Use exact number of requests when testing warmup

Author: fwsGonzo

lib/libkvm/backend.cpp

@@ -870,8 +870,17 @@ void backend_warmup_pause_resume(MachineInstance& machine,
 			if (!perform_warmup_request(machine, invoc, warmup.headers))
 				break;
 		}
-		/* Check if this was an improvement */
-		if (const auto* profiler = vm.profiling(); profiler != nullptr) {
+		if (warmup.exact) {
+			// Exact number of warmup requests, so just do that many
+			if (i+1 >= warmup.num_requests) {
+				if (machine.tenant().config.group.verbose) {
+					printf("Warmup: Completed %d exact warmup requests\n", warmup.num_requests);
+				}
+				break;
+			}
+		}
+		else if (const auto* profiler = vm.profiling(); profiler != nullptr) {
+			/* Heuristic: Check if this was an improvement */
 			const auto& samples = profiler->times[tinykvm::MachineProfiling::UserDefined];
 			const bool is_improvement = (samples.back() < best_time);
 			if (is_improvement) {

lib/libkvm/ext/tinykvm

@@ -527,6 +527,9 @@ static void configure_group(const std::string& name, kvm::TenantGroup& group, co
 			} else {
 				group.warmup->num_requests = 20;
 			}
+			if (obj2.contains("exact")) {
+				group.warmup->exact = obj2["exact"];
+			}
 			if (obj2.contains("url")) {
 				group.warmup->url = obj2["url"];
 			}

lib/libkvm/tenant.cpp

@@ -48,6 +48,7 @@ struct TenantGroup {
 	/* Warmup the VM before starting 'real' request handling. */
 	struct Warmup {
 		uint16_t num_requests = 0;
+		bool exact = false; /* Use exact number of requests, otherwise heuristic */
 		std::string url = "/";
 		std::string method = "GET";
 		std::unordered_set<std::string> headers {

lib/libkvm/tenant.hpp

@@ -15,7 +15,7 @@ int main(int argc, char **argv)
 	while (1) {
 		wait_for_requests_paused(&req);
 
-		if (counter < 15) {
+		if (IS_WARMUP_REQUEST(&req)) {
 			assert(strcmp(req.url, "/warmup") == 0);
 		} else {
 			assert(strcmp(req.url, "/1") == 0);
@@ -56,6 +56,7 @@ vcl 4.1;
 			"filename": "${tmpdir}/hello",
 			"warmup": {
 				"num_requests": 15,
+				"exact": true,
 				"url": "/warmup",
 				"headers": [
 					"Host: localhost",