Messages in this thread | | | Subject | Re: Improving OOM killer | From | Minchan Kim <> | Date | Thu, 04 Feb 2010 00:00:54 +0900 |
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On Wed, 2010-02-03 at 17:55 +0530, Balbir Singh wrote: > * Lubos Lunak <l.lunak@suse.cz> [2010-02-03 13:10:27]: > > > On Wednesday 03 of February 2010, Balbir Singh wrote: > > > * Lubos Lunak <l.lunak@suse.cz> [2010-02-01 23:02:37]: > > > > In other words, use VmRSS for measuring memory usage instead of VmSize, > > > > and remove child accumulating. > > > > > > I am not sure of the impact of changing to RSS, although I've > > > personally believed that RSS based accounting is where we should go, > > > but we need to consider the following > > > > > > 1. Total VM provides data about potentially swapped pages, > > > > Yes, I've already updated my proposal in another mail to switch from VmSize > > to VmRSS+InSwap. I don't know how to find out the second item in code, but at > > this point of discussion that's just details. > >
We have swap count with mm-count-swap-usage.patch by Kame in mmtom.
> I am yet to catch up with the rest of the thread. Thanks for heads up. > > > > overcommit, > > > > I don't understand how this matters. Overcommit is memory for which address > > space has been allocated but not actual memory, right? Then that's exactly > > what I'm claiming is wrong and am trying to reverse. Currently OOM killer > > takes this into account because it uses VmSize, but IMO it shouldn't - if a > > process does malloc(400M) but then it uses only a tiny fraction of that, in > > the case of memory shortage killing that process does not solve anything in > > practice. > > We have a way of tracking commmitted address space, which is more > sensible than just allocating memory and is used for tracking > overcommit. I was suggesting that, that might be a better approach.
Yes. It does make sense. At least total_vm doesn't care about MAP_NORESERVE case. But unfortunately, it's a per CPU not per Process.
> > > > > > etc. > > > 2. RSS alone is not sufficient, RSS does not account for shared pages, > > > so we ideally need something like PSS. > > > > Just to make sure I understand what you mean with "RSS does not account for > > shared pages" - you say that if a page is shared by 4 processes, then when > > calculating badness for them, only 1/4 of the page should be counted for > > each? Yes, I suppose so, that makes sense. > > Yes, that is what I am speaking of
I agree. If we want to make RSS with base of badness, it's one of things we have to solve.
-- Kind regards, Minchan Kim
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