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Memory and Thread Placement Optimization Developer's Guide
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Examples of API Usage

This section contains code for example tasks that use the APIs that are described in this chapter.

Example 1-7 Move Memory to a Thread

The following code sample moves the memory in the address range between addr and addr+len near the next thread to touch that range.

#include <stdio.h>
#include <sys/mman.h>
#include <sys/types.h>



/*
 * Move memory to thread
 */
void
mem_to_thread(caddr_t addr, size_t len)
{
    if (madvise(addr, len, MADV_ACCESS_LWP) < 0)
        perror("madvise");
}
Example 1-8 Move a Thread to Memory

This sample code uses the meminfo() function to determine the lgroup of the physical memory backing the virtual page at the given address. The sample code then sets a strong affinity for that lgroup in an attempt to move the current thread near that memory.

#include <stdio.h>
#include <sys/lgrp_user.h>
#include <sys/mman.h>
#include <sys/types.h>


/*
 * Move a thread to memory
 */
int
thread_to_memory(caddr_t va)
{
    uint64_t    addr;
    ulong_t     count;
    lgrp_id_t   home;
    uint64_t    lgrp;
    uint_t      request;
    uint_t      valid;

    addr = (uint64_t)va;
    count = 1;
    request = MEMINFO_VLGRP;
    if (meminfo(&addr, 1, &request, 1, &lgrp, &valid) != 0) {
        perror("meminfo");
        return (1);
    }

    if (lgrp_affinity_set(P_LWPID, P_MYID, lgrp, LGRP_AFF_STRONG) != 0) {
        perror("lgrp_affinity_set");
        return (2);
    }

    home = lgrp_home(P_LWPID, P_MYID);
    if (home == -1) {
        perror ("lgrp_home");
        return (3);
    }

    if (home != lgrp)
        return (-1);

    return (0);
}
Example 1-9 Walk the lgroup Hierarchy

The following sample code walks through and prints out the lgroup hierarchy.

#include <stdio.h>
#include <stdlib.h>
#include <sys/lgrp_user.h>
#include <sys/types.h>


/*
 * Walk and print lgroup hierarchy from given lgroup
 * through all its descendants
 */
int
lgrp_walk(lgrp_cookie_t cookie, lgrp_id_t lgrp, lgrp_content_t content)
{
    lgrp_affinity_t    aff;
    lgrp_id_t          *children;
    processorid_t      *cpuids;
    int                i;
    int                ncpus;
    int                nchildren;
    int                nparents;
    lgrp_id_t          *parents;
    lgrp_mem_size_t    size;

    /*
     * Print given lgroup, caller's affinity for lgroup,
     * and desired content specified
     */
    printf("LGROUP #%d:\n", lgrp);

    aff = lgrp_affinity_get(P_LWPID, P_MYID, lgrp);
    if (aff == -1)
        perror ("lgrp_affinity_get");
    printf("\tAFFINITY: %d\n", aff);

    printf("CONTENT %d:\n", content);

    /*
     * Get CPUs
     */
    ncpus = lgrp_cpus(cookie, lgrp, NULL, 0, content);
    printf("\t%d CPUS: ", ncpus);
    if (ncpus == -1) {
        perror("lgrp_cpus");
        return (-1);
    } else if (ncpus > 0) {
        cpuids = malloc(ncpus * sizeof (processorid_t));
        ncpus = lgrp_cpus(cookie, lgrp, cpuids, ncpus, content);
                if (ncpus == -1) {
            free(cpuids);
                           perror("lgrp_cpus");
            return (-1);
        }
        for (i = 0; i < ncpus; i++)
            printf("%d ", cpuids[i]);
        free(cpuids);
    }
    printf("\n");

    /*
     * Get memory size
     */
    printf("\tMEMORY: ");
    size = lgrp_mem_size(cookie, lgrp, LGRP_MEM_SZ_INSTALLED, content);
    if (size == -1) {
        perror("lgrp_mem_size");
        return (-1);
    }
    printf("installed bytes 0x%llx, ", size);
    size = lgrp_mem_size(cookie, lgrp, LGRP_MEM_SZ_FREE, content);
        if (size == -1) {
        perror("lgrp_mem_size");
        return (-1);
    }
    printf("free bytes 0x%llx\n", size);

    /*
     * Get parents
     */
    nparents = lgrp_parents(cookie, lgrp, NULL, 0);
    printf("\t%d PARENTS: ", nparents);
    if (nparents == -1) {
        perror("lgrp_parents");
        return (-1);
    } else if (nparents > 0) {
        parents = malloc(nparents * sizeof (lgrp_id_t));
        nparents = lgrp_parents(cookie, lgrp, parents, nparents);
                   if (nparents == -1) {
            free(parents);
                        perror("lgrp_parents");
            return (-1);
                   }
        for (i = 0; i < nparents; i++)
            printf("%d ", parents[i]);
        free(parents);
    }
    printf("\n");

    /*
     * Get children
     */
    nchildren = lgrp_children(cookie, lgrp, NULL, 0);
    printf("\t%d CHILDREN: ", nchildren);
    if (nchildren == -1) {
        perror("lgrp_children");
        return (-1);
    } else if (nchildren > 0) {
        children = malloc(nchildren * sizeof (lgrp_id_t));
        nchildren = lgrp_children(cookie, lgrp, children, nchildren);
                   if (nchildren == -1) {
            free(children);
                        perror("lgrp_children");
            return (-1);
                   }
        printf("Children: ");
        for (i = 0; i < nchildren; i++)
            printf("%d ", children[i]);
        printf("\n");

        for (i = 0; i < nchildren; i++)
            lgrp_walk(cookie, children[i], content);

        free(children);
    }
    printf("\n");

    return (0);
}
Example 1-10 Find the Closest lgroup With Available Memory Outside a Given lgroup
#include <stdio.h>
#include <stdlib.h>
#include <sys/lgrp_user.h>
#include <sys/types.h>


#define    INT_MAX    2147483647


/*
 * Find next closest lgroup outside given one with available memory
 */
lgrp_id_t
lgrp_next_nearest(lgrp_cookie_t cookie, lgrp_id_t from)
{
    lgrp_id_t          closest;
    int                i;
    int                latency;
    int                lowest;
    int                nparents;
    lgrp_id_t          *parents;
    lgrp_mem_size_t    size;


    /*
     * Get number of parents
     */
    nparents = lgrp_parents(cookie, from, NULL, 0);
    if (nparents == -1) {
        perror("lgrp_parents");
        return (LGRP_NONE);
    }

    /*
     * No parents, so current lgroup is next nearest
     */
    if (nparents == 0) {
        return (from);
    }

    /*
     * Get parents
     */
    parents = malloc(nparents * sizeof (lgrp_id_t));
    nparents = lgrp_parents(cookie, from, parents, nparents);
    if (nparents == -1) {
        perror("lgrp_parents");
        free(parents);
        return (LGRP_NONE);
        }

    /*
     * Find closest parent (ie. the one with lowest latency)
     */
    closest = LGRP_NONE;
    lowest = INT_MAX;
    for (i = 0; i < nparents; i++) {
        lgrp_id_t    lgrp;

        /*
         * See whether parent has any free memory
         */
        size = lgrp_mem_size(cookie, parents[i], LGRP_MEM_SZ_FREE,
            LGRP_CONTENT_ALL);
        if (size > 0)
            lgrp = parents[i];
        else {
            if (size == -1)
                perror("lgrp_mem_size");

            /*
             * Find nearest ancestor if parent doesn't
             * have any memory
             */
            lgrp = lgrp_next_nearest(cookie, parents[i]);
            if (lgrp == LGRP_NONE)
                continue;
        }

        /*
         * Get latency within parent lgroup
         */
        latency = lgrp_latency_cookie(lgrp, lgrp);
        if (latency == -1) {
            perror("lgrp_latency_cookie");
            continue;
        }

        /*
         * Remember lgroup with lowest latency
         */
        if (latency < lowest) {
            closest = lgrp;
            lowest = latency;
        }
    }

    free(parents);
    return (closest);
}


/*
 * Find lgroup with memory nearest home lgroup of current thread
 */
lgrp_id_t
lgrp_nearest(lgrp_cookie_t cookie)
{
    lgrp_id_t    home;
    longlong_t    size;

    /*
     * Get home lgroup
     */
    home = lgrp_home(P_LWPID, P_MYID);

    /*
     * See whether home lgroup has any memory available in its hierarchy
     */
    size = lgrp_mem_size(cookie, home, LGRP_MEM_SZ_FREE,
        LGRP_CONTENT_ALL);
    if (size == -1)
        perror("lgrp_mem_size");

    /*
     * It does, so return the home lgroup.
     */
    if (size > 0)
        return (home);

    /*
     * Otherwise, find next nearest lgroup outside of the home.
     */
    return (lgrp_next_nearest(cookie, home));
}
Example 1-11 Find Nearest lgroup With Free Memory

This example code finds the nearest lgroup with free memory to a given thread's home lgroup.

lgrp_id_t
lgrp_nearest(lgrp_cookie_t cookie)
{
        lgrp_id_t         home;
        longlong_t        size;

        /*
         * Get home lgroup
         */

        home = lgrp_home();

        /*
         * See whether home lgroup has any memory available in its hierarchy
         */

        if (lgrp_mem_size(cookie, lgrp, LGRP_MEM_SZ_FREE,
            LGRP_CONTENT_ALL, &size) == -1)
                perror("lgrp_mem_size");

        /*
         * It does, so return the home lgroup.
         */

        if (size > 0)
                return (home);

        /*
         * Otherwise, find next nearest lgroup outside of the home.
         */

        return (lgrp_next_nearest(cookie, home));
}
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