484Performance monitoring and tuning

Tuning VxVM

tracing event records. As trace buffers are requested to be stored in the kernel, the memory for them is drawn from this pool.

Increasing this size can allow additional tracing to be performed at the expense of system memory usage. Setting this value to a size greater than can readily be accommodated on the system is inadvisable.

The default value for this tunable is 131072 bytes (128KB).

voliot_iobuf_max

The maximum buffer size that can be used for a single trace buffer. Requests of a buffer larger than this size are silently truncated to this size. A request for a maximal buffer size from the tracing interface results (subject to limits of usage) in a buffer of this size.

The default size for this buffer is 65536 bytes (64KB).

Increasing this buffer can provide for larger traces to be taken without loss for very heavily used volumes. Care should be taken not to increase this value above the value for the voliot_iobuf_limit tunable value.

voliot_max_open

The maximum number of tracing channels that can be open simultaneously. Tracing channels are clone entry points into the tracing device driver. Each vxtrace process running on a system consumes a single trace channel.

The default number of channels is 32. The allocation of each channel takes up approximately 20 bytes even when not in use.

volpagemod_max_memsz

The amount of memory, measured in kilobytes, that is allocated for caching FastResync and cache object metadata. This tunable has a default value of 6144KB (6MB) of physical memory.