Messages in this thread | | | From | Wolfgang Wander <> | Date | Fri, 15 Apr 2005 17:54:38 -0400 | Subject | Re: Leaks in mmap address space: 2.6.11.4 |
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Here is another program that illustrates the problem which this time in C and without using glibc allocation schemes.
---------------------------------------------------------------------- /* run in 32 bit mode on 64Bit kernel, >4GB of RAM is helpful */
#include <stdio.h> #include <string.h> #include <unistd.h> #include <sys/mman.h>
#define bsz 600 /* number of mmaps to keep */ #define large 9500000 /* some odd large number */ #define success 1000000 /* number of iterations before we believe we are ok*/
/* program fails here on 2.6.11.4 kernel after 52K iterations with a fragmented /proc/self/mmap, 2.4 kernels behave fine */ void aLLocator() {
char* bvec[bsz]; unsigned int i; memset( bvec,0,sizeof(bvec)); for( i = 0; i < success ; ++i ) { unsigned oidx; unsigned kidx; int len; kidx = i % bsz; oidx = (i+bsz/10) % bsz; len = (oidx & 7) ? ((oidx&7)* 1048576) : large; if( bvec[oidx] ) { munmap( bvec[oidx], len ); bvec[oidx] = 0; } len = (kidx & 7) ? ((kidx&7)* 1048576) : large; bvec[kidx] = (char*)(mmap(0, len, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)); if( bvec[kidx] == (char*)(-1) ) { printf("Failed after %d rounds\n", i); break; } } }
int main() { FILE *f; int c;
aLLocator();
f = fopen( "/proc/self/maps", "r" ); while( (c = fgetc(f)) != EOF ) putchar(c); fclose(f); return 0; } ----------------------------------------------------------------------
Wolfgang Wander writes: > Hi, > > we are running some pretty large applications in 32bit mode on 64bit > AMD kernels (8GB Ram, Dual AMD64 CPUs, SMP). Kernel is 2.6.11.4 or > 2.4.21. > > Some of these applications run consistently out of memory but only > on 2.6 machines. In fact large memory allocations that libc answers > with private mmaps seem to contribute to the problem: 2.4 kernels > are able to combine these mmaps to large chunks whereas 2.6 > generates a rather fragmented /proc/self/maps table. > > The following C++ program reproduces the error (compiled statically > on a 32bit machine to get exactly the same executable for 2.4 and > 2.6 environments): - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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