# tt_device_dram_used_megabytes

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## Name

### Prometheus Metric Name

```
tt_device_dram_used_megabytes
```

### Metric Path (tt-telemetry)

Schema:

```
{hostname}/tray{tray}/chip{chip}/dram/tt_device_dram_used_megabytes
```

Example path:

```
bh-glx-c09u02/tray1/chip2/dram/tt_device_dram_used_megabytes
```

## Description

The amount of DRAM currently allocated on the chip by tt-metal, summed across every process attached to the chip, in mebibytes (1 MiB = 1024×1024 B), rounded to the nearest integer.

The underlying byte count is read from the `total_dram_allocated` field of tt-metal's per-device shared-memory allocator-stats region (`/dev/shm/tt_device_<asic_id>_memory`). tt-telemetry maps the region read-only and never writes to it.

If no tt-metal process has ever touched the chip on this host the SHM file is absent and the metric reports `0`; the reader retries on every cycle. If the SHM region exists but its layout version disagrees with what tt-telemetry was built against, the metric reports `0` and a warning is logged once. The layout contract is the `version` field of the SHM struct (currently `3`).

For multi-chip mesh devices (e.g. N300, Galaxy) the shared-memory region currently aggregates allocations across the gateway chip and any remote chips reached through it, all reported under the gateway's `tray`/`chip` labels. Per-chip breakdown for mesh devices is a planned follow-up.

## Values

**Type:** Unsigned Integer

**Units:** Megabytes (MB) — reported as mebibytes (1 MiB = 1024×1024 B), rounded to the nearest integer.

**Allowable values:**
A non-negative integer. `0` means either no allocations are live or the SHM region is unavailable for this chip.

## 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.|
|unit|The unit of measurement. Always `"MB"` for this metric.|