show-pagemap , (c) s.kazak

// By Sergey Kazak

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <getopt.h>
#include <sysexits.h>

static uint64_t     const PAGE_SIZE = 4096;

static uint64_t read_pagecount( uint64_t pfn );
static uint64_t read_pagecgroup( uint64_t pfn );

static int o_show_details = 0, o_show_cgroup = 0, o_print_refs = 0, o_print_map_name = 0;

struct summary_t {
    uint64_t total_pages;
    uint64_t total_active_pages;
    uint64_t total_shared_pages;

} g_summary;


/*  since we cannot use here C++ std::unordered_map
    we shall use just huge arrays for calculation
*/


typedef struct var_array_t {
    uint64_t *ptr;
    uint64_t size;
} var_array_t;

static var_array_t a_per_cgroup_stats;

void init_array( var_array_t *a )
{
    a->ptr = NULL;
    a->size = 0;
}

void free_array( var_array_t *a )
{
    if( a->ptr )
        free(a->ptr);

    a->size = 0;
}

void put_or_append( var_array_t *a, uint64_t idx, uint64_t value )
{
    if( a->size < idx )
    {
        // realloc
        uint64_t new_size = idx * 1.5;
        a->ptr = realloc(a->ptr, new_size * sizeof(uint64_t));
        if( NULL == a->ptr )
            perror("failed to allocate buffer");
        // fill tail with zeroes
        memset(a->ptr + a->size, 0, (new_size - a->size) * sizeof(uint64_t));
        a->size = new_size;
    }
    a->ptr[idx] += value;
}


static void usage()
{
    fprintf( stderr, "Usage: show-pagemap [options] <PID>\n" );
    fprintf( stderr, "options are following:\n" );
    fprintf( stderr, "\t-d|--details:                  show per page details.\n" );
    fprintf( stderr, "\t-g|--cgroup:                   show cgroup refs from /proc/kpagecgroup.\n" );
    fprintf( stderr, "\t-r|--refs:                     show sharing refs from /proc/kpagecount.\n" );
    fprintf( stderr, "\t-n|--names:                    show map name if found.\n" );
}

static void dump_page(uint64_t address, uint64_t data, const char *map_name)
{
    uint64_t pfn = data & 0x7fffffffffffff;
    uint64_t cnt = o_print_refs ? (pfn ? read_pagecount(pfn) : 0) : 0;

    uint64_t page_is_present = (data >> 63) & 1;

    int64_t cgroup_id = o_show_cgroup ? read_pagecgroup(pfn) : -1;

    if( o_show_details )
    {
        printf("0x%-16lx : PFN %-16lx refs: %ld soft-dirty %ld ex-map: %ld shared %ld "
            "swapped %ld present %ld", address, pfn, cnt,
            (data >> 55) & 1,
            (data >> 56) & 1,
            (data >> 61) & 1,
            (data >> 62) & 1,
            page_is_present);

        if( cgroup_id != -1 )
            printf(" cgroup: %ld", cgroup_id);

        if( map_name )
            printf(" name: %s", map_name);

        printf("\n");
    }

    g_summary.total_pages += 1;
    g_summary.total_active_pages += page_is_present ? 1 : 0;
    g_summary.total_shared_pages += cnt > 1 ? 1 : 0;

    if( o_show_cgroup && cgroup_id > 0 && page_is_present )
    {
        put_or_append(&a_per_cgroup_stats, cgroup_id, 1);
    }
}

void print_summary()
{
    printf("Summary:\n");
    printf("total pages:       %16ld = %ld Kb\n", g_summary.total_pages, g_summary.total_pages * 4);
    printf("total active(RSS): %16ld = %ld Kb\n", g_summary.total_active_pages, g_summary.total_active_pages * 4);
    printf("total shared:      %16ld = %ld Kb\n", g_summary.total_shared_pages, g_summary.total_shared_pages * 4);

    if( o_show_cgroup && a_per_cgroup_stats.size )
    {
        printf("cgroup active pages:\n");
        for( uint64_t i = 0; i < a_per_cgroup_stats.size; ++i )
        {
            if( a_per_cgroup_stats.ptr[i] )
                printf("cgroup-id:       %8ld %8ld = %ld Kb\n", i, a_per_cgroup_stats.ptr[i], a_per_cgroup_stats.ptr[i] * 4);
        }
    }
}

void read_vma(int fd, uint64_t start, uint64_t end, const char *map_name)
{
    for(uint64_t i, val; start < end; start += PAGE_SIZE)
    {
        i = (start / PAGE_SIZE) * sizeof(uint64_t);
        if(pread(fd, &val, sizeof(uint64_t), i) != sizeof(uint64_t))
        {
            if(errno) perror("vma pread");
            break;
        }
        dump_page(i, val, map_name);
    }
}

void parse_maps( const char *maps_file, const char *pagemap_file )
{
    int maps = open(maps_file, O_RDONLY);
    if(maps < 0)
        perror("open /proc/maps failed");

    int pagemap = open(pagemap_file, O_RDONLY);
    if(pagemap < 0) {
        close(maps);
        perror("open /proc/pagemap failed");
        return;
    }

    char buffer[BUFSIZ];
    int offset = 0;
    size_t y;

    for(;;) {
        ssize_t length = read(maps, buffer + offset, sizeof buffer - offset);
        if(length <= 0) break;

        length += offset;

        for(size_t i = offset; i < (size_t)length; i ++)
        {
            uint64_t low = 0, high = 0;
            if(buffer[i] == '\n' && i)
            {
                size_t x = i - 1;
                while(x && buffer[x] != '\n') x --;
                if(buffer[x] == '\n') x ++;
                size_t beginning = x;

                while(buffer[x] != '-' && x+1 < sizeof buffer) {
                    char c = buffer[x ++];
                    low *= 16;
                    if(c >= '0' && c <= '9') {
                        low += c - '0';
                    }
                    else if(c >= 'a' && c <= 'f') {
                        low += c - 'a' + 10;
                    }
                    else break;
                }

                while(buffer[x] != '-' && x+1 < sizeof buffer) x ++;
                if(buffer[x] == '-') x ++;

                while(buffer[x] != ' ' && x+1 < sizeof buffer)
                {
                    char c = buffer[x ++];
                    high *= 16;
                    if(c >= '0' && c <= '9') {
                        high += c - '0';
                    }
                    else if(c >= 'a' && c <= 'f') {
                        high += c - 'a' + 10;
                    }
                    else break;
                }

                const char *lib_name = 0;
                if( o_print_map_name )
                {
                    for(int field = 0; field < 4; field ++) {
                        x ++;  // skip space
                        while(buffer[x] != ' ' && x+1 < sizeof buffer) x ++;
                    }
                    while(buffer[x] == ' ' && x+1 < sizeof buffer) x ++;

                    y = x;
                    while(buffer[y] != '\n' && y+1 < sizeof buffer) y ++;
                    buffer[y] = 0;

                    lib_name = buffer + x;
                }

                read_vma(pagemap, low, high, lib_name);

                if( o_print_map_name )
                    buffer[y] = '\n';
            }
        }
    }

    close(maps);
    close(pagemap);

    print_summary();
}

int main( int argc, char *argv[] )
{
    while( 1 )
    {

        static struct option long_options[] = {
            { "details",              no_argument,    NULL, 'd' },
            { "cgroup",               no_argument,    NULL, 'g' },
            { "refs",                 no_argument,    NULL, 'r' },
            { "names",                no_argument,    NULL, 'n' },
            { NULL,                             0,    NULL, 0   }
        };

        int op_c = getopt_long( argc, argv, "dgrn", long_options, NULL );
        if( op_c == -1 )
            break;

        switch( op_c )
        {
            case 'd':
                o_show_details = 1;
                break;
            case 'g':
                o_show_cgroup = 1;
                break;
            case 'r':
                o_print_refs = 1;
                break;
            case 'n':
                o_print_map_name = 1;
                break;
            default:
                fprintf( stderr, "invalid argument\n");
                exit( EXIT_FAILURE );
        }
    }

    argc -= optind;
    argv += optind;

    if( argc < 1 )
    {
        usage();
        exit( EX_USAGE );
    }

    errno = 0;
    int pid = (int)strtol(*argv, NULL, 0);
    if( errno )
    {
        perror("failed to parse PID");
        return 1;
    }

    init_array(&a_per_cgroup_stats);

    char maps_file[BUFSIZ];
    char pagemap_file[BUFSIZ];
    snprintf(maps_file, sizeof(maps_file), "/proc/%lu/maps", (uint64_t)pid);
    snprintf(pagemap_file, sizeof(pagemap_file), "/proc/%lu/pagemap", (uint64_t)pid);

    parse_maps(maps_file, pagemap_file);

    free_array(&a_per_cgroup_stats);

    return 0;
}

static int fd_pagecount = -1;

uint64_t read_pagecount( uint64_t pfn )
{
   /* This file contains a 64-bit count of the number of
   times each page is mapped, indexed by PFN.
   */
   if( -1 == fd_pagecount )
   {
      fd_pagecount = open("/proc/kpagecount", O_RDONLY);
      if( fd_pagecount < 0 )
      {
         perror("open kpagecount");
         return 0;
      }
   }

   uint64_t data, index = pfn * sizeof(uint64_t);

   if(pread(fd_pagecount, &data, sizeof(data), index) != sizeof(data)) {
      perror("pread kpagecount");
      return 0;
   }

   return data;
}

static int fd_pagecgroup = -1;

uint64_t read_pagecgroup( uint64_t pfn )
{
    /* This file contains a 64-bit inode number of the memory
              cgroup each page is charged to, indexed by page frame
              number (see the discussion of /proc/pid/pagemap).
   */

   if( -1 == fd_pagecgroup )
   {
      fd_pagecgroup = open("/proc/kpagecgroup", O_RDONLY);
      if( fd_pagecgroup < 0 )
      {
         perror("open kpagecgroup");
         return 0;
      }
   }

   uint64_t data, index = pfn * sizeof(uint64_t);

   if(pread(fd_pagecgroup, &data, sizeof(data), index) != sizeof(data)) {
      perror("pread kpagecgroup");
      return 0;
   }

   return data;
}