Messages in this thread | | | Date | Fri, 14 Nov 2014 10:06:52 -0500 | From | Rik van Riel <> | Subject | Re: anon_vma accumulating for certain load still not addressed |
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On 11/14/2014 08:08 AM, Michal Hocko wrote: > 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?
I believe we should just merge that patch.
I have not seen any better ideas come by.
The comment should probably be fixed to reflect the chain length of 5 though :)
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