file seek is slow

Neil Hodgson nyamatongwe+thunder at gmail.com
Thu Mar 11 00:01:05 CET 2010


Metalone:

> As it turns out each call is only
> 646 nanoseconds slower than 'C'.
> However, that is still 80% of the time to perform a file seek,
> which I would think is a relatively slow operation compared to just
> making a system call.

   A seek may not be doing much beyond setting a current offset value.
It is likely that fseek(f1, 0, SEEK_SET) isn't even doing a system call.

   An implementation of fseek will often return relatively quickly when
the position is within the current buffer -- from line 192 in
http://www.google.com/codesearch/p?hl=en#XAzRy8oK4zA/libc/stdio/fseek.c&q=fseek&sa=N&cd=1&ct=rc

   Neil



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