Collectd Metrics and Events

if pkg_recv > 1

latency_stddev = sqrt (((((double) pkg_recv) * latency_squared) - (latency_total * latency_total)) / ((double) (pkg_recv * (pkg_recv - 1))));

The total number of packets received that were less than 64 octets in length (excluding framing bits but including FCS octets) and had either a bad Frame Check Sequence (FCS) with an integral number of octets (FCS Error) or a bad FCS with a non-integral number of octets (Alignment Error).

Virtual memory makes it easy for several processes to share memory [TM1] .

Each process has its own virtual address space, which is mapped to physical memory by the operating system” [TM2] . The process views the virtual memory address space as a contiguous/linear address space, but in reality – the virtual addresses need to be mapped to physical addresses, this is typically done by the Memory Management Unit (MMU) on the CPU.

“There are two ways to enable the system to manage large amounts of memory:

• Increase the number of page table entries in the hardware memory management unit
• Increase the page size/use huge pages à to reduce the number of lookups

The first method is expensive, since the hardware memory management unit in a modern processor only supports hundreds or thousands of page table entries. Additionally, hardware and memory management algorithms that work well with thousands of pages (megabytes of memory) may have difficulty performing well with millions (or even billions) of pages. This results in performance issues: when an application needs to use more memory pages than the memory management unit supports, the system falls back to slower, software-based memory management, which causes the entire system to run more slowly.

Huge pages are blocks of memory that come in 2MB and 1GB sizes. The page tables used by the 2MB pages are suitable for managing multiple gigabytes of memory, whereas the page tables of 1GB pages are best for scaling to terabytes of memory” [TM3] 

More info on virtual memory and TLB lookups can be found:

1. http://www.tldp.org/LDP/tlk/mm/memory.html
2. https://lwn.net/Articles/253361/

A higher IPC means that the processor can get more work done per unit time, which generally translates to faster application performance [0]

"Ideally every instruction a CPU gets should be read, executed and finished in one cycle, however that is never the case. The processor has to take the instruction, decode the instruction, gather the data (depends on where the data is), perform work on the data, then decide what to do with the result. Moving has never been more complicated, and the ability for a processor to hide latency, pre-prepare data by predicting future events or keeping hold of previous events for potential future use is all part of the plan. All the meanwhile there is an external focus on making sure power consumption is low and the frequency of the processor can scale depending on what the target device actually is". [1]

0 https://www.nextplatform.com/2016/03/31/examining-potential-hpc-benefits-new-intel-xeon-processors/

1 http://www.anandtech.com/show/9482/intel-broadwell-pt2-overclocking-ipc/3

main thread

emc hits

Number of packets hitting Exact Match Cache.

Plugin instance: pmd thread can be different combinations of <numa_id> and <core_id>.

e.g: ovs_pmd_stats-pmd_thread_numa_id_0_core_id_5

megaflow hits

Average number of subtable lookups for every hit.

Number of packets not matching any existing flow.

Number of packets destined for user space process but subsequently dropped before reaching userspace.

polling cycles

Number of cycles used for polling packets.

processing cycles

Number of cycles used for processing incoming packets.

Average number of cycles per packet.

avg processing cycles per packet

Correctable Errors include:
Receiver Error Status
Bad TLP Status
Bad DLLP Status
REPLAY_NUM Rollover
Replay Timer Timeout
Advisory Non-Fatal
Corrected Internal
Header Log Overflow

Uncorrectable Errors include:
Data Link Protocol
Surprise Down
Poisoned TLP
Flow Control Protocol
Completion Timeout
Completer Abort
Unexpected Completion
Receiver Overflow
Malformed TLP
ECRC Error Status
Unsupported Request
ACS Violation
Internal
MC blocked TLP
Atomic egress blocked
TLP prefix blocked

Warning for Corrected Memory Errors

Failure for Uncorrected Memory Errors

Failure on failure to connect to the mcelog socket/ if connection is lost

OK on connection to mcelog socket

OKAY:

• VIR_DOMAIN_NOSTATE
• VIR_DOMAIN_RUNNING
• VIR_DOMAIN_SHUTDOWN
• VIR_DOMAIN_SHUTOFF

WARNING:

• VIR_DOMAIN_BLOCKED
• VIR_DOMAIN_PAUSED
• VIR_DOMAIN_PMSUSPENDED

FAILURE:

• VIR_DOMAIN_CRASHED