Memoize read-only source graph stats

src/lib/compiler.cpp

@@ -3,6 +3,7 @@
 #include "hash.h"
 #include <algorithm>
 #include <cerrno>
+#include <chrono>
 #include <cstdlib>
 #include <cctype>
 #include <cstring>
@@ -50,6 +51,7 @@ struct SharedUnitCompileCheck
 
 struct UnitSourceSignatureEntry
 {
+	std::chrono::steady_clock::time_point checked_at;
 	u64 modified_ns = 0;
 	u64 changed_ns = 0;
 	u64 size = 0;
@@ -144,12 +146,22 @@ bool compiler_source_readable(String file_name, const struct stat& info, int* re
 	return(error == 0);
 }
 
-UnitSourceSignatureEntry compiler_unit_source_entry(String file_name)
+UnitSourceSignatureEntry compiler_unit_source_entry(String file_name, bool allow_recent_stat)
 {
+	auto checked_at = std::chrono::steady_clock::now();
+	if(allow_recent_stat)
+	{
+		std::lock_guard<std::mutex> lock(unit_source_signature_cache_mutex);
+		auto cached = unit_source_signature_cache.find(file_name);
+		if(cached != unit_source_signature_cache.end() &&
+			std::chrono::duration_cast<std::chrono::milliseconds>(checked_at - cached->second.checked_at).count() < 1000)
+			return(cached->second);
+	}
 	struct stat info;
 	UnitSourceSignatureEntry entry;
 	if(stat(file_name.c_str(), &info) != 0)
 		return(entry);
+	entry.checked_at = checked_at;
 	entry.modified_ns = (u64)info.st_mtim.tv_sec * 1000000000ull + (u64)info.st_mtim.tv_nsec;
 	entry.changed_ns = (u64)info.st_ctim.tv_sec * 1000000000ull + (u64)info.st_ctim.tv_nsec;
 	entry.size = (u64)info.st_size;
@@ -158,7 +170,10 @@ UnitSourceSignatureEntry compiler_unit_source_entry(String file_name)
 		std::lock_guard<std::mutex> lock(unit_source_signature_cache_mutex);
 		auto cached = unit_source_signature_cache.find(file_name);
 		if(cached != unit_source_signature_cache.end() && cached->second.modified_ns == entry.modified_ns && cached->second.changed_ns == entry.changed_ns && cached->second.size == entry.size && cached->second.readable == entry.readable)
+		{
+			cached->second.checked_at = checked_at;
 			return(cached->second);
+		}
 	}
 	String content = file_get_contents(file_name);
 	entry.content_hash = gen_sha1(content);
@@ -172,7 +187,7 @@ UnitSourceSignatureEntry compiler_unit_source_entry(String file_name)
 	return(entry);
 }
 
-void compiler_append_unit_source_signature(String file_name, std::set<String>& visited, String& signature)
+void compiler_append_unit_source_signature(String file_name, std::set<String>& visited, String& signature, bool allow_recent_stat)
 {
 	String normalized = path_real(file_name);
 	if(normalized == "")
@@ -181,28 +196,28 @@ void compiler_append_unit_source_signature(String file_name, std::set<String>& v
 		return;
 	visited.insert(normalized);
 
-	UnitSourceSignatureEntry entry = compiler_unit_source_entry(normalized);
+	UnitSourceSignatureEntry entry = compiler_unit_source_entry(normalized, allow_recent_stat);
 	signature += normalized + ":" + entry.content_hash + (entry.readable ? String("") : String(":unreadable")) + "\n";
 	for(String loaded : entry.loaded_paths)
-		compiler_append_unit_source_signature(loaded, visited, signature);
+		compiler_append_unit_source_signature(loaded, visited, signature, allow_recent_stat);
 }
 
-String compiler_unit_source_signature(String file_name)
+String compiler_unit_source_signature(String file_name, bool allow_recent_stat = false)
 {
 	std::set<String> visited;
 	String signature = "uce-load-graph-v1\n";
-	compiler_append_unit_source_signature(file_name, visited, signature);
+	compiler_append_unit_source_signature(file_name, visited, signature, allow_recent_stat);
 	return(gen_sha1(signature));
 }
 
-String compiler_unit_input_signature(Request* context, SharedUnit* su)
+String compiler_unit_input_signature(Request* context, SharedUnit* su, bool allow_recent_source_stat = false)
 {
 	if(!context || !su || !file_exists(su->file_name))
 		return("");
 
 	String setup_template = context->server->config["COMPILER_SYS_PATH"] + "/" + context->server->config["SETUP_TEMPLATE"];
 	return(
-		compiler_unit_source_signature(su->file_name) + ":" +
+		compiler_unit_source_signature(su->file_name, allow_recent_source_stat) + ":" +
 		gen_sha1(file_get_contents(setup_template)) + ":" +
 		std::to_string(UCE_UNIT_ABI_VERSION)
 	);
@@ -452,7 +467,7 @@ bool compiler_has_known_unit_cached(Request* context, String file_name)
 	}));
 }
 
-SharedUnitFilesystemState inspect_shared_unit_filesystem(Request* context, SharedUnit* su)
+SharedUnitFilesystemState inspect_shared_unit_filesystem(Request* context, SharedUnit* su, bool allow_recent_source_stat = false)
 {
 	SharedUnitFilesystemState state;
 	state.source_exists = file_exists(su->file_name);
@@ -465,7 +480,7 @@ SharedUnitFilesystemState inspect_shared_unit_filesystem(Request* context, Share
 	state.compiler_abi_time = compiler_runtime_abi_time(context);
 	state.metadata_time = file_mtime(su->meta_file_name);
 	state.compile_output_time = file_mtime(su->compile_output_file_name);
-	state.current_input_signature = compiler_unit_input_signature(context, su);
+	state.current_input_signature = compiler_unit_input_signature(context, su, allow_recent_source_stat);
 	state.metadata_exists = (state.metadata_time != 0);
 	state.compile_output_exists = (state.compile_output_time != 0);
 	if(state.metadata_exists)
@@ -1301,12 +1316,12 @@ void compiler_untrack_known_unit(Request* context, String file_name)
 	});
 }
 
-bool compiler_unit_needs_recompile(Request* context, String file_name, bool* source_missing)
+bool compiler_unit_needs_recompile(Request* context, String file_name, bool* source_missing, bool allow_recent_source_stat)
 {
 	file_name = compiler_normalize_unit_path(context, file_name);
 	SharedUnit su;
 	setup_unit_paths(context, &su, file_name);
-	auto state = inspect_shared_unit_filesystem(context, &su);
+	auto state = inspect_shared_unit_filesystem(context, &su, allow_recent_source_stat);
 	auto compile_check = shared_unit_compile_check(state);
 	if(source_missing)
 		*source_missing = compile_check.source_missing;

src/lib/compiler.h

@@ -27,7 +27,7 @@ StringList compiler_list_known_units(Request* context);
 void compiler_set_known_units(Request* context, StringList files);
 void compiler_track_known_unit(Request* context, String file_name);
 void compiler_untrack_known_unit(Request* context, String file_name);
-bool compiler_unit_needs_recompile(Request* context, String file_name, bool* source_missing = 0);
+bool compiler_unit_needs_recompile(Request* context, String file_name, bool* source_missing = 0, bool allow_recent_source_stat = false);
 DValue unit_info(String path = "");
 StringList units_list();
 bool unit_compile(String path = "");

src/wasm/worker.cpp

@@ -2210,7 +2210,7 @@ private:
 					now - cached_freshness->second.checked_at).count() >= 1000;
 			if(check_freshness)
 			{
-				stale = compiler_unit_needs_recompile(context, resolved, 0);
+				stale = compiler_unit_needs_recompile(context, resolved, 0, can_serve_stale && read_request);
 				worker.component_freshness[resolved] = { now, stale };
 			}
 			else