Environment variable best practices

Avoid reading environment variables directly in performance-critical code paths, especially during model forward passes or hot loops. Instead, read and cache environment variables during initialization or use dedicated helper functions for consistent handling.

Use standardized helper functions like get_bool_env_var() instead of direct os.getenv() calls for better type safety and consistency. Follow clear naming conventions for environment variables, using descriptive prefixes like SGLANG_ for project-specific settings.

Example of what to avoid:

def forward_decode(self):
    # BAD: Reading env var in forward pass
    if os.getenv("USE_W4A8") != "1" and deep_gemm_wrapper.ENABLE_JIT_DEEPGEMM:
        # performance-critical code

Better approach:

def __init__(self):
    # GOOD: Cache env var during initialization
    self.use_w4a8 = get_bool_env_var("SGLANG_USE_W4A8")
    
def forward_decode(self):
    # GOOD: Use cached value
    if not self.use_w4a8 and deep_gemm_wrapper.ENABLE_JIT_DEEPGEMM:
        # performance-critical code

This practice improves performance by avoiding repeated system calls and ensures consistent configuration handling across the codebase.