enomem

As the parent process is using huge mount of memory, fork may fail with errno of ENOMEM under some configuration of kernel overcommit policy. Even though the child process may only exec low memory-consuming program like ls. To clarify the problem, when /proc/sys/vm/overcommit_memory is configured to be 2, allocation of (virtual) memory is limited to SWAP + MEMORY * ration(default to 50%) . When a process forks, virtual memory is not copied thanks to COW. But the kernel still need to allocate virtual memory space. As an analogy, fork is like malloc(virtual memory space size) which will not

I have a situation in which malloc() returns NULL and sets errno to ENOMEM . But the CRT heap (which is growable) has plenty of memory to work with. At the time of malloc , my process memory is about 900 MB. The host process is a Java executable executed under the Sun HotSpot JVM. The malloc() I'm doing is 80 megabytes, and fails. If I do a 60 MB allocation, it succeeds. After that, a 50 MB allocation, followed by another one, and another one also succeed : clearly, I still have a lot of memory left but the 80 MB malloc seems too "big" to digest for the OS. I'm using Windows 7 x64 SP1 with 4

I have recently discovered that Linux does not guarantee that memory allocated with mmap can be freed with munmap if this leads to situation when number of VMA (Virtual Memory Area) structures exceed vm.max_map_count . Manpage states this (almost) clearly: ENOMEM The process's maximum number of mappings would have been exceeded. This error can also occur for munmap(), when unmapping a region in the middle of an existing mapping, since this results in two smaller mappings on either side of the region being unmapped. The problem is that Linux kernel always tries to merge VMA structures if