#!/usr/bin/env python3
"""丟掉模型檔在系統 page cache 裡的頁（POSIX_FADV_DONTNEED）。

為什麼需要：量 SSD 讀取量之前一定要做，否則「上一輪留在核心 page cache」
會讓數字虛高（看起來像是 SSD 變快了，其實是記憶體）。

用法：
    python3 tools/drop_model_cache.py <model.gguf> [more files...]
"""
import os
import sys

POSIX_FADV_DONTNEED = 4
SYNC = 2


def drop(path: str) -> tuple[bool, str]:
    try:
        fd = os.open(path, os.O_RDONLY)
    except OSError as e:
        return False, str(e)
    try:
        size = os.fstat(fd).st_size
        os.posix_fadvise(fd, 0, size, POSIX_FADV_DONTNEED)
        os.fsync(fd)
        return True, f"{size} bytes"
    except (AttributeError, OSError) as e:
        return False, str(e)
    finally:
        os.close(fd)


def main() -> int:
    if len(sys.argv) < 2:
        print(__doc__)
        return 2
    rc = 0
    for p in sys.argv[1:]:
        if not os.path.exists(p):
            print(f"[drop] 找不到 {p}")
            rc = 1
            continue
        ok, info = drop(p)
        print(f"[drop] {'ok  ' if ok else 'fail'} {p} {info}")
        if not ok:
            rc = 1
    return rc


if __name__ == "__main__":
    sys.exit(main())