Dear Jerry, This is OK for trunk. Maybe it is best to leave it for a week or two before committing to the branches?
Thanks for the patch. Paul On 7 February 2015 at 03:08, Jerry DeLisle <jvdeli...@charter.net> wrote: > With the attached patch I create a special version of fbuf_flush that is > only called with list directed I/O. There can be no tabbing back and forth > so it is safe to flush the buffer whenever we want. The bug occurs when the > buffer keeps growing to no end until no more allocations can be made and the > OS gives an error. > > fbuf_flush can be called as much as one wants to, but to keep overhead low, > I introduce a new version with an arbitrary limit. If below the limit, just > return doing no flushing. When the limit is exceeded, fbuf is flushed. The > code to do this is duplicated from the original fbuf_flush so it is very > safe and well tested. > > I played with the allowable maximum position limit for flushing and ran some > timing tests. My machine here uses a solid state drive which may bias the > results somewhat. Others are welcome to test and see what values they get > as well. I settled on 524588 based on these results, favoring writing over > reading a little. > > The patch has zero impact on any other type of I/O including normal > formatted I/O. I also tested to confirm that formatted I/O does not have > the problem. It is flushed regularly in the main transfer loop. As far as > I can tell only list directed has the issue. > > I get the following timings using the attached test program. > > WRITING: > Array Size--> 1000000 100000000 > Buf Limit > > 16384 2.107 210.9 > 32768 2.026 292.1 > 65636 2.232 235.8 > 524288 1.958 193.5 > 1048576 2.023 203.5 > > > READING: > Buf Limit > > 16384 1.843 184.4 > 32768 1.841 186.8 > 65636 1.816 197.6 > 524288 1.879 186.5 > 1048576 1.834 185.2 > > Regression tested on x86-64 Linux. > > OK for trunk followed by backports? > > I can not include a specific testsuite test case, it would take way too long > to run. > > Regards, > > Jerry > > 2015-02-07 Jerry DeLisle <jvdeli...@gcc.gnu.org> > > PR libgfortran/60956 > * io/fbuf.c (fbuf_flush_list): New function that only flushes > if current fbuf position exceeds a limit. > * io/fbuf.h: Declare the new function. > * io/io.h (enum unit_mode): Add two new modes. > * io/list_read.c (list_formatted_read_scalar): Call new function. > * io/write.c: Include fbuf.h. (list_formatted_write_scalar): > Call new function. -- Outside of a dog, a book is a man's best friend. Inside of a dog it's too dark to read. Groucho Marx
