diff options
Diffstat (limited to 'results/scraper/launchpad-without-comments/1898011')
| -rw-r--r-- | results/scraper/launchpad-without-comments/1898011 | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/results/scraper/launchpad-without-comments/1898011 b/results/scraper/launchpad-without-comments/1898011 new file mode 100644 index 00000000..6b4328d7 --- /dev/null +++ b/results/scraper/launchpad-without-comments/1898011 @@ -0,0 +1,30 @@ +mmap MAP_NORESERVE of 2^42 bytes consumes 16Gb of actual RAM + +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 \ No newline at end of file |