tt_dispatch_prefetch_waiting_on_upstream
Name
Prometheus Metric Name
tt_dispatch_prefetch_waiting_on_upstream
Metric Path (tt-telemetry)
Schema:
{hostname}/tray{tray}/chip{chip}/cq{cq}/tt_dispatch_prefetch_waiting_on_upstream
Example path:
bh-glx-c09u02/tray1/chip2/cq0/tt_dispatch_prefetch_waiting_on_upstream
Description
A point-in-time flag indicating whether, at the moment of the telemetry read, the prefetch core for
this command queue (CQ) was stalled waiting on its upstream. The prefetch core sits at the front of
the fast-dispatch pipeline (host → prefetch core → dispatch core → worker cores); its upstream is
the host, so a true value means the prefetcher has run out of commands/data and is waiting for the
host to enqueue more.
Because it is sampled instantaneously once per collection interval (rather than counting events),
treat it as a coarse indicator. A value that is persistently true generally points to a
host-bound workload — the host is not feeding the command queue fast enough — rather than a
device-side bottleneck. Pair it with
tt_dispatch_prefetch_blocked_count to distinguish a single
long stall from many brief ones.
A separate metric is emitted for every command queue the chip can support (cq0, cq1, …). CQs
absent from a given read, and chips whose firmware bundle is below version 19.12.0, report the
default value of 0.
This is an integer flag (only ever 0 or 1) rather than a boolean so that it does not contribute
to the overall health status.
Values
Type: Integer
Units: None
Allowable values:
1: The prefetch core was waiting on the host for more work at read time.
0: The prefetch core was not waiting (also reported when the CQ was absent from the read or dispatch telemetry was unavailable).
Prometheus Labels
Label Name |
Value |
|---|---|
hostname |
The host from which the metric was collected. |
hall |
The datacenter hall where the host is located. Sourced from the Factory System Descriptor (FSD). |
aisle |
The datacenter aisle where the host is located. Sourced from the Factory System Descriptor (FSD). |
rack |
The rack number where the host is located. Sourced from the Factory System Descriptor (FSD). |
shelf_u |
The shelf U position in the rack where the host is located. Sourced from the Factory System Descriptor (FSD). |
tray |
The tray (UBB) that the device is located on. |
chip |
The ASIC location within the tray. |
cq |
The hardware command queue index ( |