On 2018-09-17 10:27, Burton, Ross wrote:
On Mon, 17 Sep 2018 at 08:13, Peter Bergin<pe...@berginkonsult.se> wrote:
I'm pretty sure I have narrowed down the root cause to the restriction
of virtual memory and that liblzma base its memory calculations on
physical RAM.
To prove this I added a printout in rpm-native/rpmio/rpmio.c and the
function lzopen_internal.
uint64_t memory_usage = lzma_stream_encoder_mt_memusage(&mt_options);
rpmlog(RPMLOG_NOTICE, "DBG: memory_usage %lu\n", memory_usage);
The value of memory_usage is the same regardless of which 'ulimit -v'
value I set. On the host with 256GB of physical RAM and 32GB of virtual
memory, memory_usage is ~5.1GB. On another host with 16GB of physical
RAM I get memory_usage of ~660MB.
I guess you have not seen this kind of failure if you not have
restricted virutal memory on your host. If you want to try to reproduce
this set 'ulimit -v 8388608' (8GB) in your shell and then 'bitbake
glibc-locale -c package_write_rpm -f'.
Wouldn't a solution be to change lzma to look at free memory, not
total physical memory?
Ross
I have been in contact with the maintainer of liblzma. There is
currently no way to restrict the memory usage in liblzma during multi
threaded compression. He recommended to adjust the number of threads
used during compression. This kind of check is done for 32-bits but not
when running 64-bits (in rpmio/rpmio.c lzopen_internal). To rewrite
liblzma is another option but I took an easier way out.
I have come up with a patch
(https://patchwork.openembedded.org/patch/155017/) that solves my
problem and do a restriction of memory usage when the 'ulimit -v' is
set. The calculation is based on the assumption that lzopen_internal is
run in parallel with as many instances as cpu threads as '#pragma omp
parallel' is used in build/pack.c.
When running test on my machine with 4 cores 16GB of physical RAM and
'ulimit -v 2097152' (2GB). It works good and the log shows:
XZ: virtual memory restricted to 2147483648 and per CPU thread 536870912
XZ: Adjusted the number of threads from 4 to 3 to not exceed the memory
usage limit of 2147483648 bytes
Didn't get a clear answer if this is something Yocto/OE should support
but I hope my patch solves the issue and it will not affect the normal
environments where 'ulimit -v' is not set.
/Peter
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