Stefan Lankes wrote:
> I am not able to reconstruct any performance drawbacks on my system.
> Could you send me your low-level benchmark?
It's attached. As you may see, it's fairly trivial. It just does several
iterations of mbind+touch_all_pages for different power-of-two buffer
sizes. Just replace mbind with madvise in the inner loop if you want to
try with your affinit-on-next-touch.
Which kernels are you using when comparing your next-touch
implementation with Lee's patchset?
Brice
#define _GNU_SOURCE 1
#include <unistd.h>
#include <sys/mman.h>
#include <sys/time.h>
#include <stdio.h>
#include <stdlib.h>
#include <numa.h>
#include <numaif.h>
#include <errno.h>
#include <sched.h>
#ifndef MPOL_MF_LAZY
#define MPOL_MF_LAZY (1<<3)
#endif
#define TOTALPAGES 262144
int nbpages, loop;
int pagesize;
int main(int argc, char **argv) {
void *buffer;
int i, err;
unsigned long nodemask;
int maxnode;
struct timeval tv1, tv2;
unsigned long us;
cpu_set_t cset;
/* put the thread on node 0 */
CPU_ZERO(&cset);
CPU_SET(0, &cset);
err = sched_setaffinity(0, sizeof(cset), &cset);
if (err < 0) {
perror("sched_setaffinity");
exit(-1);
}
pagesize = getpagesize();
maxnode = numa_max_node();
fprintf(stdout, "# Nb_pages\tCost(ns)\n");
for(nbpages=2 ; nbpages<=TOTALPAGES ; nbpages*=2) {
int loops = TOTALPAGES/nbpages;
if (loops > 128) loops = 128;
buffer = mmap(NULL, TOTALPAGES*pagesize, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
if (buffer == MAP_FAILED) {
perror("mmap");
exit(-1);
}
/* bind to node 1 and prefault */
nodemask = 1<<1;
err = mbind(buffer, TOTALPAGES*pagesize, MPOL_BIND, &nodemask, maxnode+2, MPOL_MF_MOVE);
if (err < 0) {
perror("mbind");
exit(-1);
}
for(i=0 ; i<TOTALPAGES ; i++)
*(int*)(buffer+i*pagesize) = 0;
gettimeofday(&tv1, NULL);
for(loop=0 ; loop<loops ; loop++) {
/* mark subbuf as next-touch and touch it */
void *subbuf = buffer + loop*nbpages*pagesize;
err = mbind(subbuf, nbpages*pagesize, MPOL_PREFERRED, NULL, 0, MPOL_MF_MOVE|MPOL_MF_LAZY);
if (err < 0) {
perror("mbind");
exit(-1);
}
for(i=0;i<nbpages;i++)
*(int*)(subbuf + i*pagesize) = 42;
}
gettimeofday(&tv2, NULL);
us = (tv2.tv_sec - tv1.tv_sec) * 1000000 + (tv2.tv_usec - tv1.tv_usec);
fprintf(stdout, "%d\t%ld\n", nbpages, us * 1000/loops);
fflush(stdout);
munmap(buffer, TOTALPAGES*pagesize);
}
return 0;
}
