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Design of a Diversified Router: Memory Usage. John DeHart jdd@arl.wustl.edu http://www.arl.wustl.edu/arl. QID(20b). QID. QID. QID. QID. QID. QID. QID. credit. credit. credit. credit. credit. Credit(32b). credit. credit. LC: Notes on Memory Usage. SRAM Adr(32b). Next Ptr(32b).
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Design of aDiversified Router: Memory Usage John DeHartjdd@arl.wustl.edu http://www.arl.wustl.edu/arl
QID(20b) QID QID QID QID QID QID QID credit credit credit credit credit Credit(32b) credit credit LC: Notes on Memory Usage SRAM Adr(32b) Next Ptr(32b) • 3 SRAM Channels of 8MB each per NP • 3 RDRAM Channels 0f 256MB 768 MB per NP • Shared between XScale and Microengines. • 640 32-bit words of Local Memory per MicroEngine • Parameters: • N: Max number of packets in the system at any given time. • M: Max number of queues that need to be supported • BatchSize: Number of slots in Scheduling Data Structure Segments (8 for now) • Data Structures Stored in SRAM: • Buffer Descriptors • 32 Bytes each • Number needed: N • IXP Queue Descriptors • 16 Bytes each • Number needed: M • QM Queue Data (QLen, Weight, Threshold) • 12 Bytes each • Number needed: M • Scheduling Data Structure Segments: • BatchSize*8 + 4B (address) + 4B (pointer to next) + 1 Bytes each • Number needed: (M/8) + x • Where x is the number of extra/spare needed to operate alogorithm • X <= 10 is probably sufficient • Data stored in DRAM: • Packet Buffers • 2KB each
Notes on Memory Usage • 1 SRAM Channel for IXP Queue Descs, QM Queue Data and Scheduling Data Structure: • 16*M + 12*M + ((M/8)+10)*(72) <= 8MB (0x800000 = 8388608) • 28*M + 9M + 720 <= 8MB (8388608) • 37*M <= 8387888 • M <= 226699 • So, lets say we will support 128K Queues (131071) • 17 bits of QID gives us a range of 0 – 1310171 • 1 SRAM Channel for Buffer Descriptors • 32*N <= 8MB (0x800000 = 8388608) • N <= 262144 (0x40000) • Max of 256K packets in the system • 1 SRAM Channel still free • On NPE this would be used for: • MR specific data region • MR configuration data • Etc. • DRAM usage for 256K Packets: • 256K * 2K per buffer = 512 MB • Out of 768MB available.
Local Memory Usage • What Blocks make use of Local Memory? • Specifically what blocks access tables in Local Memory that are updated by the Control Plane?
Extra • The next set of slides are for templates or extra information if needed
