Messages in this thread |  | | | From | Linus Torvalds <> | | Date | Tue, 3 Aug 2010 13:02:59 -0700 | | Subject | Re: [patch 1/2] x86_64 page fault NMI-safe |
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On Tue, Aug 3, 2010 at 12:45 PM, Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote: > > The real issue here, IMHO, is that Perf has tied gory ring buffer implementation > details to the userspace perf ABI, and there is now strong unwillingness from > Perf developers to break this ABI.
The thing is - I think my outlined buffer fragmentation model would work fine with the perf ABI too. Exactly because there is no deep structure, just the same "stream of small events" both from a kernel and a user model standpoint. Sure, the stream would now contain a new event type, but that's trivial. It would still be _entirely_ reasonable to have the actual data in the exact same ring buffer, including the whole mmap'ed area.
Of course, when user space actually parses it, user space would have to eventually defragment the event by allocating a new area and copying the fragments together in the right order, but that's pretty trivial to do. It certainly doesn't affect the current mmap'ed interface in the least.
Now, whether the perf people feel they want that kind of functionality, I don't know. It's possible that they simply do not want to handle events that are complex enough that they would have arbitrary size.
Linus
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