Changes on the maps counts again

src/common/memory_detect.cpp

@@ -22,7 +22,6 @@
 
 #include <cstdio>
 #include <cstdlib>
-#include <cstring>
 
 #include "common/memory_detect.h"
 
@@ -76,55 +75,26 @@ const MemoryInfo& GetMemInfo() {
     return mem_info;
 }
 
-u64 GetAvailablePhysicalMemory() {
-#ifdef _WIN32
-    MEMORYSTATUSEX memorystatus;
-    memorystatus.dwLength = sizeof(memorystatus);
-    if (GlobalMemoryStatusEx(&memorystatus)) {
-        return memorystatus.ullAvailPhys;
-    }
-    return 0;
-#elif defined(__linux__)
-    if (std::FILE* const file = std::fopen("/proc/meminfo", "re")) {
-        char line[256];
-        u64 available = 0;
-        while (std::fgets(line, sizeof(line), file) != nullptr) {
-            if (std::strncmp(line, "MemAvailable:", 13) == 0) {
-                available = std::strtoull(line + 13, nullptr, 10) * 1024ULL;
-                break;
-            }
-        }
-        std::fclose(file);
-        if (available != 0) {
-            return available;
-        }
-    }
-    struct sysinfo info;
-    if (sysinfo(&info) == 0) {
-        const u64 unit = info.mem_unit != 0 ? info.mem_unit : 1ULL;
-        return (static_cast<u64>(info.freeram) + static_cast<u64>(info.bufferram)) * unit;
-    }
-    return 0;
-#else
-    return 0;
-#endif
-}
-
-u64 GetMaxMapCount() {
+u64 GetPermissibleMapCount() {
+    constexpr u64 DefaultMapCount = 65530;
+    constexpr u64 ReservedMaps = 20000;
+    u64 count = DefaultMapCount;
 #ifdef __linux__
     if (std::FILE* const file = std::fopen("/proc/sys/vm/max_map_count", "re")) {
         char line[32];
-        u64 count = 0;
         if (std::fgets(line, sizeof(line), file) != nullptr) {
-            count = std::strtoull(line, nullptr, 10);
+            const u64 parsed = std::strtoull(line, nullptr, 10);
+            if (parsed != 0) {
+                count = parsed;
+            }
         }
         std::fclose(file);
-        return count;
     }
-    return 0;
-#else
-    return 0;
 #endif
+    if (count <= ReservedMaps) {
+        return 0;
+    }
+    return count - ReservedMaps;
 }
 
 } // namespace Common