Peter Zijlstra <[email protected]> writes: > On Fri, Oct 24, 2014 at 10:44:54AM +0300, Alexander Shishkin wrote: >> Peter Zijlstra <[email protected]> writes: >> >> > On Mon, Oct 13, 2014 at 04:45:46PM +0300, Alexander Shishkin wrote: >> >> Normally, per-task events can't be inherited parents' ring buffers to >> >> avoid multiple events contending for the same buffer. And since buffer >> >> allocation is typically done by the userspace consumer, there is no >> >> practical interface to allocate new buffers for inherited counters. >> >> >> >> However, for kernel users we can allocate new buffers for inherited >> >> events as soon as they are created (and also reap them on event >> >> destruction). This pattern has a number of use cases, such as event >> >> sample annotation and process core dump annotation. >> >> >> >> When a new event is inherited from a per-task kernel event that has a >> >> ring buffer, allocate a new buffer for this event so that data from the >> >> child task is collected and can later be retrieved for sample annotation >> >> or core dump inclusion. This ring buffer is released when the event is >> >> freed, for example, when the child task exits. >> >> >> > >> > This causes a pinned memory explosion, not at all nice that. >> > >> > I think I see why and all, but it would be ever so good to not have to >> > allocate so much memory. >> >> Are there any controls we could use to limit such memory usage? > > I'd say the same limit we're already accounting the mmap()s against. But > the question is; what do we do when we run out? > > Will we fail clone()? That might 'surprise' quite a few people, that > their application won't work when profiled.
Or we just don't allocate any more buffers for this user; if there's a perf stream involved, we can output a record saying that. > In any case, lets focus on the other parts of this work and delay this > feature till later. Agreed. Regards, -- Alex -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
