The problem occurs for example with any program which was compiled with the address sanitizer.
A simple hello program compiled with "gcc -fsanitize=address hello.c" is sufficient to show the problem. Just run it with "qemu-x86_64 a.out". It will be killed by the Linux kernel OOM handler even on a server with 64 GB RAM. -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1898011 Title: mmap MAP_NORESERVE of 2^42 bytes consumes 16Gb of actual RAM Status in QEMU: Confirmed Bug description: Run this program: #include <sys/mman.h> #include <stdio.h> int main() { for (int i = 30; i <= 44; i++) { fprintf(stderr, "trying 2**%d\n", i); mmap((void*)0x600000000000,1ULL << i, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED|MAP_NORESERVE,-1,0); } } (tried qemu-x86_64 and qemu-aarch64, 4.2.1 and trunk/5.1.50) On each iteration qemu will consume 2x more physical RAM, e.g. when mapping 2^42 it will have RSS of 16Gb. On normal linux it works w/o consuming much RAM, due to MAP_NORESERVE. Also: qemu -strace prints 0 instead of the correct size starting from size=2^32 and prints -2147483648 for size=2^31. mmap(0x0000600000000000,1073741824,PROT_NONE,MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED|MAP_NORESERVE,-1,0) = 0x0000600000000000 mmap(0x0000600000000000,-2147483648,PROT_NONE,MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED|MAP_NORESERVE,-1,0) = 0x0000600000000000 mmap(0x0000600000000000,0,PROT_NONE,MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED|MAP_NORESERVE,-1,0) = 0x0000600000000000 To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1898011/+subscriptions
