diff --git a/src/spall.zig b/src/spall.zig
index ee6270a2e6a4067e41918afe57b48917686147a3..758ae936950c30560797ce69a44a83e145c5ae9b 100644
--- a/src/spall.zig
+++ b/src/spall.zig
@@ -9,6 +9,7 @@ var pid: std.os.linux.pid_t = undefined;
 threadlocal var tid: std.os.linux.pid_t = undefined;
 threadlocal var path: []const u8 = undefined;
 threadlocal var file: std.fs.File = undefined;
+threadlocal var buffered_writer: std.io.BufferedWriter(4096, std.fs.File.Writer) = undefined;
 
 pub fn init() !void {
     pid = std.os.linux.getpid();
@@ -23,19 +24,22 @@ pub fn init2() !void {
 
     path = try std.fmt.allocPrint(alloc, "/data/trace.{d}.{d}.spall.jsonl", .{ pid, tid });
     file = try std.fs.cwd().createFile(path, .{});
-    try file.writer().writeAll("[\n");
+    buffered_writer = std.io.bufferedWriter(file.writer());
+
+    try buffered_writer.writer().writeAll("[\n");
 }
 
 pub fn deinit2() void {
     defer alloc.free(path);
     defer file.close();
 
-    file.writer().writeAll("]\n") catch {};
+    buffered_writer.writer().writeAll("]\n") catch {};
+    buffered_writer.flush() catch {};
     log.debug("{s}", .{path});
 }
 
 pub inline fn trace_begin(ctx: tracer.Ctx) void {
-    file.writer().print(
+    buffered_writer.writer().print(
         \\{{"cat":"function", "name":"{s}:{d}:{d} ({s})", "ph": "B", "pid": {d}, "tid": {d}, "ts": {d}}},
         \\
     ,
@@ -53,7 +57,7 @@ pub inline fn trace_begin(ctx: tracer.Ctx) void {
 
 pub inline fn trace_end(ctx: tracer.Ctx) void {
     _ = ctx;
-    file.writer().print(
+    buffered_writer.writer().print(
         \\{{"cat":"function", "ph": "E", "pid": {d}, "tid": {d}, "ts": {d}}},
         \\
     ,