Re: [perf-discuss] Syscall for posix_spawn?

[Phil Harman]

I was merely saying we need a spawn() equivalent to fork()/exec() which 
doesn't suffer the "stop all LWPs" limitation of vfork(). It would 
certainly make sense for such a syscall to support a faster 
implementations of posix_spawn(3), but the latter doesn't have to be a 
syscall per se.

Phil
p.s. I hadn't noticed that Roger was on the Cc list when I replied. I'd 
just like to make to clear that Roger could never be accused of an 
ETOOHARD response to any challenge. Indeed, it is Roger we have to thank 
for so many things (e.g. unified process model) that others considered 
ETOOHARD!

On 12/07/2010 13:05, ольга крыжановская wrote:
I don't want spawn(2), I want posix_spawn(2). The last is more
powerful and would reduce the number of system calls, possibilities
for race conditions and execute faster than the bla(), bla(), bla(),
bla(), bla(), bla(), bla(), bla(), bla(), bla(), bla(), bla(), bla(),
bla(), bla(), bla(), bla(), bla(), bla(), bla(), bla(), bla(), bla(),
bla(), bla(), bla(), bla(), bla(), bla(), bla(), bla(), bla(), bla(),
bla(), bla(), bla(), bla(), bla(), bla(), bla(), bla(), bla(), bla(),
bla(), bla(), bla(), bla(), bla(), bla(), bla(), bla(), bla(),
vfork(), exec() applications and shells have to use today.

Olga

2010/7/12 Phil Harman<phil.har...@gmail.com>:
   
This was one of my pet peeves during my 20 years at Sun. The main reason I wanted spawn(2) was for 
multithreaded apps needing to start new processes. The issue was that all LWPs need to be quiesced 
before even a vfork(2), which meant that something as simple as just calling system(3) might stop 
the world. The standard response from the gurus was ETOOHARD, followed by a good dose of FUD about 
how fundamental fork/exec was to UNIX, and that we couldn't be sure a spawned process would be 
exactly the same, "think of all the implicit inheritance". The proposed workaround was 
always the same: "your multithreaded app should use a fork helper co-process to do its 
spawning for it".

I salute you and wish you well!

On 12 Jul 2010, at 04:46, ольга крыжановская<olga.kryzhanov...@gmail.com>  
wrote:

     
Perf team, has any one been interested in implementing posix_spawn()
as system call to improve performance? posix_spawn() is implemented as
sequence of vforkx and execve currently with many intermediate system
calls around it. From by looking at it and the kernel code of vforkx
and execve it might be beneficial to turn the whole thing into one
single system call.

Olga
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