于 2011年11月04日 05:54, Glauber Costa 写道: > On 11/03/2011 06:13 PM, Brian K. White wrote: >> On 11/3/2011 3:25 PM, Glauber Costa wrote: >>> On 11/03/2011 05:20 PM, Max Kellermann wrote: >>>> On 2011/11/03 20:03, Alan Cox<alan@xxxxxxxxxxxxxxxxxxx> wrote: >>>>> Sure - I'm just not seeing that a whole separate cgroup for it is >>>>> appropriate or a good plan. Anyone doing real resource management needs >>>>> the rest of the stuff anyway. >>>> >>>> Right. When I saw Frederic's controller today, my first thought was >>>> that one could move the fork limit code over into that controller. If >>>> we reach a consensus that this would be a good idea, and would have >>>> chances to get merged, I could probably take some time to refactor my >>>> code. >>>> >>>> Max >>> I'd advise you to take a step back and think if this is really needed. >>> As Alan pointed out, the really expensive resource here is already being >>> constrained by Frederic's controller. >> >> I think this really is a different knob that is nice to have as long as >> it doesn't cost much. It's a way to set a max lifespan in a way that >> isn't really addressed by the other controls. (I could absolutely be >> missing something.) >> >> I think Max explained the issue clearly enough. > > He did, indeed. > >> It doesn't matter that the fork itself is supposedly so cheap. >> >> It's still nice to have a way to say, you may not fork/die/fork/die/fork >> in a race. >> >> What's so unimaginable about having a process that you know needs a lot >> of cpu and ram or other resources to do it's job, and you expressly want >> to allow it to take as much of those resources as it can, but you know >> it has no need to fork, so if it forks, _that_ is the only indication of >> a problem, so you may only want to block it based on that. >> >> Sure many other processes would legitimately fork/die/fork/die a lot >> while never exceeding a few total concurrent tasks, and for them you >> would not want to set any such fork limit. So what? >> > As I said previously, he knows his use cases better than anyone else. > If a use case can be found in which the summation of cpu+task controllers is not enough, and if this is implemented as an option to the task controller, and does not make it: > 1) confusing, > 2) more expensive, > > then I don't see why not we shouldn't take it. Quoted from Lennart's reply in another mail thread: "Given that shutting down some services might involve forking off a few things (think: a shell script handling shutdown which forks off a couple of shell utilities) we'd want something that is between "from now on no forking at all" and "unlimited forking". This could be done in many different ways: we'd be happy if we could do time-based rate limiting, but we'd also be fine with defining a certain budget of additional forks a cgroup can do (i.e. "from now on you can do 50 more forks, then you'll get EPERM)." (http://lkml.org/lkml/2011/10/19/468) The last sentence suggests he might like this fork controller. -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
