I was reminded about the patch I wrote for Igor Sysoev some time ago. The issue the patch tries to handle is that jemalloc uses mmap() instead of sbrk() for pages allocation, and thus RLIMIT_DATA limit is no longer effective to put the bounds on the process heap. Since reverting to sbrk for such purpose is worse then the issue itself, I proposed a solution of 'self-restricting malloc'.
The patch adds a flag MAP_DATALIMIT to the flags argument of mmap(2), which instructs the system to account the mapping in the RLIMIT_DATA resource count. The malloc(3) also gets new option 'L' to enable passing MAP_DATALIMIT to mmap() when allocating pages. By default, the 'L' option is not activated. Now, if user wants to ensure that process heap is restricted by the ulimit -d and still use mmap() for jemalloc, he supplies the option using any mechanism. The behaviour is voluntaristic, to prevent the trashing use RLIMIT_SWAP. Do people consider the facility useful ? Any comments for the patch itself ? http://people.freebsd.org/~kib/misc/map_datalimit.1.patch
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