From 2ac834d7971368a6fc3a759f5bbc830cdd095fb6 Mon Sep 17 00:00:00 2001
From: Yaniv Michael Kaul <yaniv.kaul@scylladb.com>
Date: Wed, 15 Apr 2026 09:29:25 +0300
Subject: [PATCH] pch: remove seastar/http/api_docs.hh from precompiled header
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The api_docs.hh header contains inline method bodies (api_registry::handle)
that call seastar::json::formatter::to_json(), forcing the compiler to
instantiate seastar::json template specializations (json_list_template,
formatter::write, do_with, etc.) in every compilation unit — even files
that never use any HTTP/JSON API types.

Measured ~6s of wasted template instantiation per file × ~620 files =
~3,700s total CPU. Only 2 files outside the PCH include api_docs.hh
directly, so removing it has no impact on code that actually uses these
types.

Wall-clock build time (-j16, Seastar/Abseil cached):
  Before (with loading_cache fix): avg 23m29s
  After:                           avg 23m04s  (-1.8%)
  vs original baseline:            avg 24m01s  (-4.0%)
---
 stdafx.hh | 1 -
 1 file changed, 1 deletion(-)

diff --git a/stdafx.hh b/stdafx.hh
index 49fc8f39a0..93cfd012d2 100644
--- a/stdafx.hh
+++ b/stdafx.hh
@@ -254,7 +254,6 @@
 #include <seastar/coroutine/generator.hh>
 #include <seastar/coroutine/maybe_yield.hh>
 #include <seastar/coroutine/parallel_for_each.hh>
-#include <seastar/http/api_docs.hh>
 #include <seastar/http/client.hh>
 #include <seastar/http/common.hh>
 #include <seastar/http/connection_factory.hh>