@@ -11,12 +11,12 @@ When the server is running at full load, look for the following in the log:
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@@ -11,12 +11,12 @@ When the server is running at full load, look for the following in the log:
### Tune Your Request Submission Speed
### Tune Your Request Submission Speed
`#queue-req` indicates the number of requests in the queue. If you frequently see `#queue-req == 0`, it suggests you are bottlenecked by the request submission speed.
`#queue-req` indicates the number of requests in the queue. If you frequently see `#queue-req == 0`, it suggests you are bottlenecked by the request submission speed.
A healthy range for `#queue-req` is `50 - 500`.
A healthy range for `#queue-req` is `50 - 500`.
On the other hand, do not make `#queue-req` too large because it will also increase the scheduling overhead on the server.
On the other hand, do not make `#queue-req` too large because it will also increase the scheduling overhead on the server, especially when using the default longest-prefix-match schedule policy (`--schedule-policy lpm`).
### Tune `--schedule-conservativeness`
### Tune `--schedule-conservativeness`
`token usage` indicates the KV cache memory utilization of the server. `token usage > 0.9` means good utilization.
`token usage` indicates the KV cache memory utilization of the server. `token usage > 0.9` means good utilization.
If you frequently see `token usage < 0.9` and `#queue-req > 0`, it means the server is too conservative about taking in new requests. You can decrease `--schedule-conservativeness` to a value like 0.3.
If you frequently see `token usage < 0.9` and `#queue-req > 0`, it means the server is too conservative about taking in new requests. You can decrease `--schedule-conservativeness` to a value like 0.3.
The case of serving being too conservative can happen when users send many requests with a large `max_new_tokens` but the requests stop very early due to EOS or stop strings.
The case of server being too conservative can happen when users send many requests with a large `max_new_tokens` but the requests stop very early due to EOS or stop strings.
On the other hand, if you see `token usage` very high and you frequently see warnings like
On the other hand, if you see `token usage` very high and you frequently see warnings like
`decode out of memory happened, #retracted_reqs: 1, #new_token_ratio: 0.9998 -> 1.0000`, you can increase `--schedule-conservativeness` to a value like 1.3.
`decode out of memory happened, #retracted_reqs: 1, #new_token_ratio: 0.9998 -> 1.0000`, you can increase `--schedule-conservativeness` to a value like 1.3.
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@@ -25,17 +25,17 @@ If you see `decode out of memory happened` occasionally but not frequently, it i
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@@ -25,17 +25,17 @@ If you see `decode out of memory happened` occasionally but not frequently, it i
### Tune `--dp-size` and `--tp-size`
### Tune `--dp-size` and `--tp-size`
Data parallelism is better for throughput. When there is enough GPU memory, always favor data parallelism for throughput.
Data parallelism is better for throughput. When there is enough GPU memory, always favor data parallelism for throughput.
### Avoid out-of-memory by tuning `--chunked-prefill-size`, `--mem-fraction-static`, `--max-running-requests`
### Avoid out-of-memory by Tuning `--chunked-prefill-size`, `--mem-fraction-static`, `--max-running-requests`
If you see out of memory (OOM) errors, you can decrease these parameters.
If you see out of memory (OOM) errors, you can decrease these parameters.
If OOM happens during prefill, try to decrease `--chunked-prefill-size` to `4096` or `2048`.
If OOM happens during prefill, try to decrease `--chunked-prefill-size` to `4096` or `2048`.
If OOM happens during decoding, try to decrease `--max-running-requests`.
If OOM happens during decoding, try to decrease `--max-running-requests`.
You can also try to decrease `--mem-fraction-static`, which reduces the memory usage of the KV cache memory pool and helps both prefill and decoding.
You can also try to decrease `--mem-fraction-static`, which reduces the memory usage of the KV cache memory pool and helps both prefill and decoding.
### Try advanced options
### Try Advanced Options
- To enable the experimental overlapped scheduler, add `--enable-overlap-scheduler`. It overlaps CPU scheduler with GPU computation and can accelerate almost all workloads. This does not work for constrained decoding currenly.
- To enable the experimental overlapped scheduler, add `--enable-overlap-scheduler`. It overlaps CPU scheduler with GPU computation and can accelerate almost all workloads. This does not work for constrained decoding currenly.
- To enable torch.compile acceleration, add `--enable-torch-compile`. It accelerates small models on small batch sizes. This does not work for FP8 currenly.
- To enable torch.compile acceleration, add `--enable-torch-compile`. It accelerates small models on small batch sizes. This does not work for FP8 currenly.
### (Minor) Tune `--schedule-policy`
### Tune `--schedule-policy`
If you have many shared prefixes, use the default `--schedule-policy lpm`. `lpm` stands for longest prefix match.
If the workload has many shared prefixes, use the default `--schedule-policy lpm`. `lpm` stands for longest prefix match.
When you have no shared prefixes at all or you always send the requests with the shared prefixes together,
When you have no shared prefixes at all or you always send the requests with the shared prefixes together,
you can try `--schedule-policy fcfs`. `fcfs` stands for first come first serve.
you can try `--schedule-policy fcfs`. `fcfs` stands for first come first serve. `fcfs` has a lower scheduling overhead.
