zig
+++ b/test/perf.zig
@@ -46,6 +46,9 @@ const Op = enum {
     page_down,
     wheel,
     edit_char,
+    /// 2 MB appended to the file through 9P, on one open, in 256 KB
+    /// writes: linear, not a copy of the whole buffer per write.
+    body_write,
 
     fn label(o: Op) []const u8 {
         return switch (o) {
@@ -56,10 +59,25 @@ const Op = enum {
             .page_down => "page-down",
             .wheel => "wheel",
             .edit_char => "edit-char",
+            .body_write => "body-2m",
         };
     }
 };
 
+var body_chunk: [256 * 1024]u8 = @splat('y');
+
+/// The body_write gesture: an open of the pane's body, eight 256 KB writes,
+/// a read (which the held writes go in before), the close.
+fn bodyWrite(core: *pardes.Pardes, serial: u32) void {
+    const Node = pardes.ctlfs.Node;
+    const body = Node.of(serial, .body);
+    for (&body_chunk, 0..) |*c, i| c.* = if (i % 64 == 63) '\n' else 'y';
+    const h = core.serveFs(.{ .tag = 1, .op = .open, .node = body, .omode = 1 }).handle;
+    for (0..8) |_| _ = core.serveFs(.{ .tag = 2, .op = .write, .node = body, .handle = h, .data = &body_chunk });
+    _ = core.serveFs(.{ .tag = 3, .op = .getattr, .node = body, .handle = h });
+    _ = core.serveFs(.{ .tag = 4, .op = .release, .node = body, .handle = h, .opened = true });
+}
+
 const TermFixture = struct {
     name: []const u8,
     kb: usize,
@@ -514,12 +532,14 @@ fn measure(op: Op, fx: Fixture, path: []const u8, expected_bytes: usize, reps: u
             .page_down => core.update(.{ .key = .{ .cp = pardes.Key.page_down } }),
             .wheel => core.update(.{ .mouse = .{ .button = .wheel_down, .kind = .press, .col = wheel_col, .row = wheel_row } }),
             .edit_char => core.update(.{ .key = .{ .cp = 'x', .text = "x" } }),
+            .body_write => bodyWrite(core, pane.serial),
         }
         pump(core);
         _ = try frame(core);
         const dt = nowNs() -| t0;
         switch (op) {
             .open => unreachable,
+            .body_write => if (pane.file.?.content.len != before.len + 8 * body_chunk.len) return error.BodyWriteWasNotAppended,
             .render => if (pane.body.cur_row != before.row or pane.body.cur_col != before.col or pane.file.?.content.len != before.len)
                 return error.RenderChangedDocument,
             .key_down => if (pane.body.cur_row != before.row + 1) return error.DownDidNotMove,