On Wed, Oct 05, 2016 at 02:58:12PM -0300, Mauricio Faria de Oliveira wrote: > Hi Benjamin, > > On 10/05/2016 02:41 PM, Benjamin LaHaise wrote: > >I'd suggest increasing the default limit by changing how it is calculated. > >The current number came about 13 years ago when machines had orders of > >magnitude less RAM than they do today. > > Thanks for the suggestion. > > Does the default also have implications other than memory usage? > For example, concurrency/performance of as much aio contexts running, > or if userspace could try to exploit some point with a larger number? Anything's possible when a local user can run code. It's the same problem as determining how much memory can be mlock()ed, or how much i/o a process should be allowed to do. Nothing prevents an app from doing a huge amount of readahed() calls to make the system prefetch gigabytes of data. That said, local users tend not to DoS themselves. > Wondering about it because it can be set based on num_possible_cpus(), > but that might be really large on high-end systems. Today's high end systems are tomorrow's desktops... It probably makes sense to implement per-user limits rather than the current global limit, and maybe even convert them to an rlimit to better fit in with the available frameworks for managing these things. -ben > Regards, > > -- > Mauricio Faria de Oliveira > IBM Linux Technology Center -- "Thought is the essence of where you are now." -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
