This section explains the concepts of generative AI scale unit (GSU) and burndown rates. Provisioned Throughput is calculated and priced using generative AI scale units (GSUs) and burndown rates.
GSU and burndown rate
A generative AI scale unit (GSU) is a measure of throughput for your prompts and responses. This amount specifies how much throughput to provision a model with.
A burndown rate is a ratio that converts the input-and-output characters to input characters per second (throughput). This ratio is used to produce a standard unit across models.
Different models use different amounts of throughput. For information about the minimum GSU purchase amount and increments for each model, see Supported models and burndown rates in this document.
This equation demonstrates how throughput is calculated:
inputs_per_query = inputs_across_modalities_converted_using_burndown_rates
outputs_per_query = outputs_across_modalities_converted_using_burndown_rates
throughput_per_second = (inputs_per_query + outputs_per_query) * queries_per_second
The calculated throughput per second determines how many GSUs that you need for your use case.
Example of estimating your Provisioned Throughput needs
To estimate your Provisioned Throughput needs, use the estimation tool in the Google Cloud console. The following example illustrates the process of estimating the amount of Provisioned Throughput for your model. The region isn't considered in the estimation calculations.
This table provides the burndown rates for gemini-1.5-flash that you can use to follow the example.
| Model | Throughput per GSU (chars/sec) | Minimum GSU purchase increment | Burndown rates | |
|---|---|---|---|---|
| Gemini 1.5 Flash | Less than or equal to 128,000 context window: 54,000 Greater than 128,000 context window: 27,000 |
1 | Less than or equal to 128,000 context window: 1 input char = 1 char 1 output char = 4 chars 1 image = 1,067 chars 1 video per second = 1,067 chars 1 audio per second = 107 chars |
Greater than 128,000 context window: 1 input char = 2 chars 1 output char = 8 chars 1 image = 2,134 chars 1 video per second = 2,134 chars 1 audio per second = 214 chars |
Gather your requirements.
In this example, your requirement is to ensure that you can send 2,000 characters with 2 images and receive 300 characters of output for 10 queries per second using
gemini-1.5-flash.This step means that you understand your use case, because you have identified the size of your inputs and outputs, the number of queries per second (QPS), and your model.
To estimate your throughput, specify your model. In this example, your model is
gemini-1.5-flash.Specify the type of input, and identify the burndown rate. Use the burndown rates table to identify the burndown rate based on your type of input.
An image's burndown rate for the
gemini-1.5-flashmodel is 1,067 characters.
Calculate your throughput.
Multiply the number of images by the burndown rate for the input type for your specific model.
2 images * 1,067 input characters per image = 2,134 input characters
Your total output characters is 300. Return to the burndown rates table, and find the burndown rate for output characters (four characters per output character) for your specific model (
gemini-1.5-flash).300 output characters * 4 characters per output character = 1,200 converted input characters
Add your totals together.
2,000 input characters + 2,134 converted input characters for the images + 1,200 converted input characters for the output = 5,334 converted input characters per query
Multiply the characters per query by your expected queries per second to get the total throughput per second.
5,334 converted input characters per query * 10 QPS = 53,340 total converted input characters per second
Calculate your GSUs.
The GSUs are the total throughput per second divided by throughput per GSU from the burndown table.
53,340 total converted input chars per second ÷ 54,000 throughput per GSU = 0.988 GSUs
The minimum GSU purchase increment for
gemini-1.5-flashis 1, which meets your requirement.