* Add Linux NUMA "numastat" metrics
Read the `numastat` metrics from /sys/devices/system/node/node* when reading NUMA meminfo metrics.
* Update end-to-end test output.
* Add `numastat` metrics as counters.
* Add tests for error conditions.
* Refactor meminfo numa metrics struct
* Refactor meminfoKey into a simple struct of metric data.
This makes it easier to pass slices of metrics around.
* Refactor tests.
* Fixup: Add suggested fixes.
* Fixup: More fixes
* Add another scanner.Err() return
* Add "_total" to counter metrics.
It turns out, on some kernels (notably - CentOS6) there is an empty line
inserted at the beginning of /sys/devices/system/node/node*/meminfo
files. The leads to node_exporter crash on such kernels.
Fix this by checking for empty string first.
Signed-off-by: Pavel Borzenkov <pavel.borzenkov@gmail.com>
It is sometimes useful to understand the distribution of free/occupied
memory between NUMA nodes to deal with performance problems. To do so,
add new meminfo_numa collector that enables exporting of per node
statistics along with unit and end-to-end tests for it.
Signed-off-by: Pavel Borzenkov <pavel.borzenkov@gmail.com>
