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Re: Committed: fix regressions by requiring fd_truncate for streamio_9.f90 and widechar_IO_1.f90

From: Janne Blomqvist <blomqvist dot janne at gmail dot com>
To: Hans-Peter Nilsson <hans-peter dot nilsson at axis dot com>
Cc: gcc-patches at gcc dot gnu dot org, fortran at gcc dot gnu dot org
Date: Mon, 06 Apr 2009 16:35:34 +0300
Subject: Re: Committed: fix regressions by requiring fd_truncate for streamio_9.f90 and widechar_IO_1.f90
References: <200904060342.n363g5H5006908@ignucius.se.axis.com>

Hans-Peter Nilsson wrote:

All fixed as per below, committed as obvious.

Thanks.

Now, there's always the chance that the added libcalls is a
regression in performance, but I trust the gfortran people being
sufficiently aware of that so I can rule it out as a less
obvious reason.

The reason is the new low level I/O library

http://gcc.gnu.org/ml/fortran/2009-01/msg00075.html

It hasn't been tuned much yet, but it seems that in general it already improves I/O performance somewhat. In some cases by massively reducing the amount of syscalls, such as of writing unformatted sequential. In other cases some extra syscalls seem to have crept in as you have observed.

--
Janne Blomqvist

References:
- Committed: fix regressions by requiring fd_truncate for streamio_9.f90 and widechar_IO_1.f90
  - From: Hans-Peter Nilsson

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