The total amount of memory currently swapped to disk. As with the CPU statistics, when run in normal mode, the first line that vmstat provides is the average values for all the rate statistics ( so and si) and the instantaneous value for all the numeric statistics ( swpd, free, buff, cache, active, and inactive). Table 3-2 provides a list of the memory statistics that vmstat can provide. This describes in detail how the kernel's memory is allocated and can be helpful to determine what area of the kernel is consuming the most memory. This is the same information that can be retrieved by typing cat/proc/slabinfo. It contains both memory and CPU statistics. This is a grab bag of differentstatistics about the system since it has booted.
This changes the default output of memory statistics to indicate the active/inactive amount of memory rather than information about buffer and cache usage. Table 3-1 describes the options that vmstat accepts. The added command-line options enable you to get the performance statistics about how the Linux kernel is using memory. In addition to the CPU statistics vmstat can provide, you can invoke vmstat with the following command-line options when investigating memory statistics:Īs before, you can run vmstat in two modes: sample mode and average mode.
3.2.1.1 System-Wide Memory-Related Options
In addition to the CPU performance statistics described in the previous chapter, it can also tell you the following:Īs you can see, vmstat provides (via the statistics it displays) a wealth of information about the health and performance of the system in a single line of text. vmstat (Virtual Memory Statistics) IIĪs you have seen before, vmstat can provide information about many different performance aspects of a system-although its primary purpose, as shown next, is to provide information about virtual memory system performance. Here begins our discussion of performance tools that enable you to extract the memory performance information described previously.
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