Re: mprotect() failed: Cannot allocate memory

[PaweÅ Sikora]

Dnia 21-04-2010 o 11:22:19 Yann Droneaud <yann@xxxxxxxxxxx> napisaÅ(a):

> Le mercredi 21 avril 2010 Ã 01:44 +0200, PaweÅ Sikora a Ãcrit :
> > On Wednesday 21 April 2010 01:17:22 Mike Frysinger wrote:
> > > On Tuesday 20 April 2010 19:05:20 PaweÅ 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

$ ulimit -a
-t: cpu time (seconds)         unlimited
-f: file size (blocks)         unlimited
-d: data seg size (kbytes)     unlimited
-s: stack size (kbytes)        8192
-c: core file size (blocks)    0
-m: resident set size (kbytes) unlimited
-u: processes                  unlimited
-n: file descriptors           1024
-l: locked-in-memory size (kb) 64
-v: address space (kb)         unlimited
-x: file locks                 unlimited
-i: pending signals            64024
-q: bytes in POSIX msg queues  819200
-e: max nice                   0
-r: max rt priority            0

$ free -m
             total       used       free     shared    buffers     cached
Mem:          8004       1779       6224          0         36       1228
-/+ buffers/cache:        514       7489
Swap:        15625          0      15625


imho the testcase has enough hardware resources.
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