[Python-ideas] Porting os.fork to Windows?
sturla at molden.no
Wed Feb 18 11:11:37 CET 2009
On 2/17/2009 11:28 PM, Christian Heimes wrote:
> The code implements fork() on top of the NT API, not the Win32 API.
The tcsh code implements fork on top of the Win32 API like Cygwin.
> fork() is an efficient and fast op on Unix systems like Linux and BSD,
> because it uses a technique called copy on write (cow). I couldn't
> find any information if NT uses cow, too.
NT's fork (in the SUA subsystem on Vista) is copy-on-write optimized. It
uses ZwCreateProcess in ntdll.dll to produce a copy-on-write clone of a
process. But that is besides the point.
The fork() in tcsh does not do copy-on-write optimization, not does
Cygwin's fork(). There is nothing that mandates that fork() must be
implemented with copy-on-write. The raison d'etre for pthreads was the
non-cow fork() implementation in Solaris. Linux originally had a non-cow
fork too. Albeit slower, this version of fork is still useful.
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