[cpeterso]

djb's allocator alloc() does this. He preallocates a 4 KB static buffer before hitting system malloc(). Avoiding the overhead of malloc() is pretty important for the performance of systems like qmail that fork many small processes.

[tedunangst]

That's ridiculous. The overhead of fork is about a bajillion times higher than malloc.

[adestefan]

With a COW fork() I bet it's smaller. I smell a test coming on, but alas it's late here and I'm going to bed.

I'm also guessing that 4k was chosen because a malloc() of 1 page is faster than a malloc() of >1 page. Of course that's with the assumption that the systems use a 4k page size.

[aidenn0]

Are you sure? I'd bet it's greater, I'd not bet that it's an order of magnitude better, fork() has been optimized a lot more than brk().

[sliverstorm]

Many small processes? How many?

4 KB * (many) could be frightening.

[jff]

If your system has 32,000 processes and you allocate 4 KB to each of them... that's 128 MB. I'm not crapping my pants at that figure because even the oldest machine in my office, an old Thinkpad, has 2 GB of RAM.