Re: [tip:timers/core] [timers] 7ee9887703: netperf.Throughput_Mbps -1.2% regression

[Frederic Weisbecker]

On Tue, Mar 05, 2024 at 10:17:43AM +0800, Oliver Sang wrote:
> hi, Frederic Weisbecker,
> 
> On Mon, Mar 04, 2024 at 12:28:33PM +0100, Frederic Weisbecker wrote:
> > Le Mon, Mar 04, 2024 at 10:13:00AM +0800, Oliver Sang a écrit :
> > > On Mon, Mar 04, 2024 at 01:32:45AM +0100, Frederic Weisbecker wrote:
> > > > Le Fri, Mar 01, 2024 at 04:09:24PM +0800, kernel test robot a écrit :
> > > > > commit: 
> > > > >   57e95a5c41 ("timers: Introduce function to check timer base is_idle flag")
> > > > >   7ee9887703 ("timers: Implement the hierarchical pull model")
> > > > 
> > > > Is this something that is observed also with the commits that follow in this
> > > > branch?
> > > 
> > > when this bisect done, we also tested the tip of timers/core branch at that time
> > > 8b3843ae3634b vdso/datapage: Quick fix - use asm/page-def.h for ARM64
> > > 
> > > the regression still exists on it:
> > > 
> > > 57e95a5c4117dc6a 7ee988770326fca440472200c3e 8b3843ae3634b472530fb69c386
> > > ---------------- --------------------------- ---------------------------
> > >          %stddev     %change         %stddev     %change         %stddev
> > >              \          |                \          |                \
> > >       4.10            -1.2%       4.05            -1.2%       4.05        netperf.ThroughputBoth_Mbps
> > >       1049            -1.2%       1037            -1.2%       1036        netperf.ThroughputBoth_total_Mbps
> > >       4.10            -1.2%       4.05            -1.2%       4.05        netperf.Throughput_Mbps
> > >       1049            -1.2%       1037            -1.2%       1036        netperf.Throughput_total_Mbps
> > 
> > Oh, I see... :-/
> > 
> > > > Ie: would it be possible to compare instead:
> > > > 
> > > >     57e95a5c4117 (timers: Introduce function to check timer base is_idle flag)
> > > > VS
> > > >     b2cf7507e186 (timers: Always queue timers on the local CPU)
> > > > 
> > > > Because the improvements introduced by 7ee9887703 are mostly relevant after
> > > > b2cf7507e186.
> > > 
> > > got it. will test.
> > > 
> > > at the same time, we noticed current tip of timers/core is
> > > a184d9835a0a6 (tip/timers/core) tick/sched: Fix build failure for
> > > CONFIG_NO_HZ_COMMON=n
> > 
> > Shouldn't be a problem as it fixes an issue introduced after:
> > 
> > 	  b2cf7507e186 (timers: Always queue timers on the local CPU)
> > 
> > > 
> > > though it seems irelevant, we will still get data for it.
> > 
> > Thanks a lot, this will be very helpful. Especially with all the perf diff
> > details like in the initial email report.
> 
> the regression still exists on b2cf7507e186 and current tip of the branch:
> 
> =========================================================================================
> cluster/compiler/cpufreq_governor/ip/kconfig/nr_threads/rootfs/runtime/tbox_group/test/testcase:
>   cs-localhost/gcc-12/performance/ipv4/x86_64-rhel-8.3/200%/debian-12-x86_64-20240206.cgz/300s/lkp-icl-2sp2/SCTP_STREAM/netperf
> 
> commit:
>   57e95a5c4117 (timers: Introduce function to check timer base is_idle flag)
>   b2cf7507e186 (timers: Always queue timers on the local CPU)
>   a184d9835a0a (tick/sched: Fix build failure for CONFIG_NO_HZ_COMMON=n)
>   
>   a184d9835a0a689261ea6a4a8dbc18173a031b77
> 
> 57e95a5c4117dc6a b2cf7507e18649a30512515ec0c a184d9835a0a689261ea6a4a8db
> ---------------- --------------------------- ---------------------------
>          %stddev     %change         %stddev     %change         %stddev
>              \          |                \          |                \
>       4.10            -1.4%       4.04            -1.5%       4.04        netperf.ThroughputBoth_Mbps
>       1049            -1.4%       1034            -1.5%       1033        netperf.ThroughputBoth_total_Mbps
>       4.10            -1.4%       4.04            -1.5%       4.04        netperf.Throughput_Mbps
>       1049            -1.4%       1034            -1.5%       1033        netperf.Throughput_total_Mbps
> 
> details are in below [1]

Thanks a lot!

> 
> > Because I'm having some troubles
> > running those lkp tests. How is it working BTW? I've seen it downloading
> > two kernel trees but I haven't noticed a kernel build.
> 
> you need build 7ee9887703 and its parent kernel with config in
> https://download.01.org/0day-ci/archive/20240301/202403011511.24defbbd-oliver.sang@xxxxxxxxx
> then boot into kernel.
> 
> after that, you could run netperf in each kernel by following
> https://download.01.org/0day-ci/archive/20240301/202403011511.24defbbd-oliver.sang@xxxxxxxxx/reproduce
> to get data.
> 
> the results will store in different path according the kernel commit, then you
> could compare the results from both kernels.

Oh I see now.

> 
> what's your OS BTW? we cannot support all distributions so far...

Opensuse, but it failed to find a lot of equivalent packages.
Then I tried Ubuntu 22.04.4 LTS but it failed saying perf didn't have the
"sched" subcommand. Which distro do you recommand using?

> 
> > Are the two compared
> > instances running through kvm?
> 
> we run performance tests on bare mental. for netperf, we just test on one
> machine so the test is really upon local net.

Ok.

Thanks!