README
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ndn-dpdk/container/pcct
This package implements the PIT-CS Composite Table (PCCT), a non-thread-safe hash table that carries both the Pending Interest Table (PIT) and the Content Store (CS).
Each PCC entry contains PIT and CS entries for a combination of Interest/Data name and chosen delegation name in the forwarding hint.
It can store a PIT entry for MustBeFresh=0 (denoted "PitEntry0"), a PIT entry for MustBeFresh=1 (denoted "PitEntry1"), and a CS entry.
The main PccEntry type has one PccSlot providing room for one PIT entry or one CS entry.
A PccEntryExt can be allocated from the PCCT's mempool to provide two additional slots.
Regardless of available slots, each PCC entry can only have one each of PitEntry0, PitEntry1, and CS entry.
The C code for the PIT and the CS is also part of the csrc/pcct directory, in order to avoid circular dependencies, but the Go bindings and related documentation for each module are in their own separate packages.
Name Hash Table
The name hash table is indexed by Interest/Data and forwarding hint delegation names.
It uses the uthash library and stores the hash table head in the keyHt field of PcctPriv.
Hash table expansion has been disabled to provide more predictable performance.
DPDK's hash library is unsuitable for this hash table because it requires fixed-length keys, but NDN names are variable length, and padding them to a fixed maximum length would be too wasteful.
The PccKey type represents an index key of the name hash table.
For a PIT entry, PccKey contains the Interest name and, if the Interest carries a forwarding hint, the name of the chosen delegation.
For a CS entry, PccKey contains the Data name and, if the Interest used to retrieve this Data carried a forwarding hint, the name of the chosen delegation.
Interest/Data name and delegation name are copied into the PccKey, which has room for short and medium-length names.
If the names are too long to fit into the PccKey itself, PccKeyExt objects can be allocated from the PCCT's mempool to provide extra room.
Copying the names, rather than referencing them from the packet (usually an Interest), ensures the name buffers are NUMA-local and allows the packet buffer holding the Interest to be freed when the Interest is satisfied.
Searching the name hash table uses the PccSearch type instead of the PccKey type.
PccSearch contains pointers to linearized names.
Searching with a different type is made possible by customizing uthash's HASH_KEYCMP hook to use the PccKey_MatchSearch function instead of the built-in definition.
Calling code must supply the hash values.
The hash value for an index key without a forwarding hint is LName_ComputeHash(name).
The hash value for an index key with a forwarding hint is LName_ComputeHash(name) ^ LName_ComputeHash(delegation).
Token Hash Table
Each PCC entry can have an optional 48-bit token.
The token hash table is indexed by this token.
It uses DPDK's hash library, where the index key is the token padded to uint64_t, the hash value is in the lower 32 bits of the token, and the user data field is a PccEntry pointer.
A newly-inserted PCC entry does not have a token.
Calling code must invoke Pcct_AddToken to assign a token, and then it can invoke Pcct_FindByToken to retrieve that entry by token.
Documentation
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Overview ¶
Package pcct implements the PIT-CS Composite Table.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Config ¶
type Config struct {
PcctCapacity int `json:"pcctCapacity,omitempty"`
CsDirectCapacity int `json:"csDirectCapacity,omitempty"`
CsIndirectCapacity int `json:"csIndirectCapacity,omitempty"`
}
Config contains PCCT configuration.
type Pcct ¶
Pcct represents a PIT-CS Composite Table (PCCT).
func New ¶
func New(cfg Config, socket eal.NumaSocket) (pcct *Pcct, e error)
New creates a PCCT and initializes PIT and CS.
Source Files