[yocto] liblzma: memory allocation failed

[Peter Bergin]

On 2018-09-17 10:27, Burton, Ross wrote:
> On Mon, 17 Sep 2018 at 08:13, Peter Bergin<peter at 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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