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@sony.com> wrote:
On 8/18/20 7:53 PM, Muni Sekhar wrote:
On Tue, Aug 18, 2020 at 11:06 PM Greg KH <greg@kroah.com> 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@kroah.com> 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-l... 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-l... 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