A recent patch increased GCC's memory consumption in some cases!

[Richard Guenther]

On Thu, 18 Jan 2007, Jan Hubicka wrote:

> > On Thu, 18 Jan 2007, Jan Hubicka wrote:
> > 
> > > > 
> > > > comparing PR rtl-optimization/28071 testcase compilation at -O2 level:
> > > >   Ovarall memory allocated via mmap and sbrk decreased from 365202k to 192018k, overall -90.19%
> > > >   Peak amount of GGC memory allocated before garbage collecting increased from 207227k to 302461k, overall 45.96%
> > > >   Peak amount of GGC memory still allocated after garbage collecting decreased from 192563k to 178766k, overall -7.72%
> > > >   Amount of produced GGC garbage increased from 355277k to 586684k, overall 65.13%
> > > >   Amount of memory still referenced at the end of compilation decreased from 30387k to 27902k, overall -8.91%
> > > 
> > > This result is somewhat bogus, the memory consumption indeed peaks after
> > > 360MB.  Richard, is it possible for your script to miss the real peak
> > > somehow? See  http://www.suse.de/~aj/SPEC/amd64/memory/pr28071-O2.rep
> > > All the 240MB of memory are produced by schedule2 pass and we GGC it
> > > immediately, so I guess the peak happens just for a short time.
> > 
> > Well, it tracks the peak VM usage - independent on for how long it
> > happens.  A more stable (less gc-change error-prone) quantity to
> > measure would be for example the sum of all allocations done.  But of
> > course changing it will break all history.
> 
> We compute sum of all allocations, your script is really meant to
> provide real peak.  Problem here is that the real peak is >400MB (i've
> just verified it by looking at TOP scores and it is output by GGC {GC
> ... -> ...) if you look at the link above) and it is all loglinks
> produced by scheduler, but 192MB is reported by the script for whatever
> reason.

Maybe we miss to strace some important allocation function -- which
system do you measure on?  Or we miss some strace events or the
filtering does not match correctly for your system.

Richard.

--
Richard Guenther <rguenther@suse.de>
Novell / SUSE Labs