Em Wed, Aug 19, 2020 at 03:46:06PM +0530, Muni Sekhar escreveu: > On Tue, Aug 18, 2020 at 11:45 PM peter enderborg <peter.enderborg@xxxxxxxx> wrote: > > On 8/18/20 7:53 PM, Muni Sekhar wrote: > > > On Tue, Aug 18, 2020 at 11:06 PM Greg KH <greg@xxxxxxxxx> wrote: > > >> On Tue, Aug 18, 2020 at 11:01:35PM +0530, Muni Sekhar wrote: > > >>> On Tue, Aug 18, 2020 at 10:44 PM Greg KH <greg@xxxxxxxxx> wrote: > > >> Those are _very_ different kernel versions, with many years and tens of > > >> thousands of different changes between them. > > >> > > >> Hopefully the newer kernel is faster, so just stick with that :) > > > But unfortunately the newer kernel is very slow, that is the reason > > > for starting this investigation :) > > > Any type of help, and guidelines to dive deeper will be highly appreciated. > > > > On the 4.4 kernel you dont have > > > > +CONFIG_RETPOLINE=y > > +CONFIG_INTEL_RDT=y > Thanks! That is helpful. Yes, I see 4.4 kernel don't have the above > two config options. > What analysis can be done to narrow down the root cause? > Any example of reference could be helpful to understand. This made me remember Lisbon: http://vger.kernel.org/~acme/perf/bpf-is-eating-the-world-dont-you-see-lpc-lisbon-2019/#/8/2 Greg was there when this slide was first shown... ;-) Look at the icache misses when the kernel is entered (syscall entry). Then add this to the kernel command line: "nospectre_v1 nospectre_v2" And see what happens: http://vger.kernel.org/~acme/perf/bpf-is-eating-the-world-dont-you-see-lpc-lisbon-2019/#/8/3 So using these (and any new ones related to disabling hardware flaw mitigation) maybe a way to analyse this, if you haven't figured this out yet, sorry for the huge delay in replying 8-) - Arnaldo > > > > And your base is very different two. > > > > Try to use mainline on both system and see. > > > > You can also use the same base kernel version from ubuntu and > > > > run your test. > > > > > > >> greg k-h > > > > > > > > > > > -- > Thanks, > Sekhar -- - Arnaldo _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
