这几天在考虑存储海量图片的问题，想到 EXT4 加入了 htree 为目录做索引，性能应该有很明显的提升。
root@vps3:~/haohai/test_images# cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 16
model : 9
model name : AMD Opteron(tm) Processor 6128
stepping : 1
cpu MHz : 2000.000
cache size : 512 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 5
wp : yes
flags : fpu de tsc msr pae cx8 cmov pat clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt 3dnowext 3dnow constant_tsc up nonstop_tsc amd_dcm pni popcnt hypervisor cmp_legacy extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch nodeid_msr
bogomips : 4000.00
clflush size : 64
cache_alignment : 64
address sizes : 48 bits physical, 48 bits virtual
power management: ts ttp tm stc 100mhzsteps hwpstate
root@vps3:~/haohai/test_images# cat /proc/meminfo
MemTotal: 248828 kB
MemFree: 149548 kB
Buffers: 19496 kB
Cached: 11380 kB
SwapCached: 10480 kB
Active: 3892 kB
Inactive: 67844 kB
Active(anon): 2008 kB
Inactive(anon): 38896 kB
Active(file): 1884 kB
Inactive(file): 28948 kB
Unevictable: 0 kB
Mlocked: 0 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 248828 kB
LowFree: 149548 kB
SwapTotal: 492540 kB
SwapFree: 462712 kB
Dirty: 0 kB
Writeback: 0 kB
AnonPages: 32856 kB
Mapped: 1852 kB
Shmem: 44 kB
Slab: 23080 kB
SReclaimable: 4120 kB
SUnreclaim: 18960 kB
KernelStack: 1160 kB
PageTables: 1040 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 616952 kB
Committed_AS: 822488 kB
VmallocTotal: 602104 kB
VmallocUsed: 636 kB
VmallocChunk: 601124 kB
HardwareCorrupted: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 2048 kB
DirectMap4k: 262144 kB
DirectMap2M: 0 kB
root@vps3:~/haohai/test_images# echo 3 > /proc/sys/vm/drop_caches
root@vps3:~/haohai/test_images# time stat 553825.png
File: `553825.png'
Size: 462 Blocks: 8 IO Block: 4096 regular file
Device: ca01h/51713d Inode: 70807 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2011-07-13 06:50:31.328630002 -0500
Modify: 2011-07-13 06:50:31.336630002 -0500
Change: 2011-07-13 06:50:31.336630002 -0500
real 0m0.377s
user 0m0.000s
sys 0m0.012s
root@vps3:~/haohai/test_images# time stat 553825.png
File: `553825.png'
Size: 462 Blocks: 8 IO Block: 4096 regular file
Device: ca01h/51713d Inode: 70807 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2011-07-13 06:50:31.328630002 -0500
Modify: 2011-07-13 06:50:31.336630002 -0500
Change: 2011-07-13 06:50:31.336630002 -0500
real 0m0.007s
user 0m0.000s
sys 0m0.004s
root@vps3:~/haohai/test_images# echo 3 > /proc/sys/vm/drop_caches
root@vps3:~/haohai/test_images# time stat 553825.png
File: `553825.png'
Size: 462 Blocks: 8 IO Block: 4096 regular file
Device: ca01h/51713d Inode: 70807 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2011-07-13 06:50:31.328630002 -0500
Modify: 2011-07-13 06:50:31.336630002 -0500
Change: 2011-07-13 06:50:31.336630002 -0500
real 0m0.171s
user 0m0.004s
sys 0m0.004s
root@vps3:~/haohai/test_images# time stat 553825.png
File: `553825.png'
Size: 462 Blocks: 8 IO Block: 4096 regular file
Device: ca01h/51713d Inode: 70807 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2011-07-13 06:50:31.328630002 -0500
Modify: 2011-07-13 06:50:31.336630002 -0500
Change: 2011-07-13 06:50:31.336630002 -0500
real 0m0.006s
user 0m0.000s
sys 0m0.004s
root@vps3:~/haohai/test_images# echo 3 > /proc/sys/vm/drop_caches
root@vps3:~/haohai/test_images# time stat 553825.png
File: `553825.png'
Size: 462 Blocks: 8 IO Block: 4096 regular file
Device: ca01h/51713d Inode: 70807 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2011-07-13 06:50:31.328630002 -0500
Modify: 2011-07-13 06:50:31.336630002 -0500
Change: 2011-07-13 06:50:31.336630002 -0500
real 0m0.232s
user 0m0.004s
sys 0m0.004s
root@vps3:~/haohai/test_images#
<To Be Continue>