http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54056
Bug #: 54056
Summary: Fast run out of memory compiling template
specialization
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: sergey.prokhore...@gmail.com
Created attachment 27848
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27848
Test case to reproduce.
The attached file, compiled with both g++ 4.6.3 and g++ 4.7.0, quickly eats up
all memory and swap space.
The similar templates source in a real project quickly (in 10-20 seconds) eat
16GB of memory, swaps out and die. But when compiled with g++ 4.5.2 it does not
run out of memory. We found this trying to move to 4.6 or 4.7.
Also, the bug does not happen if the attached test case is compiled with
-DNOSWAPBUG. In this case a template without extra parameter is used. This was
found in the real project, where I compiled 30MB preprocessed file and it did
not eat memory if the "buggy" templates form (with 2 parameters) was replaced
with the NOSWAPBUG one.
I used a generator to produce test case. On my simple machine that I use now to
test with 1GB of memory, max number of templates it can handle is 200. With 300
it quickly takes up all memory and swap space.
Here's -ftime-report for 200 structs:
Execution times (seconds)
phase setup : 0.01 ( 1%) usr 0.00 ( 0%) sys 0.02 ( 1%) wall
1438 kB ( 1%) ggc
phase parsing : 1.36 (98%) usr 0.16 (94%) sys 1.52 (81%) wall
234458 kB (99%) ggc
phase lang. deferred : 0.02 ( 1%) usr 0.00 ( 0%) sys 0.17 ( 9%) wall
0 kB ( 0%) ggc
phase cgraph : 0.00 ( 0%) usr 0.01 ( 6%) sys 0.13 ( 7%) wall
131 kB ( 0%) ggc
phase generate : 0.02 ( 1%) usr 0.01 ( 6%) sys 0.33 (18%) wall
132 kB ( 0%) ggc
|name lookup : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 1%) wall
307 kB ( 0%) ggc
garbage collection : 0.02 ( 1%) usr 0.00 ( 0%) sys 0.15 ( 8%) wall
0 kB ( 0%) ggc
callgraph construction : 0.00 ( 0%) usr 0.01 ( 6%) sys 0.04 ( 2%) wall
131 kB ( 0%) ggc
callgraph optimization : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.06 ( 3%) wall
0 kB ( 0%) ggc
varpool construction : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.03 ( 2%) wall
0 kB ( 0%) ggc
preprocessing : 0.00 ( 0%) usr 0.00 ( 0%) sys 0.01 ( 1%) wall
29 kB ( 0%) ggc
parser (global) : 0.00 ( 0%) usr 0.02 (12%) sys 0.02 ( 1%) wall
767 kB ( 0%) ggc
parser struct body : 1.31 (94%) usr 0.14 (82%) sys 1.42 (76%) wall
231197 kB (98%) ggc
template instantiation : 0.05 ( 4%) usr 0.00 ( 0%) sys 0.07 ( 4%) wall
2442 kB ( 1%) ggc
TOTAL : 1.39 0.17 1.87
236046 kB
And to compare here's exactly same 200 struct report but with -DNOSWAPBUG:
phase setup : 0.01 (20%) usr 0.00 ( 0%) sys 0.02 (33%) wall
1438 kB (55%) ggc
phase parsing : 0.04 (80%) usr 0.01 (100%) sys 0.04 (67%) wall
1024 kB (39%) ggc
|name lookup : 0.02 (40%) usr 0.00 ( 0%) sys 0.01 (17%) wall
216 kB ( 8%) ggc
preprocessing : 0.00 ( 0%) usr 0.01 (100%) sys 0.01 (17%) wall
29 kB ( 1%) ggc
parser (global) : 0.02 (40%) usr 0.00 ( 0%) sys 0.02 (33%) wall
551 kB (21%) ggc
parser struct body : 0.02 (40%) usr 0.00 ( 0%) sys 0.01 (17%) wall
282 kB (11%) ggc
TOTAL : 0.05 0.01 0.06
2607 kB
Not only memory 230KB vs 2KB, but compilation time is 1.39s vs 0.05s.
My environment at work is Ubuntu 11.10 x86_64, so 64 bit compiler, and Ubuntu
12.04 at home, also 64 bit.
