> For the complete documentation index, see [llms.txt](https://book.bsdcn.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://book.bsdcn.org/man/man9/hardclock.9.md).

# hardclock.9

`hardclock` — 实时时钟

## 名称

`hardclock`

## 概要

```c
void
hardclock(int cnt, int usermode)
```

## 描述

`hardclock` 函数根据挂起的工作周期性调用。频率范围从非常繁忙系统的每秒 `hz` 次到空闲系统的每秒两次。`cnt` 参数报告自上次调用以来的 tick 数估计。在较长时间尺度上，每秒 `cnt` 的平均总和为 `hz`。有关较短时间尺度的重要细节，请参见 [hz(9)](/man/man9/hz.9.md)。当 `hardclock` 从中断用户模式执行的上下文中调用时，`usermode` 参数为非零。

`hardclock` 可执行不同的任务，例如：

* 运行当前进程的虚拟时间和配置文件时间（如果激活，则递减相应的计时器，并分别生成 `SIGVTALRM` 或 `SIGPROF`）。
* 递增一天中的时间，处理任何 ntpd(8) 或 adjtime(2) 引起的更改和闰秒，以及与 PPS 信号或外部时钟保持同步所需的任何补偿（如果内核支持）。
* 调度 softclock 中断（[swi(9)](/man/man9/swi.9.md)）处理。
* 收集 [hwpmc(4)](/man/man4/hwpmc.4.md) 统计信息。
* 启用时执行设备轮询（参见 [polling(4)](/man/man4/polling.4.md)）。
* 实现软件 [watchdog(9)](/man/man9/watchdog.9.md) 处理。
* 入队 [epoch(9)](/man/man9/epoch.9.md) 处理。

## 参见

`adjtime(2)`, `ntp_adjtime(2)`, `signal(3)`, [hwpmc(4)](/man/man4/hwpmc.4.md), [polling(4)](/man/man4/polling.4.md), `ntpd(8)`, [epoch(9)](/man/man9/epoch.9.md), [eventtimers(9)](/man/man9/eventtimers.9.md), [hz(9)](/man/man9/hz.9.md), [swi(9)](/man/man9/swi.9.md), [watchdog(9)](/man/man9/watchdog.9.md)


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://book.bsdcn.org/man/man9/hardclock.9.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.