Target modules for applying PEFT / LoRA on different models

I am looking at a few different examples of using PEFT on different models. The LoraConfig object contains a target_modules array. In some examples, the target modules are ["query_key_value"], sometimes it is ["q", "v"], sometimes something else.

I don't quite understand where the values of the target modules come from. Where in the model page should I look to know what the LoRA adaptable modules are?

One example (for the model Falcon 7B):

peft_config = LoraConfig(
    lora_alpha=lora_alpha,
    lora_dropout=lora_dropout,
    r=lora_r,
    bias="none",
    task_type="CAUSAL_LM",
    target_modules=[
        "query_key_value",
        "dense",
        "dense_h_to_4h",
        "dense_4h_to_h",
    ]

Another example (for the model Opt-6.7B):

config = LoraConfig(
    r=16,
    lora_alpha=32,
    target_modules=["q_proj", "v_proj"],
    lora_dropout=0.05,
    bias="none",
    task_type="CAUSAL_LM"
)

Yet another (for the model Flan-T5-xxl):

lora_config = LoraConfig(
 r=16,
 lora_alpha=32,
 target_modules=["q", "v"],
 lora_dropout=0.05,
 bias="none",
 task_type=TaskType.SEQ_2_SEQ_LM
)

Let's say that you load some model of your choice:

model = AutoModelForCausalLM.from_pretrained("some-model-checkpoint")

Then you can see available modules by printing out this model:

print(model)

You will get something like this (SalesForce/CodeGen25):

LlamaForCausalLM(
  (model): LlamaModel(
    (embed_tokens): Embedding(51200, 4096, padding_idx=0)
    (layers): ModuleList(
      (0-31): 32 x LlamaDecoderLayer(
        (self_attn): LlamaAttention(
          (q_proj): Linear(in_features=4096, out_features=4096, bias=False)
          (k_proj): Linear(in_features=4096, out_features=4096, bias=False)
          (v_proj): Linear(in_features=4096, out_features=4096, bias=False)
          (o_proj): Linear(in_features=4096, out_features=4096, bias=False)
          (rotary_emb): LlamaRotaryEmbedding()
        )
        (mlp): LlamaMLP(
          (gate_proj): Linear(in_features=4096, out_features=11008, bias=False)
          (down_proj): Linear(in_features=11008, out_features=4096, bias=False)
          (up_proj): Linear(in_features=4096, out_features=11008, bias=False)
          (act_fn): SiLUActivation()
        )
        (input_layernorm): LlamaRMSNorm()
        (post_attention_layernorm): LlamaRMSNorm()
      )
    )
    (norm): LlamaRMSNorm()
  )
  (lm_head): Linear(in_features=4096, out_features=51200, bias=False)
)

In my case, you can find the LLamaAttention module that contains q_proj, k_proj, v_proj, and o_proj. And this are some modules available for LoRA.

I suggest you reading more about which modules to use in LoRA paper.