Hello Kan and Andi, On 14.09.2018 17:57, linux-kernel-ow...@vger.kernel.org wrote: > > > On 9/14/2018 10:27 AM, Andi Kleen wrote: >> On Fri, Sep 14, 2018 at 08:39:36AM -0400, Liang, Kan wrote: >>> >>> >>> On 9/14/2018 5:22 AM, Alexey Budankov wrote: >>>> >>>> Hi Andi, >>>> >>>> On 14.09.2018 11:54, Andi Kleen wrote: >>>>>>> In principle the LBRs need to be flushed between threads. So does >>>>>>> current code. >>>>>> >>>>>> IMHO, ideally, LBRs stack would be preserved and restored when >>>>>> switching between execution stacks. That would allow implementing >>>>>> per-thread statistical call graph view in Perf tools, fully based >>>>>> on HW capabilities. It could be advantageous for some cases, in >>>>>> comparison with traditional dwarf based call graph. >>>>> >>>>> This is already supported when you use LBR call stack mode >>>>> (perf record --call-graph lbr) >>>> >>>> Which kernel versions does it make sense to try? >>>> >>> >>> The optimization for LBR call stack has been merged into 4.19. >>> commit id: 8b077e4a69bef5c4121426e99497975860191e53 >>> perf/x86/intel/lbr: Optimize context switches for the LBR call stack >> >> I think he mean support for LBR call stack in general. This has been there >> for a long time (since Haswell) Any reasonable kernel version should >> support it. >> > > Oh I see. Yes, the feature of LBR call stack was added long time ago. > But I still recommend 4.19. Because it includes a recent bug fix for LBR call > stack. > > commit id: 0592e57b24e7e05ec1f4c50b9666c013abff7017 > perf/x86/intel/lbr: Fix incomplete LBR call stack
Thanks for your support. Best regards, Alexey > > Thanks, > Kan >
