Messages in this thread | | | Date | Wed, 22 Oct 2014 21:55:35 +0200 | From | Peter Zijlstra <> | Subject | Re: perf: Translating mmap2 ids into socket info? |
| |
On Wed, Oct 22, 2014 at 03:15:53PM -0300, Arnaldo Carvalho de Melo wrote: > 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)?
We explicitly do not expose the phys address of user space pages. So nope.
| |