linux – 使用管道时Shell命令慢,中间文件快

发布时间：2020-12-13 18:45:55 所属栏目：Linux 来源：网络整理

导读：有没有人理解处理时间,使用中间文件或使用管道时的巨大差异？我正在使用新的debian挤压服务器上的标准工具将tiff转换为pdf.执行此操作的标准方法是首先转换为ps. 没有管道： root@web5:~# time tiff2ps test.tif test.psreal 0m0.860suser 0m0.744ssys 0m0.1

有没有人理解处理时间,使用中间文件或使用管道时的巨大差异？我正在使用新的debian挤压服务器上的标准工具将tiff转换为pdf.执行此操作的标准方法是首先转换为ps.

没有管道：

root@web5:~# time tiff2ps test.tif > test.ps

real    0m0.860s
user    0m0.744s
sys 0m0.112s

root@web5:~# time ps2pdf13 -sPAPERSIZE=a4 test.ps > test.pdf

real    0m0.667s
user    0m0.612s
sys 0m0.060s

带管：

root@web5:~# time tiff2ps test.tif | ps2pdf13 -sPAPERSIZE=a4 - > test.pdf

real    1m6.098s
user    0m15.861s
sys 0m50.9

在最后一个命令中,gs进程始终为100％.

更新：
这是ps生成的strace输出：

root@web5:~# strace tiff2ps test.tif > test.ps
execve("/usr/bin/tiff2ps",["tiff2ps","test.tif"],[/* 28 vars */]) = 0
brk(0)                                  = 0x1395000
access("/etc/ld.so.nohwcap",F_OK)      = -1 ENOENT (No such file or directory)
mmap(NULL,8192,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANONYMOUS,-1,0) = 0x7fb5a1937000
access("/etc/ld.so.preload",R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache",O_RDONLY)      = 3
fstat(3,{st_mode=S_IFREG|0644,st_size=21735,...}) = 0
mmap(NULL,21735,PROT_READ,MAP_PRIVATE,3,0) = 0x7fb5a1931000
close(3)                                = 0
access("/etc/ld.so.nohwcap",F_OK)      = -1 ENOENT (No such file or directory)
open("/usr/lib/libtiff.so.4",O_RDONLY) = 3
read(3,"177ELF2113>1P200"...,832) = 832
fstat(3,st_size=405128,2501416,PROT_READ|PROT_EXEC,MAP_PRIVATE|MAP_DENYWRITE,0) = 0x7fb5a14b9000
mprotect(0x7fb5a151a000,2093056,PROT_NONE) = 0
mmap(0x7fb5a1719000,12288,MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE,0x60000) = 0x7fb5a1719000
close(3)                                = 0
access("/etc/ld.so.nohwcap",F_OK)      = -1 ENOENT (No such file or directory)
open("/usr/lib/libjpeg.so.62","177ELF2113>13408"...,st_size=145048,2240080,0) = 0x7fb5a1296000
mprotect(0x7fb5a12b9000,PROT_NONE) = 0
mmap(0x7fb5a14b8000,4096,0x22000) = 0x7fb5a14b8000
close(3)                                = 0
access("/etc/ld.so.nohwcap",F_OK)      = -1 ENOENT (No such file or directory)
open("/usr/lib/libz.so.1",O_RDONLY)    = 3
read(3,"177ELF2113>1260""...,st_size=93936,0) = 0x7fb5a1930000
mmap(NULL,2188976,0) = 0x7fb5a107f000
mprotect(0x7fb5a1096000,PROT_NONE) = 0
mmap(0x7fb5a1295000,0x16000) = 0x7fb5a1295000
close(3)                                = 0
access("/etc/ld.so.nohwcap",F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/libm.so.6",O_RDONLY)        = 3
read(3,"177ELF2113>1360>"...,st_size=530736,2625768,0) = 0x7fb5a0dfd000
mprotect(0x7fb5a0e7d000,2097152,PROT_NONE) = 0
mmap(0x7fb5a107d000,0x80000) = 0x7fb5a107d000
close(3)                                = 0
access("/etc/ld.so.nohwcap",F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/libc.so.6","177ELF2113>12403551"...,{st_mode=S_IFREG|0755,st_size=1437064,3545160,0) = 0x7fb5a0a9b000
mprotect(0x7fb5a0bf4000,PROT_NONE) = 0
mmap(0x7fb5a0df3000,20480,0x158000) = 0x7fb5a0df3000
mmap(0x7fb5a0df8000,18504,MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS,0) = 0x7fb5a0df8000
close(3)                                = 0
mmap(NULL,0) = 0x7fb5a192f000
mmap(NULL,0) = 0x7fb5a192e000
mmap(NULL,0) = 0x7fb5a192d000
arch_prctl(ARCH_SET_FS,0x7fb5a192e700) = 0
mprotect(0x7fb5a0df3000,16384,PROT_READ) = 0
mprotect(0x7fb5a107d000,PROT_READ) = 0
mprotect(0x7fb5a1939000,PROT_READ) = 0
munmap(0x7fb5a1931000,21735)           = 0
open("test.tif",O_RDONLY)              = 3
brk(0)                                  = 0x1395000
brk(0x13b6000)                          = 0x13b6000
read(3,"II*10",8)            = 8
fstat(3,st_size=1825656,1825656,MAP_SHARED,0) = 0x7fb5a176f000
open("/proc/meminfo",O_RDONLY)         = 4
fstat(4,{st_mode=S_IFREG|0444,st_size=0,0) = 0x7fb5a1936000
read(4,"MemTotal:        2090844 kBnMemF"...,1024) = 1024
close(4)                                = 0
munmap(0x7fb5a1936000,4096)            = 0
write(2,"TIFFReadDirectory: ",19TIFFReadDirectory: )     = 19
write(2,"Warning,",9Warning,)                = 9
write(2,"test.tif: wrong data type 7 for "...,59test.tif: wrong data type 7 for "RichTIFFIPTC"; tag ignored) = 59
write(2,".n",2.
)                      = 2
gettimeofday({1334836895,374666},NULL) = 0
fstat(1,{st_mode=S_IFREG|0664,0) = 0x7fb5a1936000
open("/etc/localtime",O_RDONLY)        = 4
fstat(4,st_size=1892,...}) = 0
fstat(4,0) = 0x7fb5a1935000
read(4,"TZif244"...,4096) = 1892
lseek(4,-1217,SEEK_CUR)               = 675
read(4,"TZif266"...,4096) = 1217
close(4)                                = 0
munmap(0x7fb5a1935000,4096)            = 0
write(1,"%!PS-Adobe-3.0 EPSF-3.0n%%Creato"...,4096) = 4096
write(1,"fffffffffffffffffffffffffffffnff"...,"ffffffffffffffffffffnfffffffffff"...,"fffffffffffnffffffffffffffffffff"...,"ffnfffffffffffffffffffffffffffff"...,"ffffffffffffffffffffffffffffffff"...,"ffffffffffffffffffffffffnfffffff"...,4096) = 4096

这是管道版本的strace输出：当输出通过管道传输到ps2pdf13时,PS生成似乎要慢得多.

root@web5:~# strace tiff2ps test.tif | ps2pdf13 -sPAPERSIZE=a4 - > test.pdf
execve("/usr/bin/tiff2ps",[/* 28 vars */]) = 0
brk(0)                                  = 0x1b97000
access("/etc/ld.so.nohwcap",0) = 0x7f9208bb1000
access("/etc/ld.so.preload",0) = 0x7f9208bab000
close(3)                                = 0
access("/etc/ld.so.nohwcap",0) = 0x7f9208733000
mprotect(0x7f9208794000,PROT_NONE) = 0
mmap(0x7f9208993000,0x60000) = 0x7f9208993000
close(3)                                = 0
access("/etc/ld.so.nohwcap",0) = 0x7f9208510000
mprotect(0x7f9208533000,PROT_NONE) = 0
mmap(0x7f9208732000,0x22000) = 0x7f9208732000
close(3)                                = 0
access("/etc/ld.so.nohwcap",0) = 0x7f9208baa000
mmap(NULL,0) = 0x7f92082f9000
mprotect(0x7f9208310000,PROT_NONE) = 0
mmap(0x7f920850f000,0x16000) = 0x7f920850f000
close(3)                                = 0
access("/etc/ld.so.nohwcap",0) = 0x7f9208077000
mprotect(0x7f92080f7000,PROT_NONE) = 0
mmap(0x7f92082f7000,0x80000) = 0x7f92082f7000
close(3)                                = 0
access("/etc/ld.so.nohwcap",0) = 0x7f9207d15000
mprotect(0x7f9207e6e000,PROT_NONE) = 0
mmap(0x7f920806d000,0x158000) = 0x7f920806d000
mmap(0x7f9208072000,0) = 0x7f9208072000
close(3)                                = 0
mmap(NULL,0) = 0x7f9208ba9000
mmap(NULL,0) = 0x7f9208ba8000
mmap(NULL,0) = 0x7f9208ba7000
arch_prctl(ARCH_SET_FS,0x7f9208ba8700) = 0
mprotect(0x7f920806d000,PROT_READ) = 0
mprotect(0x7f92082f7000,PROT_READ) = 0
mprotect(0x7f9208bb3000,PROT_READ) = 0
munmap(0x7f9208bab000,O_RDONLY)              = 3
brk(0)                                  = 0x1b97000
brk(0x1bb8000)                          = 0x1bb8000
read(3,0) = 0x7f92089e9000
open("/proc/meminfo",0) = 0x7f9208bb0000
read(4,1024) = 1024
close(4)                                = 0
munmap(0x7f9208bb0000,2.
)                      = 2
gettimeofday({1334836513,114140},{st_mode=S_IFIFO|0600,0) = 0x7f9208bb0000
open("/etc/localtime",0) = 0x7f9208baf000
read(4,4096) = 1217
close(4)                                = 0
munmap(0x7f9208baf000,4096) = 4096
...etc...

解决方法

编辑：
我在我的环境中使用您的源文件运行它,并得到以下结果：

[root@xt ~]# time tiff2ps test.tif > test.ps
real    0m0.795s
user    0m0.659s
sys     0m0.135s

[root@xt ~]# time ps2pdf13 -sPAPERSIZE=a4 test.ps > test.pdf
real    0m0.592s
user    0m0.513s
sys     0m0.075s

[root@xt ~]# time tiff2ps test.tif | ps2pdf13 -sPAPERSIZE=a4 - > test2.pdf
real    0m13.110s
user    0m4.601s
sys     0m7.260s

我添加了pv命令来查看发生了什么.这是发生的事情：

[root@xt ~]# time tiff2ps test.tif | pv | ps2pdf13 -sPAPERSIZE=a4 - > test2.pdf
50.5MB 0:00:12 [4.05MB/s] [                      <=>                                                               ]

real    0m13.934s
user    0m4.751s
sys     0m8.261s

将50兆字节的Postscript输出传送到ps2pdf13命令！
@janneb是正确的,因为这是一个缓冲/管道问题.我试过leverage the unbuffer command,但Ghostscript不喜欢伪终端.

你有什么理由不能使用tiff2pdf命令吗？

[root@xt ~]# time tiff2pdf -o test2.pdf test.tif

real    0m0.242s
user    0m0.176s
sys     0m0.064s

（编辑：李大同）

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