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Subject: Re: File System Performance
From: Steve Lord <lord@sgi.com>
To: Andrew Morton <akpm@zip.com.au>
Cc: Ben Israel <ben@genesis-one.com>, linux-kernel@vger.kernel.org
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Date: 12 Nov 2001 15:45:02 -0600
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On Mon, 2001-11-12 at 15:43, Andrew Morton wrote:

> 
> It's tar.  It cheats.  It somehow detects that the
> output is /dev/null, and so it doesn't read the input files.
> I think.
> 

Yep it cheats all right:

execve("/bin/tar", ["tar", "cf", "/dev/null", "linux"], [/* 30 vars */])
= 0
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 59.70    1.114097         740      1505           getdents64
 37.22    0.694516          55     12650           lstat64
  1.62    0.030264          39       775         3 open
  0.56    0.010518          14       777           close
  0.40    0.007395          10       770           fstat64
  0.24    0.004553           6       749           fcntl64
  0.11    0.001972         986         2           poll
  0.02    0.000420         210         2         2 connect
  0.02    0.000418          32        13           read
  0.02    0.000345          20        17           old_mmap
  0.02    0.000286          36         8           munmap
  0.02    0.000281          18        16           mmap2
  0.01    0.000189          47         4           socket
  0.01    0.000161          16        10           brk
  0.01    0.000101          51         2           sendto
  0.00    0.000076          15         5           mprotect
  0.00    0.000076          38         2           recvfrom
  0.00    0.000075          25         3           uname
  0.00    0.000059          30         2           readv
  0.00    0.000057          29         2           bind
  0.00    0.000056          28         2           setsockopt
  0.00    0.000039          39         1           readlink
  0.00    0.000025          13         2           getpid
  0.00    0.000023          23         1           rt_sigaction
  0.00    0.000021          21         1           time
  0.00    0.000021          21         1           gettimeofday
  0.00    0.000014           7         2           ioctl
------ ----------- ----------- --------- --------- ----------------
100.00    1.866058                 17324         5 total

Not a lot of reads in there.... I should have known it could
not go that fast.

Steve

-- 

Steve Lord                                      voice: +1-651-683-3511
Principal Engineer, Filesystem Software         email: lord@sgi.com
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