papi_l2_dcm.c

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/* This code attempts to test the L2 Data Cache Missses     */
/* performance counter PAPI_L2_DCM              */

/* by Vince Weaver, vincent.weaver@maine.edu            */


/* Due to prefetching it is hard to create a testcase short of */
/* just having random accesses. */
/* In addition, due to context switching the cache might be */
/* affected by other processes on a busy system. */

/* Other tests to attempt */
/* Repeatedly reading same cache line should give very small error */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include "papi.h"
#include "papi_test.h"

#include "cache_helper.h"
#include "display_error.h"

#include "testcode.h"

/* How much should we allow? */
#define ALLOWED_ERROR   5.0

#define NUM_RUNS    100

#define ITERATIONS  1000000

int main(int argc, char **argv) {

    int i;
    int eventset=PAPI_NULL;
    int num_runs=NUM_RUNS;
    long long high,low,average,expected;
    long long count,total;

    int retval;
    int l1_size,l2_size,l1_linesize,l2_linesize,l2_entries;
    int arraysize;
    int quiet,errors=0;

    double error;
    double *array;
    double aSumm = 0.0;

    quiet=tests_quiet(argc,argv);

    if (!quiet) {
        printf("Testing the PAPI_L2_DCM event\n");
    }

    /* Init the PAPI library */
    retval = PAPI_library_init(PAPI_VER_CURRENT);
    if (retval != PAPI_VER_CURRENT) {
        test_fail(__FILE__,__LINE__,"PAPI_library_init",retval);
    }

    retval=PAPI_create_eventset(&eventset);
    if (retval!=PAPI_OK) {
        test_fail( __FILE__, __LINE__, "PAPI_create_eventset", retval );
    }

    retval=PAPI_add_named_event(eventset,"PAPI_L2_DCM");
    if (retval!=PAPI_OK) {
        test_skip( __FILE__, __LINE__, "adding PAPI_L2_DCM", retval );
    }

    l1_size=get_cachesize(L1D_CACHE);
    l1_linesize=get_linesize(L1D_CACHE);
    l2_size=get_cachesize(L2_CACHE);
    l2_linesize=get_linesize(L2_CACHE);
    l2_entries=get_entries(L2_CACHE);

    if (!quiet) {
        printf("\tDetected %dk L1 DCache, %dB linesize\n",
            l1_size/1024,l1_linesize);
        printf("\tDetected %dk L2 DCache, %dB linesize, %d entries\n",
            l2_size/1024,l2_linesize,l2_entries);
    }

    arraysize=(l2_size/sizeof(double))*8;

    if (arraysize==0) {
        if (!quiet) printf("Could not detect cache size\n");
        test_skip(__FILE__,__LINE__,"Could not detect cache size",0);
    }

    if (!quiet) {
        printf("\tAllocating %zu bytes of memory (%d doubles)\n",
            arraysize*sizeof(double),arraysize);
    }

    array=calloc(arraysize,sizeof(double));
    if (array==NULL) {
        test_fail(__FILE__,__LINE__,"Can't allocate memory",0);
    }

    /******************/
    /* Testing Writes */
    /******************/

    if (!quiet) {
        printf("\nWrite Test: Writing an array of %d doubles %d random times:\n",
            arraysize,ITERATIONS);
        printf("\tPrefetch and shared nature of L2s make this hard.\n");
        printf("\tExpected 7/8 of accesses to be miss.\n");
        }

    high=0; low=0; total=0;

    for(i=0;i<num_runs;i++) {

        PAPI_reset(eventset);
        PAPI_start(eventset);

        cache_random_write_test(array,arraysize,ITERATIONS);

        retval=PAPI_stop(eventset,&count);

        if (retval!=PAPI_OK) {
            test_fail( __FILE__, __LINE__,
                "reading PAPI_L2_DCM", retval );
        }

        if (count>high) high=count;
        if ((low==0) || (count<low)) low=count;
        total+=count;
    }

    average=(total/num_runs);

    expected=(ITERATIONS*7)/8;

//  expected=arraysize/(l1_linesize);

    error=display_error(average,high,low,expected,quiet);

    if ((error > ALLOWED_ERROR) || (error<-ALLOWED_ERROR)) {
        if (!quiet) {
            printf("Instruction count off by more "
                "than %.2lf%%\n",ALLOWED_ERROR);
        }
        errors++;
    }

    if (!quiet) printf("\n");

    /******************/
    /* Testing Reads  */
    /******************/

    if (!quiet) {
        printf("\nRead Test: Summing %d random doubles from array "
            "of size %d:\n",ITERATIONS,arraysize);
        printf("\tExpected 7/8 of accesses to be miss.\n");
        }

    high=0; low=0; total=0;

    for(i=0;i<num_runs;i++) {

        PAPI_reset(eventset);
        PAPI_start(eventset);

        aSumm+=cache_random_read_test(array,arraysize,ITERATIONS);

        retval=PAPI_stop(eventset,&count);

        if (retval!=PAPI_OK) {
            test_fail( __FILE__, __LINE__,
                "reading PAPI_L2_DCM", retval );
        }

        if (count>high) high=count;
        if ((low==0) || (count<low)) low=count;
        total+=count;
    }

    average=(total/num_runs);

    expected=(ITERATIONS*7)/8;

//  expected=arraysize/(l1_linesize/sizeof(double));

    error=display_error(average,high,low,expected,quiet);

    if ((error > ALLOWED_ERROR) || (error<-ALLOWED_ERROR)) {
        if (!quiet) {
            printf("Instruction count off by more "
                "than %.2lf%%\n",ALLOWED_ERROR);
        }
        errors++;
    }

    if (!quiet) {
        printf("\n");
    }

    /* FIXME: Warn, as we fail on broadwell and more recent chips */
    if (errors) {
        test_warn( __FILE__, __LINE__, "Error too high", 1 );
    }



    test_pass(__FILE__);

    return 0;
}