On 10/8/13 1:54 PM, Stephane Eranian wrote:
If the current MMAP2 is not a complete solution for what you (Google)
need, should support be reverted before 3.12 is released? No sense in
making this part of the forever API if more work is needed on it.
Instead of a full revert we could just turn off the ABI portion minimally
and not recognize it for now. Assuming a more complete solution is in the
works for v3.13.
That's a possibility. They are also pieces in the perf tool itself.
We could certainly make the attr->mmap2 bit disappear.
I think it boils down to how can we uniquely identify virtual
mapping to the same physical data either via shmat(), files, VM_CLONE.
We had all covered but the last case with the ino approach. We don't have
a solution for VM_CLONE yet.
I was mainly thinking the 2 parts that generate MMAP2 events: kernel
side it's the mmap2 attribute and perf_event_mmap_output; userspace side
it's perf_event__synthesize_mmap_event. Certainly the rest of the
plumbing can be left in place until the solution is refined as needed.
David
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