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SubjectRe: mprotect() failed: Cannot allocate memory
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Le mercredi 21 avril 2010 à 01:44 +0200, Paweł Sikora a écrit :
> On Wednesday 21 April 2010 01:17:22 Mike Frysinger wrote:
> > On Tuesday 20 April 2010 19:05:20 Paweł Sikora wrote:
> > > i'm trying to debug an ugly application with ElectricFence.
> >
> > electricfence does a lot of ugly memory tricks to do its thing, including,
> > but not limited to, overriding memory related symbols. best to seek help
> > from the electricfence authors.
>
> so, let's avoid EF and run following test:
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <unistd.h>
> #include <sys/mman.h>
>
> void* my_alloc( size_t n )
> {
> size_t ps = getpagesize();
> printf( "request for %Zd bytes => ", n );
> /* alloc PAGE_SIZE + n */
> char* p = mmap( 0, ps + n, PROT_READ | PROT_WRITE, MAP_SHARED |
> MAP_ANONYMOUS, -1, 0 );
> if ( p == MAP_FAILED )
> __builtin_abort();
> /* block guard page */
> int rc = mprotect( p, ps, PROT_NONE );
> if ( rc != 0 )
> __builtin_abort();
> char* q = p + ps;
> printf( "guard page @ %p, allocated region @ %p\n", p, q );
> return q;
> }
>
> int main()
> {
> #define N 100
> size_t NN = 4*100*100;
> size_t kmax = 100;
> int i;
>
> double **bm = (double **)my_alloc( NN * sizeof( double* ) );
> for( i = 0; i < NN; ++i )
> {
> bm[ i ] = (double*)my_alloc( kmax * sizeof( double ) );
> }
> // leak...
> return 0;
> }
>
> and the result is...
>
> (...)
> mmap(NULL, 4896, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, 0) =
> 0x7f5fd97df000
> mprotect(0x7f5fd97df000, 4096, PROT_NONE) = -1 ENOMEM (Cannot allocate memory)

Have you checked available memory on your system ? Or user limit ?

You test program is going to allocate
79 + 1 pages for bm
1 + 1 for each double arrays (x 40000)
So in the end your program is allocating 80080 pages, so about
312MBytes.

It not that big for a 64bits system.

Check limits such as
-d the maximum size of a process's data segment
-l the maximum size a process may lock into memory
-m the maximum resident set size

Regards.

--
Yann Droneaud


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