Messages in this thread | | | Date | Wed, 28 Jan 2009 06:36:43 +0100 | From | Willy Tarreau <> | Subject | Re: [patch 016/104] epoll: introduce resource usage limits |
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On Tue, Jan 27, 2009 at 09:26:30PM -0800, Greg KH wrote: > On Tue, Jan 27, 2009 at 08:10:41PM -0800, Davide Libenzi wrote: > > In my servers, I know if they are going to be loaded, and I bump NFILES > > (and a few other things) to the correct place. Since many of those > > limits do not actually pre-allocate any resource, I don't need to wait and > > monitor the values, before taking proper action. > > But what about people who want to know what the current usages are, so > that they _can_ monitor things and adjust them on the fly if things are > about to go boom? > > I see no reason why we can't leave the value where it is today, and add > the ability to both turn the limits off entirely, and also report our > current usage. That keeps the DOS from happening on "default" systems, > and lets admins have an idea if they need to bump up the values on their > systems as well. > > I don't understand your objection to allowing the usage to be monitored.
Agreed. If sysadmins get trapped by the upgrade, the fix for an hypotethical DoS is a 100%-certain DoS by itself. The general sense that "if it's not broken, don't fix it" applies here as well. The server's sysadmin should not be bothered by a security upgrade (anyway, after a few minutes of havoc in prod, he will revert to previous version without trying to understand any further). But the campus sysadmin having trouble with local users already spends a lot of time tweaking limits. Now we offer them a new limit they can tune, they'll happily use it. Anyway, even at 128 they'll probably lower it down a lot. So basically we're with a medium value which does not fit any usage.
Willy
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