On 6/23/26 09:58, Hongru Zhang wrote:

quoted

On 5/20/26 23:15, Matthew Wilcox wrote:

quoted

all of the applications i run are either single threaded or don't fork.
what multithreaded applications call fork?

Traditionally the problem was random libraries using fork+execve to launch other
programs ... instead of using alternatives like posix_spwan (some use cases
require more work done before execve and cannot yet switch to that). I'd hope
that that is less of a problem on Android.

I assume Android zygote might be multi threaded? Maybe sshd as well? Systemd?
But I'd be surprised if there are really performance implications.

Not sure about webbroswers .... I think most of them switched to fork servers,
where I would assume fork servers would be single-threaded.

So, yeah, getting a clear understanding how this ends up being a problem on
Android would be great.

Barry asked me to share observations on fork() usage across Android
applications.

I wrote a BPF-based tracing tool (kprobe on copy_process, checking
CLONE_VM to distinguish process creation from thread creation) and ran
it against the top 200 Android applications in the China market during
normal usage scenarios.

Results:
- 82 out of 200 apps (41%) call fork() during normal operation

Crazy. Thanks for these numbers.

- Among these, some call fork() from multiple threads

These are not zygote forks — they are fork() calls initiated by app
threads at runtime. Examples by category:

  Browsers:     com.quark.browser, com.UCMobile, com.xunlei.browser
  Shopping:     com.taobao.taobao, com.tmall.wireless, com.achievo.vipshop
  Video:        com.youku.phone, com.qiyi.video, com.hunantv.imgo.activity
  Social/IM:    com.alibaba.android.rimet, com.ss.android.lark
  News:         com.ss.android.article.news, com.ss.android.article.lite
  Navigation:   com.autonavi.minimap, com.sdu.didi.psnger
  Finance:      com.eg.android.AlipayGphone, com.chinamworld.main

I know that especially browser usually use fork servers: a tiny
(single-threaded) process just to create new child processes. Any information
regarding the apps above that use fork() on small vs. large processes?

This confirms that fork() is widely used in real-world multi-threaded
Android applications.

Above you write "some call fork() from multiple threads". Any further
information on that?

-- 
Cheers,

David