Interesting. I cannot reproduce the malloc() problem. I have no issues
running your example with uncommented malloc:
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
int main()
{
size_t size = 512 * 1024 * 1024;
printf("Hello from main\n");
printf("allocation %lx start\n", size);
int *p = (int *)malloc(size); // FAIL
//int *p = (int *)mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE |
MAP_ANONYMOUS, -1, 0); // OK
printf("allocation %lx = %p\n", size, p);
*(p) = 512;
printf("access done\n");
return 0;
}
OSv v0.53.0-107-g4f59f284
eth0: 192.168.122.15
Booted up in 135.90 ms
Cmdline: /test_large --help
Hello from main
allocation 20000000 start
allocation 20000000 = 0xffff800001b0d040
access done
As you can see the address returned is a virtual one. Can you email your
thread stack trace when it crashes in your case?
As far as why we commit the memory for all malloc I can not answer this and
others might be able to address why it was designed like this.
This might be a relevant issue -
https://github.com/cloudius-systems/osv/issues/854. I guess we might change
implementation of malloc_large() and for large sizes create a VMA like for
mmap. But then malloc is used all over the place in kernel code so I wonder
if we would not have issues like nested faults - see this -
https://github.com/cloudius-systems/osv/issues/143 - it has some background
between malloc() and mmap() handling in OSv.
Waldek
On Monday, September 9, 2019 at 7:41:31 AM UTC-4, pusno...@gmail.com wrote:
>
> Hi,
> I found malloc returns physical address in mempool area and does not
> perform demand paging (only mmap does).
> Is there any reason for the design choice?
> OSv fails, even if it only uses small portion of allocated memory.
>
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <sys/mman.h>
>
> int main()
> {
> size_t size = 512 * 1024 * 1024;
> printf("Hello from main\n");
> printf("allocation %x start\n", size);
> //int *p = (int *)malloc(size); // FAIL
> int *p = (int *)mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_PRIVATE |
> MAP_ANONYMOUS, -1, 0); // OK
> printf("allocation %x = %p\n", size, p);
> *(p) = 512;
> printf("access done\n");
>
> return 0;
> }
>
>
> Thanks.
>
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