Int32 Operation code If operation equals op_response: Int32 Object handle Int64 Object ID Buffer Data (meaning depends on the operation). Byte[] Status vector  Information about parsing the SQL response Int32 Operation code If operation equals op_sql_response: Int32 Message count Buffer Response data (meaning depends on the operation). 2.3. Fetch response Chapter 2. Responses 4 that there are no more rows. Int32 Count of rows following response  The data rows are not in a buffer as described in Data types, but as a sequence of data rows, see Reading row data. 2.4. Slice response

fixed size, such as 64KB. You can tune this by: a. hbase.server.allocator.buffer.size b. hbase.server.allocator.max.buffer.count 2. Set another minimal off-heap allocation size, only when the desired so we can only update the checksum value incrementally by copying the bytes into a small heap buffer (such as byte[256]). Actually, almost all of the HFile Block are about 64KB, so it would be ByteBuffers; 2. Uncompress the off-heap ByteBuffers into a small heap buffer incrementally; 3. Copy the bytes from small heap buffer into off-heap ByteBuffers, which is wrapped as the unpack HFileBlock

SSDs ................................................................... 5 4. Flush Method and Buffer Pool ........................................................................................... Method and Buffer Pool BKM Switch the flush_method to ‘O_DIRECT’ MySQL uses its buffer pool as disk cache, rather than using Linux filesystem as buffer space. BKM Increase the buffer pool from from 3GB to 12GB Larger buffer pool improves performance for all storage types. After considerable experimentation and analysis, we switched the flush_method to ‘O_DIRECT’, and then stopped using Linux’s

page-level share/exclusive locks are used to control read/write access to table pages in the shared buffer pool. These locks are released immediately after a row is fetched or updated. Application developers that do not actually need many temporary buffers is only a buffer descriptor, or about 64 bytes, per increment in temp_buffers. However if a buffer is actually used an additional 8192 bytes will be consumed vacuum_cost_page_hit (integer) The estimated cost for vacuuming a buffer found in the shared buffer cache. It represents the cost to lock the buffer pool, lookup the shared hash table and scan the content of

page-level share/exclusive locks are used to control read/write access to table pages in the shared buffer pool. These locks are released immediately after a row is fetched or updated. Application developers that do not actually need many temporary buffers is only a buffer descriptor, or about 64 bytes, per increment in temp_buffers. However if a buffer is actually used an additional 8192 bytes will be consumed vacuum_cost_page_hit (integer) The estimated cost for vacuuming a buffer found in the shared buffer cache. It represents the cost to lock the buffer pool, lookup the shared hash table and scan the content of

page-level share/exclusive locks are used to control read/write access to table pages in the shared buffer pool. These locks are released immediately after a row is fetched or updated. Application developers buffers is 439 Chapter 18. Server Configuration only a buffer descriptor, or about 64 bytes, per increment in temp_buffers. However if a buffer is actually used an additional 8192 bytes will be consumed vacuum_cost_page_hit (integer) The estimated cost for vacuuming a buffer found in the shared buffer cache. It represents the cost to lock the buffer pool, lookup the shared hash table and scan the content of

page-level share/exclusive locks are used to control read/write access to table pages in the shared buffer pool. These locks are released immediately after a row is fetched or updated. Application developers that do not actually need many temporary buffers is only a buffer descriptor, or about 64 bytes, per increment in temp_buffers. However if a buffer is actually used an additional 8192 bytes will be consumed vacuum_cost_page_hit (integer) The estimated cost for vacuuming a buffer found in the shared buffer cache. It represents the cost to lock the buffer pool, lookup the shared hash table and scan the content of

图片来源：Systems Performance: Enterprise and the Cloud，中译本《性能之巅》， 作者Brendan Gregg 11 缓冲区Buffer Pool page … Buffer Pool Manager (Main Memory) Access Methods and other components dirty bit reference count 事务提交时，所修改的页面不需要强制刷回到持久存储中 ■ Steal / No-Steal Steal: 允许Buffer Pool里未提交事务所修改的脏页刷回到持久存储 No-steal: 不允许Buffer Pool里未提交事务所修改的脏页刷到持久存储中 缓冲区管理策略Buffer Management Policy 13 ■ Force策略的问题 对持久存储器进行频繁的随机写操作，性能下降。 No-Force / Steal 有更好的性能，但是怎么保证事务的原子性和持久 性？ ❏ No-Force: 事务提交，所修改的数据页没有刷回至持久存储，如果发生断电 或者系统崩溃。 ❏ Steal: Buffer Pool中未提交的事务所修改的脏页刷回到持久存储，如果发生 断电或者系统崩溃。 缓冲区管理策略 14 ■ No-Force → Redo Log 事务提交时，数据页不需要刷回持久存储，为了保证持久性，先把Redo

page-level share/exclusive locks are used to control read/write access to table pages in the shared buffer pool. These locks are released immediately after a row is fetched or updated. Application developers that do not actually need many temporary buffers is only a buffer descriptor, or about 64 bytes, per increment in temp_buffers. However if a buffer is actually used an additional 8192 bytes will be consumed vacuum_cost_page_hit (integer) The estimated cost for vacuuming a buffer found in the shared buffer cache. It represents the cost to lock the buffer pool, lookup the shared hash table and scan the content of

page-level share/exclusive locks are used to control read/write access to table pages in the shared buffer pool. These locks are released immediately after a row is fetched or updated. Application developers that do not actually need many temporary buffers is only a buffer descriptor, or about 64 bytes, per increment in temp_buffers. However if a buffer is actually used an additional 8192 bytes will be consumed vacuum_cost_page_hit (integer) The estimated cost for vacuuming a buffer found in the shared buffer cache. It represents the cost to lock the buffer pool, lookup the shared hash table and scan the content of