多进程加协程爬虫问题

我想用 mutiprocess 和 gevent，requests 配合来爬取拉钩上面的关于各种语言的职位信息，思路就是每种语言开一个进程，比如 java 有 30 页职位信息，我就在 java 进程用 gevent 开 30 个协程去爬每 30 个页面职位信息，可是当我爬的时候发现进程数开多了之后， 多进程加协程却没有单纯的多进程爬取速度快，且随着进程数开启的越多，会有更多的页面 timeout，爬取失败。但单纯的多进程却始终维持在 34s 左右，且基本都爬下所有的页面。下面是我测试的数据：

一个进程+多协程 12s

一个进程 34s

两个进程+多协程 26s

两个进程 34s

三个进程+多协程 51s

三个进程 34s

下面是我的主要代码，请问是我的进程和协程的使用姿势不对还是有什么问题吗，为什么在进程数开多了之后协程反而会拖慢爬虫的效率呢，第一次提问，如有不对之处请多多见谅，谢谢各位。

def get_profession_jobs(self, professions):

    process = []
    for profession in professions:
        p = Process(target=self.get_all_pages, args=(profession, self.page_list))
        p.start()
        process.append(p)
    for p in process:
        p.join()

def get_all_pages(self, profession, pages):

    print(os.getpid())
    jobs = [gevent.spawn(self.get_detail_page, profession, page) for page in pages]
    gevent.joinall(jobs)
    #for page in pages:
        #self.get_detail_page(profession, page)

def get_detail_page(self, profession, page):

    user_agent = self.user_agents[random.randint(0, 3)]
    header = {
                'Host': 'www.lagou.com',
                'Referer': self.base_referer + profession,
                'User-Agent': user_agent,
                'Origin': 'https://www.lagou.com',
                'Accept-Encoding': 'gzip, deflate, br',
                'Accept-Language': 'zh-CN,zh;q=0.9',
                'Accept': 'application/json, text/javascript, */*; q=0.01',
                'Content-Type': 'application/x-www-form-urlencoded; charset=UTF-8' }

    data = {'pn': page, 'kd': profession}
    print(profession + ' page ' + str(page) + ' start')
    response = requests.post(self.base_url, headers=header, data=data, timeout=20)
    self.clear_data(response.content, profession)
    print(profession + ' page ' + str(page) + ' finished')

def clear_data(self, page, profession):

    results = json.loads(page.decode('utf-8'))['content']['positionResult']['result']
    for result in results:
        job_name = result['positionName']
        job_class = profession
        publish_date = result['createTime']
        money = result['salary']
        experience = result['workYear']
        education = result['education']
        location = result['city']

        with open('jobs.csv', 'a', newline='') as jobs:
            writer = csv.writer(jobs)
            writer.writerow([job_name, job_class, publish_date, money, experience, education, location])

if name == 'main':

start_time = time.time()
professions = ['PHP', 'Python', 'Go', 'Java']
spider = Spider()
spider.get_profession_jobs(professions)
end_time = time.time()
print('All finished')
print('Used ' + str(end_time-start_time) + ' seconds')