dpdk: replace TSC clock with GetTime (gettimeofday) function v1 #11389
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Getting clock through Time Stamp Counter (TSC) can be precise and fast, however only for a short duration of time. The implementation across CPUs seems to vary. The original idea is to increment the counter with every tick. Then dividing the delta of CPU ticks by the CPU frequency can return the time that passed. However, the CPU clock/frequency can change over time, resulting in uneven incrementation of TSC. On some CPUs this is handled by extra logic. As a result, obtaining time through this method might drift from the real time. This commit therefore substitues TSC time retrieval by the standard system call wrapped in GetTime function - on Linux it is gettimeofday. Ticket: 7115
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Is there a performance impact? |
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I was playing around with it and no (major) performance impact was observed. |
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Information: QA ran without warnings. Pipeline 21332 |
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rebased version in #11409 |
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Getting time through the Time Stamp Counter (TSC) can be precise and fast, however only for a short duration of time.
The implementation across CPUs seems to vary. The original idea is to increment the counter with every tick. Then dividing the delta of CPU ticks by the CPU frequency can return the time that passed. However, the CPU clock/frequency can change over time, resulting in uneven incrementation of TSC. On some CPUs, this is handled by extra logic. As a result, obtaining time through this method might drift from real-time.
This commit therefore substitutes TSC time retrieval by the standard system call wrapped in the GetTime function - on Linux it is gettimeofday.
Ticket: 7115
https://redmine.openinfosecfoundation.org/issues/7115
Describe changes:
v1