Modes of emission
QNX SDP8.0System ArchitectureDeveloperUser
Apart from applying the various filters to control the event
stream, you can also specify one of two modes the kernel can
use to emit events:
- fast mode
- Emits only the most pertinent information (e.g., only two kernel call arguments) about an event.
- wide mode
- Generates more information (e.g., all kernel call arguments) for the same event.
The trade-off here is one of speed vs knowledge: fast mode delivers less data, while wide mode packs much more information for each event. Either way, you can easily tune your system, because these modes work on a per-event basis.
As an example of the difference between the fast and wide
emission modes, let's look at the kinds of information we
might see for a
MsgSendv()
call entry:
Fast mode data | Number of bytes for the event |
---|---|
Connection ID | 4 bytes |
Message data | 4 bytes (the first 4 bytes usually comprise the header) |
Total emitted: 8 bytes |
Wide mode data | Number of bytes for the event |
---|---|
Connection ID | 4 bytes |
# of parts to send | 4 bytes |
# of parts to receive | 4 bytes |
Message data | 4 bytes (the first 4 bytes usually comprise the header) |
Message data | 4 bytes |
Message data | 4 bytes |
Total emitted: 24 bytes |
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