貌似发现了centos和rhel性能差别之谜，其中一个关键的信息可以从识别的内存中看出，具体信息如下，虽然版本不一样，凑合着用。
应该来说，rhel在编译的过程中，肯定更改了某些参数，做了某些性能调优，所以相比较而言，rhel的性能会比centos的更好。
rhel 6.3 x64 内存信息：
[root@localhost ~]# cat /proc/meminfo
MemTotal: 641656 kB
MemFree: 89576 kB
Buffers: 24124 kB
Cached: 238436 kB
SwapCached: 0 kB
Active: 131232 kB
Inactive: 292792 kB
Active(anon): 71952 kB
Inactive(anon): 92424 kB
Active(file): 59280 kB
Inactive(file): 200368 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 1835000 kB
SwapFree: 1835000 kB
Dirty: 0 kB
Writeback: 0 kB
AnonPages: 161392 kB
Mapped: 61456 kB
Shmem: 2948 kB
Slab: 74436 kB
SReclaimable: 19328 kB
SUnreclaim: 55108 kB
KernelStack: 2208 kB
PageTables: 28016 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 2155828 kB
Committed_AS: 553804 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 24116 kB
VmallocChunk: 34359694324 kB
HardwareCorrupted: 0 kB
AnonHugePages: 45056 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 8128 kB
DirectMap2M: 923648 kB
centos 6.5 x64 内存信息
[root@localhost ~]# cat /proc/meminfo
MemTotal: 882968 kB
MemFree: 221896 kB
Buffers: 72548 kB
Cached: 172604 kB
SwapCached: 4248 kB
Active: 207404 kB
Inactive: 286880 kB
Active(anon): 97400 kB
Inactive(anon): 157904 kB
Active(file): 110004 kB
Inactive(file): 128976 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 1675256 kB
SwapFree: 1649688 kB
Dirty: 52 kB
Writeback: 0 kB
AnonPages: 245544 kB
Mapped: 32704 kB
Shmem: 6172 kB
Slab: 117964 kB
SReclaimable: 56276 kB
SUnreclaim: 61688 kB
KernelStack: 2272 kB
PageTables: 28444 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 2116740 kB
Committed_AS: 943316 kB
VmallocTotal: 34359738367 kB
VmallocUsed: 24084 kB
VmallocChunk: 34359697400 kB
HardwareCorrupted: 0 kB
AnonHugePages: 83968 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 8128 kB
DirectMap2M: 903168 kB