Messages in this thread | | | Subject | Re: RSS accounting (was: Re: 2.6.19-rc1-mm1) | From | Arjan van de Ven <> | Date | Tue, 10 Oct 2006 18:13:10 +0200 |
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On Tue, 2006-10-10 at 15:14 +0200, Peter Zijlstra wrote: > > > > We need to consider at least if any of the following are part of rss: > > * VM_IO io mmaped device stuff > > * Non-linear mappings > > * Shared hugetlb memory that shares pagetables > > * Shared hugetlb memory > > * Hugetlb memory in general > > * Shared normal memory that shares pagetables > > * Shared normal memory (file backed; eg pagecache) > > * Shared normal memory (anonymous/non-file-backed) > > * Sysv/ipc shared memory > > * Not shared normal memory
> So we have three cases where RSS matters besides presenting a number to > user-space; > - shared page tables > - containers > - rlimit > > Preferably they will all share a common definition of what RSS is; since > containers must account shared pages somehow (not doing so would open up > a large hole to DoS the other containers) and the container case can be > argued to be an extension of the rlimit case we cannot just ignore them. > > As then what to do with them, I've yet to figure out. Some random bit > floating in my brain; > - VM_IO can be discarted, its not actual memory
agreed (although I think we do count it today; this is half of what makes X look so bloated, next to firefox ;)
> > - hugetlb is memory too, so I'd not special case this (other than the > different unit of accounting)
agreed again; personally I don't think hugetlb memory should be special; especially with all the libhugetlbfs work on making it real easy for apps to use; the more it's used the more people would notice something funky with it.
> - shared mapped pages could be accounted on vma level, since both > containers have access to the same file, there is already an imbalance, > so I'd not worry about the 1%-99% usage scenario here.
or one level below; if you count it in the actual PTE page then the sharing case will "just work". It's a trick question; do you count it as 100% or do you count it as 100% / number of sharers.
> - regular, non mapped, pagecache pages however have no owner - what to > do. (fake vma - which would result in each container paying equally for > all these pages?)
if they're clean I wouldn't count them to anything actually
> Anyway, I'd rather not break RSS twice, once now because we don't quite > know what to do, and later when we do get an acceptable mm container and > have to include shared memory in one way or the other.
RSS of a container versus RSS of a process is an interesting question for sure ;)
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