On Wed, 20 Apr 2011, Jeff Law wrote:
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On 04/20/11 15:08, Dimitrios Apostolou wrote:
Hello list,
while trying to build gcc-4.6.0 on my sparcstation, I got gengtype OOM
killed. That's when I noticed that its RAM usage peaks at 150MB, which
is a bit excessive for parsing a ~500K text file.
The attached patch fixes the leak and gengtype now uses a peak of 4MB
heap. Hopefully I don't do something wrong, since it took me a while to
understand those obstacks...
The code in question creates an obstack, allocates (and grows) a single
object on the obstack, then frees the object. This leaks the underlying
obstack structure itself and potentially any chunks that were too small
to hold the object.
Plus a whole page which is preallocated by the obstack, if I understand
correctly. As a result, for each word in the text file we consume 4KB,
which are never freed.
It turns out there's a similar leak in gengtype.c which is fixed in the
same way.
Nice, thanks for looking deeper into this, I just stopped when memory
utilisation seemed ok.
A quick valgrind test shows that prior to your change gengtype leaked
roughly 200M, after your change it leaks about 1.3M and after fixing
gengtype it leaks a little under 300k.
I'll run those changes through the usual tests and check in the changes
assuming they pass those tests.
Thanks for the patch!
P.S. I was trying to test gcc on a rare arch (sparc-unknown-linux-gnu)
but unfortunately the sparcstation crashed and burned after this, so I
can't continue the build and report back :-(
:( My old PA box has similar problems, though it merely overheats
before a bootstrap can complete, so in theory I could coax it to finish
a bootstrap. Luckily others (particularly John) have stepped in over
the last decade and taken excellent care of the PA port.
If by PA you mean PA-RISC, I remember when I had access to a Visualize
C200 with gentoo on. I loved the machine, but it had an important issue:
it was absolutely random if it would power up, when pressing the power
button. But as long as we never turned it off, it worked ok :-)
Dimitris
