Andi Kleen <a...@linux.intel.com> writes: >> > This adds an opt-in flag to the perf_event_open() syscall to retain >> > sibling events after their file descriptors are closed. In this case, the >> > actual events will be closed with the group leader. >> >> So having the 1:1 relation with filedesc imposes a resource limit on >> userspace. >> >> This patch breaks that and enables a user to basically DoS the system by >> creating unbound events. > > The idea was to account the events in the locked memory allocation too. > Not sure that made it into the patch though.
It didn't. I can't figure out what to charge on the locked memory, as all that memory is in kernel-side objects. It also needs to make sense as iirc the default MLOCK_LIMIT is quite low, you'd hit it sooner than the file descriptor limit. > It has a minor issue that it might break some existing setups that rely > on the mmap fitting exactly into the mmap allocation, but that could > be solved by allowing a little slack, since the existing setups > likely don't have that many events. I don't see how to make this work in a sane way. Besides, if we have to have a limit anyway, sticking with the existing one is just easier and 1:1 is kind of more logical. Regards, -- Alex
