Hello,
I've encountered a big slowdown in our .NET application (the Nemerle
compiler) running on mono after -DUSE_MMAP and -DUSE_MUNMAP was
enabled. The ``big'' translates to 2x slowdown in GC_mark_from (which results
in about 10% slowdown of the entire application).
After some investigation I've managed to create a simple C testcase
(as lupus suggested). It seems that -DUSE_MUNMAP makes garbage collection
to be called twice as many times, -DUSE_MMAP
doesn't seem to affect that. The question is: is it normal? How can it
be avoided?
I tested the C program on amd64 and x86.
The Nemerle compiler exhibits better memory behavior with -DUSE_MMAP
(by about 2%) and further better memory behavior with -DUSE_MUNMAP
(by about 10%). The C test program doesn't seem to exhibit this though
(probably because of lack of false positives and large allocations).
Here's the test C program:
#v+
#include "include/gc.h"
#include <stdio.h>
typedef struct _tree_node {
struct _tree_node *left;
struct _tree_node *right;
long d1, d2, d3;
long d4, d5, d6;
} tree_node;
int bytes_allocated;
int counter;
tree_node *alloc(int depth)
{
tree_node *n;
int size;
if (depth < 0)
return NULL;
// make some garbage
if (counter++ % 3 == 0)
alloc(depth - 1);
size = sizeof (tree_node);
bytes_allocated += size + sizeof(void*);
n = GC_malloc (size);
n->left = alloc (depth - 1);
n->right = alloc (depth - 1);
return n;
}
int main ()
{
tree_node *n = alloc (19);
printf ("%.3fM %.3fM %ld %p\n", bytes_allocated / (1024.0*1024.0),
GC_get_heap_size () / (1024.0*1024.0),GC_gc_no, n);
return 0;
}
#v-
--
Michal Moskal,
http://nemerle.org/~malekith/
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