Bug#838913: libc6: There's probably a bug in libpthread, affecting several user programs.

[Florian Weimer <fw@deneb.enyo.de>]

* Aurelien Jarno:

> On 2016-09-27 13:44, Florian Weimer wrote:
>> * Aurelien Jarno:
>> 
>> > Hmm, rsync doesn't use libpthread, so that clearly rules out a
>> > libpthread issue. That said, all the example you gave fail to allocate
>> > the memory correctly, either through malloc (glibc) or mmap (kernel)
>> > which returns -ENOMEM. This points to either a kernel issue, or a
>> > limitation of the memory using for example ulimit.
>> 
>> The mm subsystem in the 4.7 upstream kernel has a very visible issue
>> which causes allocation failures:
>> 
>>   <http://marc.info/?l=linux-mm&m=147422898523307>
>>
>> There are other threads as well.  (I personally see this with the
>> xfs_inode cache.)
>> 
>> Usually it manifests in premature OOM killer invocations, but maybe
>> something the reporter's system configuration changes that (perhaps it
>> runs with vm.overcommit_memory=2?).
>  
> Indeed, that is correct. The problem has been fixed in version 4.7.5,
> while the reporter seems to run version 4.7.4. Upgrading to the latest
> kernel version would be a good start.

I don't think this has been fully fixed in 4.7.5.  I'm running that
version now, and with lots of xfs_inode objects, I observe basically
zero read-ahead, which results in stuttering media playback with
ogg123.  vm.drop_caches=3 makes the stuttgering go away.

I need to see if I can still reproduce the OOMs.  This was a bit
tricky before.