[l0 v2] Add optional-returning USM pool config parser (#20350)

This PR contains 2 commits, first is just simplification of existing
code, second is a rework to resolve TODO and provide the std::optional
as a return value.

Author: KFilipek

unified-runtime/source/adapters/level_zero/usm.cpp

@@ -45,23 +45,23 @@ usm::DisjointPoolAllConfigs DisjointPoolConfigInstance =
     InitializeDisjointPoolConfig();
 
 usm::DisjointPoolAllConfigs InitializeDisjointPoolConfig() {
-  const char *PoolUrTraceVal = std::getenv("UR_L0_USM_ALLOCATOR_TRACE");
-  const char *PoolPiTraceVal =
-      std::getenv("SYCL_PI_LEVEL_ZERO_USM_ALLOCATOR_TRACE");
-  const char *PoolTraceVal = PoolUrTraceVal
-                                 ? PoolUrTraceVal
-                                 : (PoolPiTraceVal ? PoolPiTraceVal : nullptr);
+  // Prefer the UR-specific env var, fall back to the PI-specific one.
+  const char *PoolTraceVal = std::getenv("UR_L0_USM_ALLOCATOR_TRACE");
+  if (!PoolTraceVal) {
+    PoolTraceVal = std::getenv("SYCL_PI_LEVEL_ZERO_USM_ALLOCATOR_TRACE");
+  }
 
+  // Parse integer value, defaulting to 0 on missing/invalid input.
   int PoolTrace = 0;
-  if (PoolTraceVal != nullptr) {
+  if (PoolTraceVal) {
     PoolTrace = std::atoi(PoolTraceVal);
   }
 
-  const char *PoolUrConfigVal = std::getenv("SYCL_PI_LEVEL_ZERO_USM_ALLOCATOR");
-  const char *PoolPiConfigVal = std::getenv("UR_L0_USM_ALLOCATOR");
-  const char *PoolConfigVal =
-      PoolUrConfigVal ? PoolUrConfigVal : PoolPiConfigVal;
-  if (PoolConfigVal == nullptr) {
+  const char *PoolConfigVal = std::getenv("UR_L0_USM_ALLOCATOR");
+  if (!PoolConfigVal) {
+    PoolConfigVal = std::getenv("SYCL_PI_LEVEL_ZERO_USM_ALLOCATOR");
+  }
+  if (!PoolConfigVal) {
     return usm::DisjointPoolAllConfigs(PoolTrace);
   }
 

unified-runtime/source/adapters/level_zero/usm.hpp

@@ -9,8 +9,6 @@
 //===----------------------------------------------------------------------===//
 #pragma once
 
-#include <set>
-
 #include "common.hpp"
 #include "common/ur_ref_count.hpp"
 #include "enqueued_pool.hpp"

unified-runtime/source/adapters/level_zero/v2/usm.cpp

@@ -43,19 +43,13 @@ ur_result_t getProviderNativeError(const char *providerName,
 
 static std::optional<usm::DisjointPoolAllConfigs>
 initializeDisjointPoolConfig() {
-  const char *UrRetDisable = std::getenv("UR_L0_DISABLE_USM_ALLOCATOR");
-  const char *PiRetDisable =
-      std::getenv("SYCL_PI_LEVEL_ZERO_DISABLE_USM_ALLOCATOR");
-  const char *Disable =
-      UrRetDisable ? UrRetDisable : (PiRetDisable ? PiRetDisable : nullptr);
-  if (Disable != nullptr && Disable != std::string("")) {
+  if (getenv_tobool("UR_L0_DISABLE_USM_ALLOCATOR") ||
+      getenv_tobool("SYCL_PI_LEVEL_ZERO_DISABLE_USM_ALLOCATOR")) {
     return std::nullopt;
   }
 
-  const char *PoolUrTraceVal = std::getenv("UR_L0_USM_ALLOCATOR_TRACE");
-
   int PoolTrace = 0;
-  if (PoolUrTraceVal != nullptr) {
+  if (auto PoolUrTraceVal = std::getenv("UR_L0_USM_ALLOCATOR_TRACE")) {
     PoolTrace = std::atoi(PoolUrTraceVal);
   }
 
@@ -64,14 +58,7 @@ initializeDisjointPoolConfig() {
     return usm::DisjointPoolAllConfigs(PoolTrace);
   }
 
-  // TODO: rework parseDisjointPoolConfig to return optional,
-  // once EnableBuffers is no longer used (by legacy L0)
-  auto configs = usm::parseDisjointPoolConfig(PoolUrConfigVal, PoolTrace);
-  if (configs.EnableBuffers) {
-    return configs;
-  }
-
-  return std::nullopt;
+  return usm::parseDisjointPoolConfigOptional(PoolUrConfigVal, PoolTrace);
 }
 
 inline umf_usm_memory_type_t urToUmfMemoryType(ur_usm_type_t type) {

unified-runtime/source/common/umf_pools/disjoint_pool_config_parser.cpp

@@ -267,4 +267,13 @@ DisjointPoolAllConfigs parseDisjointPoolConfig(const std::string &config,
 
   return AllConfigs;
 }
+
+std::optional<DisjointPoolAllConfigs>
+parseDisjointPoolConfigOptional(const std::string &config, int trace) {
+  auto configs = parseDisjointPoolConfig(config, trace);
+  if (configs.EnableBuffers == 0) {
+    return std::nullopt;
+  }
+  return configs;
+}
 } // namespace usm

unified-runtime/source/common/umf_pools/disjoint_pool_config_parser.hpp

@@ -12,6 +12,7 @@
 #include <umf/pools/pool_disjoint.h>
 
 #include <memory>
+#include <optional>
 #include <string>
 #include <unordered_map>
 
@@ -71,6 +72,13 @@ class DisjointPoolAllConfigs {
 DisjointPoolAllConfigs parseDisjointPoolConfig(const std::string &config,
                                                int trace = 1);
 
+// Parse optional config parameters with optional return.
+// Returns std::nullopt when EnableBuffers is 0, indicating pooling is disabled.
+// This is for use cases where EnableBuffers flag controls pool creation,
+// particularly in the v2 Level Zero adapter.
+std::optional<DisjointPoolAllConfigs>
+parseDisjointPoolConfigOptional(const std::string &config, int trace = 1);
+
 static inline void UMF_CALL_THROWS(umf_result_t res) {
   if (res != UMF_RESULT_SUCCESS) {
     throw res;