Re: fork and COW

[Jaromír Doleček <jaromir.dolecek%gmail.com@localhost>]

Le lun. 29 juin 2020 à 21:18, Dima Veselov <kab00m%lich.phys.spbu.ru@localhost> a écrit :
> I know running binary on image upload is a bad idea, but I wonder
> why in our testing environment on Linux it does not happen. My thought
> was somewhere around COW capabilities of fork() but as I know COW is
> implemented in NetBSD as well. Is it true and it should work same as on
> Linux or there might be some differences?

Yes, it works the same.

However COW is only relevant before php-fpm does exec of ImageMagick.
Immediately after fork the child shares the address space with the
parent having the memory pages marked as COW, after exec the child no
longer shares the virtual address space with the parent. There is
never any address space sharing for the independently executed
ImageMagick processes.

It's likely Something Else (tm).

Does php-imagick support what you need to do? That way you'd avoid
executing external binaries.

Jaromir