Xeon Phi troca de tmpfs do host

Question

Eu quero usar swap no Xeon Phi (mic0) usando RAM do host

No host:

# free -m
             total       used       free     shared    buffers     cached
Mem:        129022      60312      68710          0       1092      50078
-/+ buffers/cache:       9141     119880
Swap:            0          0          0

Executando este comando no host:

# mount -t ramfs ramfs /mnt/ramfs/
# dd bs=512M if=/dev/zero of=/mnt/ramfs/ram1 count=48
# echo /mnt/ramfs/ram1 >/sys/class/mic/mic0/virtblk_file
# df -a | grep ramfs
/mnt/ramfs              0          0          0    - /mnt/ramfs
# vim  /etc/mpss/default.conf # add:
ExtraCommandLine "vfs_read_optimization=on" 
ExtraCommandLine "vfs_write_optimization=on"
# service mpss stop
# micctrl --resetconfig
# service mpss start

Em seguida, execute no mic0:

# modprobe mic_virtblk 
# mkswap /dev/vda
# swapon /dev/vda
# free -m
             total       used       free     shared    buffers     cached
Mem:          7697        574       7123          0          0        145
-/+ buffers/cache:        428       7268
Swap:        24575          0      24575

Como posso garantir que a troca já esteja conectada na RAM do host?

E se ele já estiver conectado à RAM do host, por que ficou tão lento ao usar o swap no Xeon Phi?

o código de teste:

#include <stdlib.h>   
#include <stdio.h>
#include <string.h>
#include <time.h>

long timediff(clock_t t1, clock_t t2) {
    long elapsed;
    elapsed = ((double)t2 - t1) / CLOCKS_PER_SEC * 1000;
    return elapsed;
}

int main(int argc, char** argv) {
    clock_t t1, t2;
    int max = 100;
    int mb = 0;
    int size = 256;
    char* buffer;

    if(argc > 1)
        max = atoi(argv[1]);

    t1 = clock();
    while((buffer=malloc(size*1024*1024)) != NULL && mb != max) {
        memset(buffer, 0, size*1024*1024);
        ++mb;
        t2 = clock();
        printf("Allocated %.2f GB in %ld ms\n", mb * size / 1024.0, timediff(t1, t2) );
        t1 = t2;
    }      
return 0;
}

compile usando: icc swaptest.c -o swaptest -mmic

o resultado:

# ./swaptest 
Allocated 0.25 GB in 260 ms
Allocated 0.50 GB in 269 ms
...
Allocated 6.75 GB in 269 ms
Allocated 7.00 GB in 260 ms
Allocated 7.25 GB in 470 ms
Allocated 7.50 GB in 1819 ms
Allocated 7.75 GB in 2060 ms
Allocated 8.00 GB in 2420 ms
Allocated 8.25 GB in 2820 ms
Allocated 8.50 GB in 2750 ms
Allocated 8.75 GB in 2300 ms
Allocated 9.00 GB in 1380 ms
Allocated 9.25 GB in 1530 ms
Allocated 9.50 GB in 3400 ms
Allocated 9.75 GB in 3800 ms
Allocated 10.00 GB in 3940 ms
Allocated 10.25 GB in 3579 ms
Allocated 10.50 GB in 5050 ms
Allocated 10.75 GB in 5029 ms
Allocated 11.00 GB in 5130 ms
Allocated 11.25 GB in 4770 ms
Allocated 11.50 GB in 3719 ms
Allocated 11.75 GB in 2300 ms
Allocated 12.00 GB in 3619 ms

e assim por diante.

comparado ao sistema host:

$ ./a.out 
Allocated 0.25 GB in 140 ms
Allocated 0.50 GB in 170 ms
Allocated 0.75 GB in 160 ms
Allocated 1.00 GB in 160 ms
...
Allocated 23.75 GB in 130 ms
Allocated 24.00 GB in 130 ms
Allocated 24.25 GB in 130 ms
Allocated 24.50 GB in 130 ms
Allocated 24.75 GB in 130 ms
Allocated 25.00 GB in 120 ms

quando abaixo de swap: 256MB em 269 ms é de cerca de 951MB / s

ao usar swap: 256MB em 5.13 segundos é de aproximadamente 48.7MB / s, é muito mais lento que o benchmark mostrado em link (pelo menos ~ 360MB / s), este comportamento é pretendido?

Estou usando icc (ICC) 14.0.2 20140120 (parallel_studio_xe_2013_sp1_update2) e mpss-3.2.1 para Xeon Phi 5110P (rev 11)