Messages in this thread |  | | Date | Wed, 22 Oct 2014 15:15:53 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: perf: Translating mmap2 ids into socket info? |
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Em Wed, Oct 22, 2014 at 02:42:26PM -0300, Arnaldo Carvalho de Melo escreveu: > Em Wed, Oct 22, 2014 at 06:45:10PM +0200, Peter Zijlstra escreveu: > > On Wed, Oct 22, 2014 at 12:20:26PM -0400, Don Zickus wrote: > > > Our cache-to-cache tool noticed the slowdown but we couldn't understand > > > why because we had falsely assumed the memory was allocated on the local > > > node but instead it was on the remote node.
> > But in general, you can never say for user memory, since that has the > > process page table mapping in between, the user virtual address is > > unrelated to backing (and can change frequently and without > > notification).
> > Therefore the mmap(2) information is useless for this, it only concerns > > user memory.
> So what you are saying is that it is difficult to have some sort of > mechanism that an mmap moved from one node to another, when that > happens, i.e. a new tracepoint for that?
Humm, so, after reading a bit more, I see that we can figure out which ranges are in which NUMA nodes (like shown in dmesg), and we have the phys addr, so is this just a matter of perf tooling complement the information the kernel provides on mmap2 (and the hardware provides on those events)?
- Arnaldo
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