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From: CBFalconer <cbfalconer AT yahoo DOT com>
Organization: Ched Research
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Subject: Re: Alignment problem
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Date: Mon, 11 Feb 2002 04:51:07 GMT
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CBFalconer wrote:
> 
> Eli Zaretskii wrote:
> >
> > On Sat, 9 Feb 2002, CBFalconer wrote:
> >
> > > > [1] c:\c\hashlib>gcc -c -gp -v malloc.c
> >                             ^^^
> > That should have been -pg, not -gp.
> >
> ... snip gcc -v output ...
> >
> > How did those "-gstabs+ -W -Wall" got into this this command?  Did you
> > edit your specs file or something?
> >
> Through an alias I use.
> 
... snip ...
> >
> > > Should I be using gstabs+, gstabs, or g?
> >
> > It doesn't matter, any -gSOMETHING switch will do for profiling.
> >
> > > I assume that if malloc is linked before the library search the
> > > library version will be omitted?
> >
> > Yes, of course: ld.exe is a one-pass linker.
> >
> > > All doubtless 2nd nature to you, but not to me.  Hand holding
> > > needed :-)
> >
> > Don't give up, help is on its way ;-)
> 
> Thanks.  I think that covers it when I get back to trying things
> out.

Review - this is about investigating the poor performance of free
when handling a large number of items, in no particular order.

I can now compile with -pg and get a look (with gprof) at the
performance, in terms of functions, which simply confirms the
already known problem area as free (taking up 60% of run time).
dwpmi also shows up, but this is probably an effect, not a cause. 
So the next step was to try to get detailed line information, as
follows:
(pasted as quote to avoid line wraps)

> [1] c:\c\hashlib>*gcc -c -pg -a -O2 -W -Wall -gstabs+ malloc.c
> 
> [1] c:\c\hashlib>gcc -pg -a -o hshtestp hashtest.o cokusMT.o hashlib.o malloc.o
> 
> [1] c:\c\hashlib>timerun hshtestp 4 10000
> Timer 3 on: 22:39:40
> 
> Your program caused a divide overflow error.
> If the problem persists, contact your program vendor.
> 
> [1] c:\c\hashlib>gcc -pg -o hshtestp hashtest.o cokusMT.o hashlib.o malloc.o
> 
> [1] c:\c\hashlib>timerun hshtestp 4 10000
> Timer 3 on: 22:40:09
> 
> Your program caused a divide overflow error.
> If the problem persists, contact your program vendor.
> 
> [1] c:\c\hashlib>*gcc -c -pg -O2 -W -Wall -gstabs+ malloc.c
> 
> [1] c:\c\hashlib>gcc -pg -o hshtestp hashtest.o cokusMT.o hashlib.o malloc.o
> 
> [1] c:\c\hashlib>timerun hshtestp 4 10000
> Timer 3 on: 22:42:14
> HASHLIB test04
> 
> New table, inserting 10000 values
> Status: Entries=10000, Deleted=0, Probes=48310, Misses=24413
> 
> Walking returned 0
>        0 items were inserted 0 times
>    10000 items were inserted 1 times
>        0 items were inserted 2 times
>        0 items were inserted 3 times
>        0 items were inserted 4 times
>        0 items were inserted 5 times
>        0 items were inserted 6 times
>        0 items were inserted 7 times
>        0 items were inserted 8 times
>        0 items were inserted 9 or more times
> 
> Timer 3 off: 22:42:17  Elapsed: 0:00:02.80

Once the -a option is used on malloc, the runtime blows up!  Not
sure if the -a option was needed at link time, so I tried it both
ways.

NOTE: "*gcc" runs it raw, without the default "-W -Wall -ansi -
pedantic -O2 -gstabs+" options.  timerun is an alias that starts
and stops a timer around the execution, it does not nest any
shells etc.

NOTE: The malloc source is straight out of the library source,
untouched.

Now what?

-- 
Chuck F (cbfalconer AT yahoo DOT com) (cbfalconer AT XXXXworldnet DOT att DOT net)
   Available for consulting/temporary embedded and systems.
   (Remove "XXXX" from reply address. yahoo works unmodified)
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