Hi, back in 2012 [1] there was a discussion about a forking load which accumulates anon_vmas. There was a trivial test case which triggers this and can potentially deplete the memory by local user.
We have a report for an older enterprise distribution where nsd is suffering from this issue most probably (I haven't debugged it throughly but accumulating anon_vma structs over time sounds like a good enough fit) and has to be restarted after some time to release the accumulated anon_vma objects. There was a patch which tried to work around the issue [2] but I do not see any follow ups nor any indication that the issue would be addressed in other way. The test program from [1] was running for around 39 mins on my laptop and here is the result: $ date +%s; grep anon_vma /proc/slabinfo 1415960225 anon_vma 11664 11900 160 25 1 : tunables 0 0 0 : slabdata 476 476 0 $ ./a # The reproducer $ date +%s; grep anon_vma /proc/slabinfo 1415962592 anon_vma 34875 34875 160 25 1 : tunables 0 0 0 : slabdata 1395 1395 0 $ killall a $ date +%s; grep anon_vma /proc/slabinfo 1415962607 anon_vma 11277 12175 160 25 1 : tunables 0 0 0 : slabdata 487 487 0 So we have accumulated 23211 objects over that time period before the offender was killed which released all of them. The proposed workaround is kind of ugly but do people have a better idea than reference counting? If not should we merge it? --- [1] https://lkml.org/lkml/2012/8/15/765 [2] https://lkml.org/lkml/2013/6/3/568 -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
