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

[Oliver Sang]

hi, Frederic Weisbecker,


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 :
> > 
> > 
> > Hello,
> > 
> > kernel test robot noticed a -1.2% regression of netperf.Throughput_Mbps on:
> > 
> > 
> > commit: 7ee988770326fca440472200c3eb58935fe712f6 ("timers: Implement the hierarchical pull model")
> > https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git timers/core
> > 
> > testcase: netperf
> > test machine: 128 threads 2 sockets Intel(R) Xeon(R) Gold 6338 CPU @ 2.00GHz (Ice Lake) with 256G memory
> > parameters:
> > 
> > 	ip: ipv4
> > 	runtime: 300s
> > 	nr_threads: 200%
> > 	cluster: cs-localhost
> > 	test: SCTP_STREAM
> > 	cpufreq_governor: performance
> > 
> > 
> > 
> > 
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
> > | Closes: https://lore.kernel.org/oe-lkp/202403011511.24defbbd-oliver.sang@xxxxxxxxx
> > 
> > 
> > Details are as below:
> > -------------------------------------------------------------------------------------------------->
> > 
> > 
> > The kernel config and materials to reproduce are available at:
> > https://download.01.org/0day-ci/archive/20240301/202403011511.24defbbd-oliver.sang@xxxxxxxxx
> > 
> > =========================================================================================
> > 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: 
> >   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


> 
> 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

though it seems irelevant, we will still get data for it.

> 
> Thanks.