29.12.22.11 The system_memory_stats Table

System memory statistics.

mysql> select * from performance_schema.system_memory_stats\G
*************************** 1. row ***************************
       TIMESTAMP: 2026-10-01 09:52:33
     TOTAL_BYTES: 8022503424
      FREE_BYTES: 840933376
      USED_BYTES: 4688453632
 AVAILABLE_BYTES: 2804424704
   BUFFERS_BYTES: 4489216
    CACHED_BYTES: 2066862080
      SLAB_BYTES: 421765120
SWAP_TOTAL_BYTES: 4236242944
 SWAP_FREE_BYTES: 4006621184
 SWAP_USED_BYTES: 229621760
         SWAP_IN: 4808998912
        SWAP_OUT: 2948497408
1 row in set (0.001 sec)

The system_memory_stats table has the following columns:

• TIMESTAMP: Time when the measurement was taken.

• TOTAL_BYTES: Total usable system memory, in bytes.

• FREE_BYTES: Unused memory.

• USED_BYTES: Memory used. Calculated as TOTAL_BYTES - FREE_BYTES - CACHED_BYTES - BUFFERS_BYTES - SLAB_BYTES.

• AVAILABLE_BYTES: Estimated memory available for starting new applications, in bytes.

• BUFFERS_BYTES: Temporary storage for raw disk blocks.

• CACHED_BYTES: In-memory cache for files read from the disk (the page cache).

• SLAB_BYTES: In-kernel data structures cache.

• SWAP_TOTAL_BYTES: Total amount of swap space available.

• SWAP_FREE_BYTES: Total amount of memory which has been evicted from RAM and is temporarily on disk.

• SWAP_USED_BYTES: Used swap space. Calculated as SWAP_TOTAL_BYTES - SWAP_FREE_BYTES.

• SWAP_IN: Amount of memory swapped in from disk, kB/s.

• SWAP_OUT: Amount of memory swapped out from disk, kB/s.