free cache buffer

cache buffer


1, total: the actual total amount of physical memory
2, used: this piece must be carefully Possibly part of the cache is not actually used.
3, free: unallocated memory
4, shared: shared memory
5, buffers: the remaining amount of buffers allocated by the system but not used. Note that this is not the total amount, but the unallocated amount
6, cached: The remaining amount of cache allocated by the system but not used. The difference between buffer and cache is described later.

7, buffers/cache used: this is the usage of buffers and cache, that is, the usage of actual memory, this is very important, here is the actual usage of memory

8, buffers/cache free: unused buffers With the sum of cache and unallocated memory, this is the current actual available memory of the system. Be careful, here is the sum of the three, that is, the first row of free+buffers+cached, not only the sum of unused buffers and cache, but also free (unallocated sum)

9, swap, I think everyone understands this, the total amount of swap partitions, the amount of usage, the remaining amount

I think I made it clear the





difference between cache and buffer:
    Cache: Cache is a small but high-speed memory located between the CPU and main memory. Since the speed of the CPU is much higher than that of the main memory, the CPU needs to wait for a certain period of time to directly access data from the memory. The Cache stores a part of the data that the CPU has just used or recycled. When the CPU uses this part of the data again, it can be retrieved from the Cache In this way, the waiting time of the CPU is reduced and the efficiency of the system is improved. Cache is further divided into Level 1 Cache (L1 Cache) and Level 2 Cache (L2 Cache). L1 Cache is integrated inside the CPU. In the early days, L2 Cache was generally welded on the motherboard, but now it is also integrated inside the CPU. The common capacity is 256KB. or 512KB L2 Cache.
    Buffer: Buffer, an area used to store data transferred between devices with different speeds or different priorities. Through the buffer, the mutual waiting between the processes can be reduced, so that when the data is read from the slow device, the operation process of the fast device is not interrupted.
    Buffer and cache in Free: (they all occupy memory):
    buffer: as the memory of the buffer cache, which is the read and write buffer of the block device.
    Cache: as the memory of the page cache,
    if the cache value of the file system is very large, It shows that there are many files in the cache. If frequently accessed files can be cached, then the read IO of the disk will be very small.