Linux 与交换空间相关的链接器性能

有时，用一个使用大量静态内存的小C程序来模拟一些东西是很方便的.我注意到在换上Fedora 15后，这个程序花了long分钟才完成

#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#define M 1000000
#define GIANT_SIZE (200*M)

size_t g_arr[GIANT_SIZE];

int main( int argc, char **argv){   
    int i;
    for(i = 0; i<10; i++){
        printf("This should be zero: %d\n",g_arr[i]);
    }
    exit(1);
}

这个程序有一个巨大的数组，声明大小约为

[me@bleh]$ time gcc HugeTest.c 

real    0m12.954s
user    0m6.995s
sys 0m3.890s

[me@bleh]$

13行C程序的13秒！？那是不对的.关键号码是

[me@bleh]$ time gcc HugeTest.c 

real    0m0.087s
user    0m0.026s
sys 0m0.027s

啊，更像是这样！进一步说服自己(和你自己，如果有的话)

[me@bleh]$ ls -ali /extraswap 
5986 -rw-r--r-- 1 root root 14680064000 Jul 26 15:01 /extraswap
[me@bleh]$ sudo swapon /extraswap 
[me@bleh]$ time gcc HugeTest.c 

real    4m28.089s
user    0m0.016s
sys 0m0.010s

它甚至在4.5分钟后都没有完成！

显然链接器在这里做错了什么，但我不知道怎么做

顺便说一句，这些程序都能正确编译和运行，与所有掉期业务无关.

以下是一些可能的相关信息供参考:

[]$ ulimit -a

core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 27027
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 1024
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

[]$ uname -r

2.6.40.6-0.fc15.x86_64

[]$ ld --version

GNU ld version 2.21.51.0.6-6.fc15 20110118
Copyright 2011 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License version 3 or (at your option) a later version.
This program has absolutely no warranty.

[]$ gcc --version

gcc (GCC) 4.6.1 20110908 (Red Hat 4.6.1-9)
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[]$ cat /proc/meminfo 
MemTotal:        3478272 kB
MemFree:         1749388 kB
Buffers:           16680 kB
Cached:           212028 kB
SwapCached:       368056 kB
Active:           489688 kB
Inactive:         942820 kB
Active(anon):     401340 kB
Inactive(anon):   803436 kB
Active(file):      88348 kB
Inactive(file):   139384 kB
Unevictable:          32 kB
Mlocked:              32 kB
SwapTotal:      19906552 kB
SwapFree:       17505120 kB
Dirty:               172 kB
Writeback:             0 kB
AnonPages:        914972 kB
Mapped:            60916 kB
Shmem:              1008 kB
Slab:              55248 kB
SReclaimable:      26720 kB
SUnreclaim:        28528 kB
KernelStack:        3608 kB
PageTables:        63344 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:    21645688 kB
Committed_AS:   11208980 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      139336 kB
VmallocChunk:   34359520516 kB
HardwareCorrupted:     0 kB
AnonHugePages:    151552 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:      730752 kB
DirectMap2M:     2807808 kB

TL；DR:当c程序的(大)静态内存略小于可用的交换空间时，链接器将永远无法链接程序.然而，当静态空间比可用交换空间略大larger时，它就相当快了.怎么回事！？