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Optimization #5718

closed

time: compact alternative to struct timeval

Added by Victor Julien 2 months ago. Updated 1 day ago.

Status:
Closed
Priority:
Normal
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Description

struct timeval uses 16 bytes of space on 64 bit Linux. This is far more than needed. This structure is embedded in various memory and cache sensitive data structures:
- flow 2x (lastts, startts)
- packet (ts)
- defrag tracker (timeout)
- stream (pcap hdr storage)

timeval has 2 fields we care about: tv_sec (seconds since epoch), tv_usec (micro seconds, range 0-1000000).

If we'd use a simple uint64_t of usecs since epoch, we'd be able to express 1970-infinity.
We could further shrink it to 52 bits, which would express 1970-2100 - these 12 bits we'd further save could hold a vlan id?

E.g.:

uint64_t startts_usecs:52;
uint64_t vlan_id1:12;

When setting/checking the timestamp we'd need some helpers to set it from a struct timeval, be able to compare it with one, etc.

Actions #1

Updated by Jeff Lucovsky 11 days ago

  • Status changed from New to In Review
  • Assignee changed from OISF Dev to Jeff Lucovsky
Actions #2

Updated by Jeff Lucovsky 1 day ago

  • Status changed from In Review to Closed
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