パイプを使用するとシェルコマンドが遅くなり、中間ファイルでは速くなる

Question

中間ファイルを使用するとき、またはパイプを使用するときの処理時間のこの大きな違いを誰かが理解していますか？新しいdebian squeezeサーバーで標準ツールを使用してtiffをpdfに変換しています。これを行う標準的な方法は、最初にpsに変換することです。

パイプなし：

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

パイプ付き：

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

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

最後のコマンドの間、gsプロセスは常に100％です。

更新：
これは、ps世代のstrace出力です。

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, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0P\200\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=405128, ...}) = 0
mmap(NULL, 2501416, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fb5a14b9000
mprotect(0x7fb5a151a000, 2093056, PROT_NONE) = 0
mmap(0x7fb5a1719000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 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", O_RDONLY) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\3408\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=145048, ...}) = 0
mmap(NULL, 2240080, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fb5a1296000
mprotect(0x7fb5a12b9000, 2093056, PROT_NONE) = 0
mmap(0x7fb5a14b8000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 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, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\260\"\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=93936, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb5a1930000
mmap(NULL, 2188976, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fb5a107f000
mprotect(0x7fb5a1096000, 2093056, PROT_NONE) = 0
mmap(0x7fb5a1295000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 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, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\360>\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=530736, ...}) = 0
mmap(NULL, 2625768, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fb5a0dfd000
mprotect(0x7fb5a0e7d000, 2097152, PROT_NONE) = 0
mmap(0x7fb5a107d000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x80000) = 0x7fb5a107d000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/libc.so.6", O_RDONLY)        = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\240\355\1\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1437064, ...}) = 0
mmap(NULL, 3545160, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fb5a0a9b000
mprotect(0x7fb5a0bf4000, 2093056, PROT_NONE) = 0
mmap(0x7fb5a0df3000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x158000) = 0x7fb5a0df3000
mmap(0x7fb5a0df8000, 18504, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fb5a0df8000
close(3)                                = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb5a192f000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb5a192e000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb5a192d000
Arch_prctl(Arch_SET_FS, 0x7fb5a192e700) = 0
mprotect(0x7fb5a0df3000, 16384, PROT_READ) = 0
mprotect(0x7fb5a107d000, 4096, PROT_READ) = 0
mprotect(0x7fb5a1939000, 4096, PROT_READ) = 0
munmap(0x7fb5a1931000, 21735)           = 0
open("test.tif", O_RDONLY)              = 3
brk(0)                                  = 0x1395000
brk(0x13b6000)                          = 0x13b6000
read(3, "II*\0\10\0\0\0", 8)            = 8
fstat(3, {st_mode=S_IFREG|0644, st_size=1825656, ...}) = 0
mmap(NULL, 1825656, PROT_READ, MAP_SHARED, 3, 0) = 0x7fb5a176f000
open("/proc/meminfo", O_RDONLY)         = 4
fstat(4, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb5a1936000
read(4, "MemTotal:        2090844 kB\nMemF"..., 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, st_size=0, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb5a1936000
open("/etc/localtime", O_RDONLY)        = 4
fstat(4, {st_mode=S_IFREG|0644, st_size=1892, ...}) = 0
fstat(4, {st_mode=S_IFREG|0644, st_size=1892, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fb5a1935000
read(4, "TZif2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\4\0\0\0\4\0\0\0\0"..., 4096) = 1892
lseek(4, -1217, SEEK_CUR)               = 675
read(4, "TZif2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\6\0\0\0\6\0\0\0\0"..., 4096) = 1217
close(4)                                = 0
munmap(0x7fb5a1935000, 4096)            = 0
write(1, "%!PS-Adobe-3.0 EPSF-3.0\n%%Creato"..., 4096) = 4096
write(1, "fffffffffffffffffffffffffffff\nff"..., 4096) = 4096
write(1, "ffffffffffffffffffff\nfffffffffff"..., 4096) = 4096
write(1, "fffffffffff\nffffffffffffffffffff"..., 4096) = 4096
write(1, "ff\nfffffffffffffffffffffffffffff"..., 4096) = 4096
write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096
write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096
write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096
write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096
write(1, "ffffffffffffffffffffffff\nfffffff"..., 4096) = 4096

次に、パイプバージョンのstrace出力を示します。出力をps2pdf13にパイプすると、PSの生成が非常に遅くなるようです。

root@web5:~# strace tiff2ps test.tif | ps2pdf13 -sPAPERSIZE=a4 - > test.pdf
execve("/usr/bin/tiff2ps", ["tiff2ps", "test.tif"], [/* 28 vars */]) = 0
brk(0)                                  = 0x1b97000
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) = 0x7f9208bb1000
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) = 0x7f9208bab000
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, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0P\200\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=405128, ...}) = 0
mmap(NULL, 2501416, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f9208733000
mprotect(0x7f9208794000, 2093056, PROT_NONE) = 0
mmap(0x7f9208993000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x60000) = 0x7f9208993000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/usr/lib/libjpeg.so.62", O_RDONLY) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\3408\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=145048, ...}) = 0
mmap(NULL, 2240080, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f9208510000
mprotect(0x7f9208533000, 2093056, PROT_NONE) = 0
mmap(0x7f9208732000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x22000) = 0x7f9208732000
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, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\260\"\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=93936, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9208baa000
mmap(NULL, 2188976, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f92082f9000
mprotect(0x7f9208310000, 2093056, PROT_NONE) = 0
mmap(0x7f920850f000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x16000) = 0x7f920850f000
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, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\360>\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0644, st_size=530736, ...}) = 0
mmap(NULL, 2625768, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f9208077000
mprotect(0x7f92080f7000, 2097152, PROT_NONE) = 0
mmap(0x7f92082f7000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x80000) = 0x7f92082f7000
close(3)                                = 0
access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
open("/lib/libc.so.6", O_RDONLY)        = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\240\355\1\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1437064, ...}) = 0
mmap(NULL, 3545160, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f9207d15000
mprotect(0x7f9207e6e000, 2093056, PROT_NONE) = 0
mmap(0x7f920806d000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x158000) = 0x7f920806d000
mmap(0x7f9208072000, 18504, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f9208072000
close(3)                                = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9208ba9000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9208ba8000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9208ba7000
Arch_prctl(Arch_SET_FS, 0x7f9208ba8700) = 0
mprotect(0x7f920806d000, 16384, PROT_READ) = 0
mprotect(0x7f92082f7000, 4096, PROT_READ) = 0
mprotect(0x7f9208bb3000, 4096, PROT_READ) = 0
munmap(0x7f9208bab000, 21735)           = 0
open("test.tif", O_RDONLY)              = 3
brk(0)                                  = 0x1b97000
brk(0x1bb8000)                          = 0x1bb8000
read(3, "II*\0\10\0\0\0", 8)            = 8
fstat(3, {st_mode=S_IFREG|0644, st_size=1825656, ...}) = 0
mmap(NULL, 1825656, PROT_READ, MAP_SHARED, 3, 0) = 0x7f92089e9000
open("/proc/meminfo", O_RDONLY)         = 4
fstat(4, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9208bb0000
read(4, "MemTotal:        2090844 kB\nMemF"..., 1024) = 1024
close(4)                                = 0
munmap(0x7f9208bb0000, 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({1334836513, 114140}, NULL) = 0
fstat(1, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9208bb0000
open("/etc/localtime", O_RDONLY)        = 4
fstat(4, {st_mode=S_IFREG|0644, st_size=1892, ...}) = 0
fstat(4, {st_mode=S_IFREG|0644, st_size=1892, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9208baf000
read(4, "TZif2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\4\0\0\0\4\0\0\0\0"..., 4096) = 1892
lseek(4, -1217, SEEK_CUR)               = 675
read(4, "TZif2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\6\0\0\0\6\0\0\0\0"..., 4096) = 1217
close(4)                                = 0
munmap(0x7f9208baf000, 4096)            = 0
write(1, "%!PS-Adobe-3.0 EPSF-3.0\n%%Creato"..., 4096) = 4096
write(1, "fffffffffffffffffffffffffffff\nff"..., 4096) = 4096
write(1, "ffffffffffffffffffff\nfffffffffff"..., 4096) = 4096
write(1, "fffffffffff\nffffffffffffffffffff"..., 4096) = 4096
write(1, "ff\nfffffffffffffffffffffffffffff"..., 4096) = 4096
write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096
write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096
write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096
write(1, "ffffffffffffffffffffffffffffffff"..., 4096) = 4096
...etc...

Answer 1

編集：私は私の環境でソースファイルを使用してこれを実行し、次の結果を得ました：

[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

pvコマンドを追加して、何が起こっているのかを確認しました。これが起こったことです：

[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

ps2pdf13コマンドにパイプ処理されている50メガバイトのPostscript出力！ @jannebは、これがバッファリング/パイプの問題であるという点で正しかった。 unbufferコマンドを利用 を試してみましたが、Ghostscriptは疑似端末が好きではありません。

tiff2pdfコマンドを使用できない理由はありますか？

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

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