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Re: gcc behavior on memory exhaustion


On 09/08/17 14:05, Andrew Roberts wrote:
I routinely build the weekly snapshots and RC's, on x64, arm and aarch64.

The last gcc 8 snapshot and the two recent 7.2 RC's have failed to build on aarch64 (Raspberry Pi 3, running Arch Linux ARM). I have finally traced this to the system running out of memory. I guess a recent kernel update had changed the memory page size and the swap file was no longer being used because the page sizes didn't match.

Obviously this is my issue, but the error's I was getting from gcc did not help. I was getting ICE's, thus:

/usr/local/gcc/bin/g++ -Wall -Wextra -Wno-ignored-qualifiers -Wno-sign-compare -Wno-write-strings -std=c++14 -pipe -march=armv8-a -mcpu=cortex-a53 -mtune=cortex-a53 -ftree-vectorize -O3 -DUNAME_S=\"linux\" -DUNAME_M=\"aarch64\" -DOSMESA=1 -I../libs/include -DRASPBERRY_PI -I/usr/include/freetype2 -I/usr/include/harfbuzz -I/usr/include/unicode -c -o glerr.o glerr.cpp
{standard input}: Assembler messages:
{standard input}: Warning: end of file not at end of a line; newline inserted {standard input}:204: Error: operand 1 must be an integer register -- `mov' {standard input}: Error: open CFI at the end of file; missing .cfi_endproc directive
g++: internal compiler error: Killed (program cc1plus)
Please submit a full bug report,
with preprocessed source if appropriate.
See <https://gcc.gnu.org/bugs/> for instructions.
make: *** [<builtin>: glerr.o] Error 4
make: *** Waiting for unfinished jobs....

I was seeing the problem when building using make -j2. Both building gcc and building large user projects.

There are two issues here:

1) There was discussion about increasing the amount of memory gcc would reserve to help speed up compilation of large source files, I wondered if this could be a factor.

2) It would be nice to see some sort of out of memory error, rather than just an ICE.

The system has 858Mb of  RAM without the swap file.

Building a single source file seems to use up to 97% of the available memory (for a 2522 line C++ source file).

make -j2 is enough to cause the failure.

Regards

Andrew Roberts

For what its worth, if I disable the swap on a 32 bit Raspberry Pi3 (armv7l), with 936Kb free memory, building my project with make -j4, only uses 33% of the memory, and does not ICE.

So there seems a huge memory usage regression for aarch64 vs arm. Nearly 3x the memory usage is more than you would expect by doubling pointer sizes. Does aarch64 use a different default preallocation of memory?

Regards

Andrew


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