ONL Stats Engine

1
ONL Stats Engine
David M. ZarApplied Research LaboratoryComputer
Science and Engineering Department
2
Stats Engine

• The Stats Engine will be a single ME devoted to
  accepting messages in a scratch ring and
  performing increment and add operations to
  counters.
• All MEs that need to update counters will use the
  Stats Engine
• Operations supported will be
• Atomic increment (1)
• Atomic add (data)
• Format of the commands will be

3
Opcodes

• Opcode
• 0011 1, data pre-q counter specified in Index
• 0111 1, data post-q counter specified in Index
• 0010 1 pre-q counter specified in Index
• 0110 1 post-q counter specified in Index
• 0001 data pre-q counter specified in Index
• 0101 data post-q counter specified in Index
• 1011 1, data register specified in Index
• 1010 1 register specified in Index

4
Stats Counters

• Each Index specifies a group of four counters
• Pre-Q packet count
• Pre-Q byte count
• Post-Q packet count
• Post-Q byte count
• The packet counters get updated when the 1
  instructions are specified (opcodes 0-1-)
• The byte counter get updated when the data
  instructions are specified (opcodes 0--1)
• For plug-ins, the use for each counter can be
  redefined but the opcodes do not change (i.e.
  each stats index corresponds to two incrementers
  and two adders).

5
Stats Registers

• For system-wide counters, we define a separate
  set of registers to handle them.
• RX (packet and byte, 5 ports ? 10 words)
• TX (packet and byte, 5 ports ? 10 words)
• Drop counts (10 words)
• Plug-in use (four per plug-in ? 20 words)
• 10101020 50 so reserve 64 words for these
• The register gets incremented when the 1
  instructions are specified (opcodes 101-)
• The register gets added to updated when the data
  instructions are specified (opcodes 10-1)
• The RX and TX counters will be assigned on
  even-word boundaries (lsb 0) so we associate
  the packet and byte coutners, together, and can
  do the 1, data instruction on them in one
  command
• For plug-ins, the allocation of each register is
  under the control of the plug-in.

6
Stats Counter Priority

• There are two levels of priority for Stats
  Counters
• High-priority (high-speed) are kept in local
  memory. There are 64 sets of counters for the
  router and 64 for the plug-ins
• Low-priority (low-speed) are in SRAM. There are
  216-128 65408 of these.
• Stats Counters 0-127 point to the high-priority
  counters while 128-65535 are low-priority
  counters.
• Using low-priority Stats Counters to count events
  that happen at high speed may degrade system
  performance (being a pre-Q counter on a
  high-priority queue, for example)
• Plug-ins need to be aware of the segmentation of
  priority so they can use the proper priority
  counters based on needs
• Stats Registers are always high-priority
• One ME thread will be used to write 8W chunks of
  the local memory counters/registers to SRAM so
  that each counter/register is updated in SRAM
  several times a second.

7
Local Memory Map
Status Registers 0 63
Reserved 64 127
Stats Counters (router) 644W 256W 128 383
Stats Counters (plug-ins) 644W 256W 384 639