First of all, malloc implementations that rely on brk are simply broken. The whole idea of a process-wide data segment is broken and leads not only to awkwardness around thread safety safety, also the inability to decommit memory when it's no longer needed. Decent malloc implementations use mmap.
Second, the whole idea that a page isn't really "allocated" until you touch it is just stupid, lazy, and terrible; it doesn't exist on sane operating systems like NT. On decent systems, mmap (or its equivalent) sets aside committed memory and malloc carves out pieces from that block.
It's frustrating to see people who grew up with Linux not only understand how terrible and broken Linux's memory management is, but not realizing that it could be any other way.
NT doesn't have fork. Supporting that requires copy-on-write semantics. And you don't want to stop fork just because you don't have enough memory for a second complete copy of the current processes; you might be about to throw all that away with an exec, and even if not you're likely to keep most of the shared memory shared.
Well, first of NT is... different. Not sure if it's sane or superior or whatever.
Second, you may be right that this behavior causes problems, but it clearly has advantages as well. You advocate copy-on-write semantics elsewhere. Well this behavior is basically that.
Third, dlmalloc() which is pretty widely used, uses sbrk().
Forth, I sense a whole lot of frustration targeted at "these damn Linux kids". Sorry you feel that way. On the plus side, it's Friday, and this particular Linux kid would gladly buy you a beer to help cheer you up.
(Technically, I grew up with NetBSD, not Linux. Wrote a toy allocator for it at one point, and am trying to work on one that works for Linux as well.)
Second, the whole idea that a page isn't really "allocated" until you touch it is just stupid, lazy, and terrible; it doesn't exist on sane operating systems like NT. On decent systems, mmap (or its equivalent) sets aside committed memory and malloc carves out pieces from that block.
It's frustrating to see people who grew up with Linux not only understand how terrible and broken Linux's memory management is, but not realizing that it could be any other way.