dathskovsky@speedata.io | www.linkedin.com/in/alexdathskovsky • what will the result be if we call add_uint8(255u, 1u)?SURPRISE AGAIN: INTEGER PROMOTION Alex Dathskovsky | alex.dathskovsky@speedata.io | www dathskovsky@speedata.io | www.linkedin.com/in/alexdathskovsky • what will be the result if we will call add_uint8(255u, 1u) ?INTEGER NARROWING Alex Dathskovsky | alex.dathskovsky@speedata.io | www.linkedin.com/in/alexdathskovsky dathskovsky@speedata.io | www.linkedin.com/in/alexdathskovsky • what will be the result if we will call my_add(uint64_t(1), int64_t(-2)) ?SURPRISE AGAIN: MORE INTEGER PROMOTION Alex Dathskovsky | alex.dathskovsky@speedata

is protected by a mutex. var ( countLock sync.Mutex inputCount uint32 outputCount uint32 errorCount uint32 ) Names Names are as important in Go as in any other language. In some size; instead, the printing routines use the type of the argument to decide these properties. var x uint64 = 1<<64 - 1 fmt.Printf("%d %x; %d %x\n", x, x, int64(x), int64(x)) prints 18446744073709551615 min function that chooses the least of a list of integers: func Min(a ...int) int { min := int(^uint(0) >> 1) // largest int for _, i := range a { if i < min { min = i

constexpr uint64_t CPU_CLOCK_HZ = 400'000'000; // API to implement: std::chrono::nanoseconds elapsed_time(uint64_t num_cpu_ticks); 1 2 3 4 8Example: “CPU ticks” time units constexpr uint64_t CPU_CLOCK_HZ // API to implement: std::chrono::nanoseconds elapsed_time(uint64_t num_cpu_ticks); 1 2 3 4 std::chrono::nanoseconds elapsed_time(uint64_t num_cpu_ticks) { using NS_PER_TICK = std::ratio<1'000'000'000 units constexpr uint64_t CPU_CLOCK_HZ = 400'000'000; // API to implement: std::chrono::nanoseconds elapsed_time(uint64_t num_cpu_ticks); 1 2 3 4 std::chrono::nanoseconds elapsed_time(uint64_t num_cpu_ticks)

operations may get fusedCode density uint64_t v = 0x123456789abcdef0; 46 x86 movabs r10, 0x123456789abcdef0 49 ba f0 de bc 9a 78 56 34 12Code density uint64_t v = 0x123456789abcdef0; 47 x86 movabs $2, 0xdef0 46 02 02 3c cf 8a 42 34 78 14 02 00 af 26 42 64 b8 14 02 00 f0 de 42 34Code density uint64_t v = 0x123456789abcdef0; 48 x86 movabs r10, 0x123456789abcdef0 49 ba f0 de bc 9a 78 56 34 12 $2, 0xdef0 46 02 02 3c cf 8a 42 34 78 14 02 00 af 26 42 64 b8 14 02 00 f0 de 42 34Code density uint64_t v = 0x123456789abcdef0; 49 x86 movabs r10, 0x123456789abcdef0 49 ba f0 de bc 9a 78 56 34 12

UNKNOWN_ERROR = 1; // NOSPACE = 2; // } // fs interface message GetFsInfoRequest { optional uint32 fsId = 1; // fs id optional string fsName = 2; // fs name } message mountPoint { host = 1; required string mountDir = 2; // } message Volume { required uint64 volumeSize = 1; required uint64 blockSize = 2; required string volumeName = 3; required string user = FsInfo { required uint32 fsId = 1;© XXX Page 4 of 15 required string fsName = 2; required uint64 rootInodeId = 3; required uint64 capacity = 4; required uint64 blockSize = 5; required

⚫ data: 0 bytes ⚫ bss: 1568 bytes 6Traditional HAL void GPIO_Init(GPIO_InitStruct* conf) { uint32_t temp; /* check the values */ if (!IS_GPIO_PIN(conf->pin)) { return; } if (!IS_GPIO_MODE(conf->mode)) (conf->pin * 2u)); OSPEEDR = temp; /* ... */ } /* ... */ } 7 typedef struct { uint32_t pin; GPIO_Modes mode; } GPIO_InitStruct; int main (void) { GPIO_InitStruct conf = { 0 const std::uint32_t m_address; public: CRegister (std::uint32_t address) : m_address(address) { } void set (std::uint32_t val) const { *(reinterpret_castuint32_t *>(m_address))

案主要针对的场景是顺序写和顺序 读，而对于随机写和随机读来说也会有一定性能提升，但效果可能不会太好。 元数据采用2层索引 由于chunk大小是固定的（默认64M），所以Inode中采用map<uint64, S3ChunkInfoList> s3ChunkInfoMap用于保存对象存储的位置信息。采用2级索引的好处是，根据操作的offset可以快速定位到index，则只需要遍历index相关的 S3ChunkInfo { required uint64 chunkId = 1; required uint64 compaction = 2; required uint64 offset = 3; required uint64 len = 4; // file logic length required uint64 size = 5; // file size required uint64 inodeId = 1; required uint32 fsId = 2; required uint64 length = 3; required uint32 ctime = 4; required uint32 mtime = 5; required uint32 atime = 6; required uint32 uid

true. Otherwise return false. // Precondition: The counter is not zero bool decrement(); uint64_t read(); // Return the current value of the counter }; • Sometimes referred to as a “sticky counter” } bool decrement() { return (--counter == 0); } uint64_t read() { return counter; } uint64_t counter{1}; }; Thread 1: increment_if_not_zero() if (counter > 0) { { std::lock_guard g_{m}; return (--counter == 0); } std::mutex m; uint64_t counter{1}; }; Thread 1: increment_if_not_zero() std::lock_guard g_{m}; if (counter

required string endpoint = 3; required string bucketname = 4; required uint64 blockSize = 5; required uint64 chunkSize = 6; } mds.proto© XXX Page 4 of 11 import "curvefs/proto/common 1; required uint64 blockSize = 2; required FSType fsType = 3; optional common.Volume volume = 4; optional common.S3Info s3Info = 5; } message FsInfo { required uint32 fsId = 1; required FsStatus status = 3; required uint64 rootInodeId = 4; required uint64 capacity = 5; required uint64 blockSize = 6; required uint32 mountNum = 7; repeated MountPoint mountpoints

bool. 11 built-in integer numeric types (basic integer types): int8, uint8, int16, uint16, int32, uint32, int64, uint64, int, uint, and uintptr. two built-in floating-point numeric types: float32 and float64 complex types. Go also support two built-in type aliases, byte is a built-in alias of uint8. We can view byte and uint8 as the same type. rune is a built-in alias of int32. We can view rune and int32 as the type will occupy in memory at run time. For example, every value of the uint8 occupies 8 bits in memory. So the largest uint8 value is 255 (28-1), the largest int8 value is 127 (27-1), and the smallest