diff --git a/src/system/libroot/posix/string/arch/x86_64/arch_string.cpp b/src/system/libroot/posix/string/arch/x86_64/arch_string.cpp
index b83376c331..33fca22474 100644
--- a/src/system/libroot/posix/string/arch/x86_64/arch_string.cpp
+++ b/src/system/libroot/posix/string/arch/x86_64/arch_string.cpp
@@ -5,6 +5,9 @@
 
 
 #include <cstddef>
+#include <cstdint>
+
+#include <x86intrin.h>
 
 
 extern "C" void*
@@ -18,14 +21,77 @@ memcpy(void* destination, const void* source, size_t length)
 }
 
 
-extern "C" void*
-memset(void* destination, int value, size_t length)
+static inline void
+memset_repstos(uint8_t* destination, uint8_t value, size_t length)
 {
-	auto returnValue = destination;
 	__asm__ __volatile__("rep stosb"
 		: "+D" (destination), "+c" (length)
 		: "a" (value)
 		: "memory");
-	return returnValue;
+}
+
+
+static inline void
+memset_sse(uint8_t* destination, uint8_t value, size_t length)
+{
+	__m128i packed = _mm_set1_epi8(value);
+	auto end = reinterpret_cast<__m128i*>(destination + length - 16);
+	auto diff = reinterpret_cast<uintptr_t>(destination) % 16;
+	if (diff) {
+		diff = 16 - diff;
+		length -= diff;
+		_mm_storeu_si128(reinterpret_cast<__m128i*>(destination), packed);
+	}
+	auto ptr = reinterpret_cast<__m128i*>(destination + diff);
+	while (length >= 64) {
+		_mm_store_si128(ptr++, packed);
+		_mm_store_si128(ptr++, packed);
+		_mm_store_si128(ptr++, packed);
+		_mm_store_si128(ptr++, packed);
+		length -= 64;
+	}
+	while (length >= 16) {
+		_mm_store_si128(ptr++, packed);
+		length -= 16;
+	}
+	_mm_storeu_si128(end, packed);
+}
+
+
+static inline void
+memset_small(uint8_t* destination, uint8_t value, size_t length)
+{
+	if (length >= 8) {
+		auto packed = value * 0x101010101010101ul;
+		auto ptr = reinterpret_cast<uint64_t*>(destination);
+		auto end = reinterpret_cast<uint64_t*>(destination + length - 8);
+		while (length >= 8) {
+			*ptr++ = packed;
+			length -= 8;
+		}
+		*end = packed;
+	} else {
+		while (length--) {
+			*destination++ = value;
+		}
+	}
+}
+
+
+extern "C" void*
+memset(void* ptr, int chr, size_t length)
+{
+	auto value = static_cast<unsigned char>(chr);
+	auto destination = static_cast<uint8_t*>(ptr);
+	if (length < 32) {
+		memset_small(destination, value, length);
+		return ptr;
+	}
+	if (length < 2048) {
+		memset_sse(destination, value, length);
+		return ptr;
+	}
+	memset_repstos(destination, value, length);
+	return ptr;
 }