haskell-为什么我的并行代码运行得很差？

我一直在尝试并行化Haskell代码，但速度越来越慢，所以我制作了一些示例代码来说明我的问题，这里是串行代码：

module Main where

import System.Environment

sumRangeSquares :: (Num a, Enum a) => a -> a -> a
sumRangeSquares start end = sum $ map (^2) [start .. end]

main :: IO ()
main = do
    [start, end] <- map read <$> getArgs
    print $ sumRangeSquares start end

编译时使用stack ghc -- -O2 -rtsopts -eventlog -threaded src/Main.hs并与time ./src/Main 1 10000000，大约在0.4秒内完成

现在，明显的平行对应物是：

module Main where

import Control.Parallel.Strategies
import System.Environment

sumRangeSquares :: (Num a, Enum a) => a -> a -> a
sumRangeSquares start end = sum $ parMap rseq (^2) [start .. end]

main :: IO ()
main = do
    [start, end] <- map read <$> getArgs
    print $ sumRangeSquares start end

以相同的方式编译并运行time ./src/Main 1 10000000 +RTS -N4 -lf -s耗时6秒以上

以下是创建的日志-s:

   2,661,959,552 bytes allocated in the heap
   1,891,228,032 bytes copied during GC
     468,753,512 bytes maximum residency (12 sample(s))
     307,102,616 bytes maximum slop
            1226 MiB total memory in use (0 MB lost due to fragmentation)

                                     Tot time (elapsed)  Avg pause  Max pause
  Gen  0      1837 colls,  1837 par   10.483s   2.705s     0.0015s    0.0080s
  Gen  1        12 colls,    11 par    5.157s   1.391s     0.1159s    0.5573s

  Parallel GC work balance: 26.09% (serial 0%, perfect 100%)

  TASKS: 10 (1 bound, 9 peak workers (9 total), using -N4)

  SPARKS: 10000000 (9998153 converted, 1847 overflowed, 0 dud, 0 GC'd, 0 fizzled)

  INIT    time    0.038s  (  0.038s elapsed)
  MUT     time    6.995s  (  2.158s elapsed)
  GC      time   15.639s  (  4.096s elapsed)
  EXIT    time    0.001s  (  0.005s elapsed)
  Total   time   22.673s  (  6.297s elapsed)

  Alloc rate    380,577,209 bytes per MUT second

  Productivity  30.8% of total user, 34.3% of total elapsed


real    0m6.374s
user    0m16.889s
sys 0m5.859s

下面是事件日志，如中所示threadscope Main.eventlog.

如图所示，有很多空闲时间，所有四个 HEC 在相对相同的时间运行和空闲。此外，还有很多较长的空闲时间，以及不平衡的火花池和火花创建。