fork and COW

[Dima Veselov <kab00m%lich.phys.spbu.ru@localhost>]

Greetings,

I have some problems with my php-fpm web-server backends which occur on
image upload. I found php-fpm forking and running ImageMagick's convert
as much times as much pictures one try to upload. Uploading 10 pictures
at once will make the daemon fork 10 times, 512M each and memory is easily
exhausted. 

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?

--
Sincerely yours,
Dima Veselov
Physics R&D Establishment of Saint-Petersburg University