pickle.load() significantly slows down with each call on Windows11 but not on Linux
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Description
Bug report
Bug description:
My task is to read millions of numpy images and get a region dynamically. The application dictates that the images are stored in batches of about 3000 to 6000 in files. These files contain a pickled dict of numpy arrays. On Windows, reading gets dramatically slower with each call, see logs below. These logs are run on two laptops with completely identical hardware, including 40GB of RAM. While Windows is much slower anyways, it should not get slower with each call?
import os
import pickle
import time
import platform
import sys
import numpy as np
import psutil
filePath = r'C:\images.pkl'
print(f"Versions: {platform.system()=}, {platform.release()=}, {platform.version()=}, {sys.version=}, {np.__version__=}")
imagesDict = {i: np.random.randint(0, 255, (300, 300), dtype=np.uint8) for i in range(4000)}
with open(filePath, 'wb') as file:
pickle.dump(imagesDict, file, pickle.HIGHEST_PROTOCOL)
thumbs = []
num_image_sets = 0
durations_s_sum = 0.
for i in range(500):
start_s = time.perf_counter()
with open(filePath, 'rb') as file:
imagesDict: dict[int, np.ndarray] = pickle.load(file)
for key in imagesDict.keys():
image = imagesDict[key]
thumb = image[:50, :50].copy()
thumbs.append(thumb)
durations_s_sum += (time.perf_counter() - start_s)
num_image_sets += 1
if 50 <= num_image_sets:
memory_info = psutil.Process(os.getpid()).memory_info()
print(f"{durations_s_sum:4.1f}s for 50 pickle files, rss={memory_info.rss/1024/1024:6,.0f}MB, vms={memory_info.vms/1024/1024:6,.0f}MB")
durations_s_sum = 0.
num_image_sets = 0
Windows 11
# Versions: platform.system()='Windows', platform.release()='10', platform.version()='10.0.22631', sys.version='3.11.5 | packaged by Anaconda, Inc. | (main, Sep 11 2023, 13:26:23) [MSC v.1916 64 bit (AMD64)]', np.__version__='1.26.3'
# 11.7s for 50 pickle files, rss= 1,211MB, vms= 1,215MB
# 11.8s for 50 pickle files, rss= 1,492MB, vms= 1,499MB
# 13.8s for 50 pickle files, rss= 2,272MB, vms= 2,302MB
# 15.7s for 50 pickle files, rss= 2,802MB, vms= 2,845MB
# 18.3s for 50 pickle files, rss= 3,328MB, vms= 3,383MB
# 21.0s for 50 pickle files, rss= 3,837MB, vms= 3,905MB
# 25.6s for 50 pickle files, rss= 4,369MB, vms= 4,448MB
# 28.0s for 50 pickle files, rss= 4,898MB, vms= 4,989MB
# 32.3s for 50 pickle files, rss= 5,427MB, vms= 5,530MB
# 36.7s for 50 pickle files, rss= 5,966MB, vms= 6,081MB
Linux
# Versions: platform.system()='Linux', platform.release()='6.0.12-76060012-generic', platform.version()='#202212290932~1674066459~20.04~3cd2bf3-Ubuntu SMP PREEMPT_DYNAMI', sys.version='3.10.9 (main, Jan 11 2023, 15:21:40) [GCC 11.2.0]', np.__version__='1.23.5'
# 2.8s for 50 pickle files, rss= 1,222MB, vms= 2,229MB
# 2.8s for 50 pickle files, rss= 1,730MB, vms= 2,738MB
# 2.8s for 50 pickle files, rss= 2,238MB, vms= 3,246MB
# 2.8s for 50 pickle files, rss= 2,747MB, vms= 3,754MB
# 2.8s for 50 pickle files, rss= 3,255MB, vms= 4,263MB
# 2.8s for 50 pickle files, rss= 3,764MB, vms= 4,772MB
# 2.8s for 50 pickle files, rss= 4,272MB, vms= 5,280MB
# 2.8s for 50 pickle files, rss= 4,780MB, vms= 5,789MB
# 2.9s for 50 pickle files, rss= 5,288MB, vms= 6,298MB
# 2.9s for 50 pickle files, rss= 5,797MB, vms= 6,806MB
CPython versions tested on:
3.11
Operating systems tested on:
Windows
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
The issue names no repository files or tests; start by running the supplied pickle.load() reproducer on Windows and Linux with the reported versions, while monitoring timing and memory usage. Done means explaining the progressive Windows slowdown and addressing it with regression coverage.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- numpy, python
- Domain
- operating-systems, performance
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 35/100