Extremely slooooow __sys_ftruncate?

[Kip Macy]

"truncate" may be synchronous on FreeBSD - almost nothing is on Linux.

   -Kip

On Thu, Mar 20, 2008 at 8:02 PM, Steve Kargl
<sgk at troutmask.apl.washington.edu> wrote:
> In the process of helping to debug a problem with gcc-4.4.0
>  (actually a gfortran problem), I run gprof on the executable.
>  The profile shows that __sys_ftruncate is extremely slow.
>
>   %   cumulative   self              self     total
>   time   seconds   seconds    calls  ms/call  ms/call  name
>   85.6       6.05     6.05    51830     0.12     0.12  __sys_ftruncate [2]
>   5.6       6.44     0.40        0  100.00%           .mcount (101)
>   1.7       6.56     0.12    51872     0.00     0.00  _lseek [5]
>   1.6       6.67     0.11    52055     0.00     0.00  sigprocmask [6]
>   0.8       6.73     0.06   103687     0.00     0.00  memset [14]
>   0.4       6.76     0.03      488     0.06     0.06  __sys_write [18]
>   0.4       6.79     0.03        0  100.00%           formatted_transfer_scalar
>
>  time ./z
>      184.21 real         0.98 user         6.57 sys
>
>  This program should finish well under 184 seconds.  The same program
>  and exact same gcc/gfortran source on linux shows
>   real    0m0.555s    user    0m0.103s    sys     0m0.452s
>
>  Is __sys_ftruncate known to have performance problems?
>
>  --
>  Steve
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