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One of the folks I'm working with found this. The following code,
which yes, is just an example, is 1/2 as fast on 7.0-RELEASE as on
6.3. Where should I look to find out why?


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culprit continues to be arena_run_malloc, which takes several times longer
on fbsd7 than the total of all calls to *alloc* on fbsd6.

Output of uname -a:
FreeBSD testlab5 7.0-STABLE FreeBSD 7.0-STABLE #1: Thu Feb 28 10:06:47 EST
2008 root@builder:/usr/obj/usr/sources/FreeBSD.7/src/sys/GENERIC amd64

Program source:
// simple test program that shows fbsd7 memory operations 2x slower than
// compile with:
// g++ -o memory.o -c -O3 -Wall memory.cc
// g++ -o memory memory.o -O3 -L/usr/local/lib

class MemUser {
void nTimesInOrder(int n) { for (int i=0; i freeInOrder(); } }
void alloc();
void freeInOrder();
void freeRandom();

char* p;
char* ptrs[16384];
int psize;

void MemUser::alloc()
int n = 0;
// for now, allocating 1000 times at each size. Sizes are 2, 20, 200,
2000, 20k, 200k bytes
for (int size=2; size <= 2e5; size *= 10) {
for (int i=0; i<1000; ++i) {
p = new char [size];
ptrs[n++] = p;
psize = n;

void MemUser::freeInOrder()
for (int i=0; i < psize; ++i) {
delete [] ptrs[i];

int main(int argc, char* argv[])
MemUser mu;

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