Try to allocate scratchpad from dataset's 1 GB huge pages, if normal huge pages are not available

src/crypto/rx/RxDataset.cpp

@@ -193,6 +193,12 @@ void xmrig::RxDataset::allocate(bool hugePages, bool oneGbPages)
     }
 
     m_memory  = new VirtualMemory(maxSize(), hugePages, oneGbPages, false, m_node);
+
+    if (m_memory->isOneGbPages()) {
+        m_scratchpadOffset = maxSize() + RANDOMX_CACHE_MAX_SIZE;
+        m_scratchpadLimit = m_memory->capacity();
+    }
+
     m_dataset = randomx_create_dataset(m_memory->raw());
 
 #   ifdef XMRIG_OS_LINUX
@@ -201,3 +207,19 @@ void xmrig::RxDataset::allocate(bool hugePages, bool oneGbPages)
     }
 #   endif
 }
+
+
+uint8_t* xmrig::RxDataset::tryAllocateScrathpad()
+{
+    uint8_t* p = reinterpret_cast<uint8_t*>(raw());
+    if (!p) {
+        return nullptr;
+    }
+
+    const size_t offset = m_scratchpadOffset.fetch_add(RANDOMX_SCRATCHPAD_L3_MAX_SIZE);
+    if (offset + RANDOMX_SCRATCHPAD_L3_MAX_SIZE > m_scratchpadLimit) {
+        return nullptr;
+    }
+
+    return p + offset;
+}

src/crypto/rx/RxDataset.h

@@ -36,6 +36,8 @@
 #include "crypto/randomx/randomx.h"
 #include "crypto/rx/RxConfig.h"
 
+#include <atomic>
+
 
 struct randomx_dataset;
 
@@ -69,6 +71,8 @@ public:
     void *raw() const;
     void setRaw(const void *raw);
 
+    uint8_t *tryAllocateScrathpad();
+
     static inline constexpr size_t maxSize() { return RANDOMX_DATASET_MAX_SIZE; }
 
 private:
@@ -79,6 +83,9 @@ private:
     randomx_dataset *m_dataset  = nullptr;
     RxCache *m_cache            = nullptr;
     VirtualMemory *m_memory     = nullptr;
+
+    std::atomic<size_t> m_scratchpadOffset;
+    size_t m_scratchpadLimit    = 0;
 };