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SubjectRe: [LKP] [net] 19f92a030c: apachebench.requests_per_second -37.9% regression
Hi Eric,

On Wed, Nov 13, 2019 at 06:33:44AM -0800, Eric Dumazet wrote:
> On Wed, Nov 13, 2019 at 2:35 AM Feng Tang <feng.tang@intel.com> wrote:
> >
> > Hi Eric,
> >
> > On Fri, Nov 08, 2019 at 04:35:13PM +0800, kernel test robot wrote:
> > > Greeting,
> > >
> > > FYI, we noticed a -37.9% regression of apachebench.requests_per_second due to commit:
> > >
> > > commit: 19f92a030ca6d772ab44b22ee6a01378a8cb32d4 ("net: increase SOMAXCONN to 4096")
> > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> >
> > Any thought on this? The test is actually:
> >
> > sysctl -w net.ipv4.tcp_syncookies=0
>
>
> I have no plan trying to understand why anyone would disable syncookies .
> This is a non starter really, since this makes a server vulnerable to
> a trivial DOS attack.
>

Thanks for the prompt response.

This sysctl change was added to work around one old error when
running the apachebench. The error was "apr_socket_recv: Connection
reset by peer (104)"

I just removed the sysctl setting of "ipv4.tcp_synccookies" and
re-run the same benchmark in 0day, the regression is still there.

Thanks,
Feng

>
> Since the test changes a sysctl, you also can change other sysctls if
> you really need to show a ' number of transactions' for a particular
> benchmark.
>
> The change on SOMAXCONN was driven by a security issue, and security
> comes first.
>
>
> > enable_apache_mod auth_basic authn_core authn_file authz_core authz_host authz_user access_compat
> > systemctl restart apache2
> > ab -k -q -t 300 -n 1000000 -c 4000 127.0.0.1/
> >
> > And some info about apachebench result is:
> >
> > w/o patch:
> >
> > Connection Times (ms)
> > min mean[+/-sd] median max
> > Connect: 0 0 19.5 0 7145
> > Processing: 0 4 110.0 3 21647
> > Waiting: 0 2 92.4 1 21646
> > Total: 0 4 121.1 3 24762
> >
> > w/ patch:
> >
> > Connection Times (ms)
> > min mean[+/-sd] median max
> > Connect: 0 0 43.2 0 7143
> > Processing: 0 19 640.4 3 38708
> > Waiting: 0 24 796.5 1 38708
> > Total: 0 19 657.5 3 39725
> >
> >
> > Thanks,
> > Feng
> >
> > >
> > > in testcase: apachebench
> > > on test machine: 16 threads Intel(R) Xeon(R) CPU D-1541 @ 2.10GHz with 48G memory
> > > with following parameters:
> > >
> > > runtime: 300s
> > > concurrency: 4000
> > > cluster: cs-localhost
> > > cpufreq_governor: performance
> > > ucode: 0x7000019
> > >
> > > test-description: apachebench is a tool for benchmarking your Apache Hypertext Transfer Protocol (HTTP) server.
> > > test-url: https://httpd.apache.org/docs/2.4/programs/ab.html
> > >
> > > In addition to that, the commit also has significant impact on the following tests:
> > >
> > > +------------------+------------------------------------------------------------------+
> > > | testcase: change | apachebench: apachebench.requests_per_second -37.5% regression |
> > > | test machine | 16 threads Intel(R) Xeon(R) CPU D-1541 @ 2.10GHz with 48G memory |
> > > | test parameters | cluster=cs-localhost |
> > > | | concurrency=8000 |
> > > | | cpufreq_governor=performance |
> > > | | runtime=300s |
> > > | | ucode=0x7000019 |
> > > +------------------+------------------------------------------------------------------+
> > >
> > >
> > > If you fix the issue, kindly add following tag
> > > Reported-by: kernel test robot <rong.a.chen@intel.com>
> > >
> > >
> > > Details are as below:
> > > -------------------------------------------------------------------------------------------------->
> > >
> > >
> > > To reproduce:
> > >
> > > git clone https://github.com/intel/lkp-tests.git
> > > cd lkp-tests
> > > bin/lkp install job.yaml # job file is attached in this email
> > > bin/lkp run job.yaml
> > >
> > > =========================================================================================
> > > cluster/compiler/concurrency/cpufreq_governor/kconfig/rootfs/runtime/tbox_group/testcase/ucode:
> > > cs-localhost/gcc-7/4000/performance/x86_64-rhel-7.6/debian-x86_64-2019-09-23.cgz/300s/lkp-bdw-de1/apachebench/0x7000019
> > >
> > > commit:
> > > 6d6f0383b6 ("netdevsim: Fix use-after-free during device dismantle")
> > > 19f92a030c ("net: increase SOMAXCONN to 4096")
> > >
> > > 6d6f0383b697f004 19f92a030ca6d772ab44b22ee6a
> > > ---------------- ---------------------------
> > > %stddev %change %stddev
> > > \ | \
> > > 22640 ± 4% +71.1% 38734 apachebench.connection_time.processing.max
> > > 24701 +60.9% 39743 apachebench.connection_time.total.max
> > > 22639 ± 4% +71.1% 38734 apachebench.connection_time.waiting.max
> > > 24701 +15042.0 39743 apachebench.max_latency.100%
> > > 40454 -37.9% 25128 apachebench.requests_per_second
> > > 25.69 +58.8% 40.79 apachebench.time.elapsed_time
> > > 25.69 +58.8% 40.79 apachebench.time.elapsed_time.max
> > > 79.00 -37.0% 49.75 apachebench.time.percent_of_cpu_this_job_got
> > > 98.88 +61.0% 159.18 apachebench.time_per_request
> > > 434631 -37.9% 269889 apachebench.transfer_rate
> > > 1.5e+08 ± 18% +109.5% 3.141e+08 ± 27% cpuidle.C3.time
> > > 578957 ± 7% +64.1% 949934 ± 12% cpuidle.C3.usage
> > > 79085 ± 4% +24.8% 98720 meminfo.AnonHugePages
> > > 41176 +14.2% 47013 meminfo.PageTables
> > > 69429 -34.9% 45222 meminfo.max_used_kB
> > > 63.48 +12.7 76.15 mpstat.cpu.all.idle%
> > > 2.42 ± 2% -0.9 1.56 mpstat.cpu.all.soft%
> > > 15.30 -5.2 10.13 mpstat.cpu.all.sys%
> > > 18.80 -6.6 12.16 mpstat.cpu.all.usr%
> > > 65.00 +17.7% 76.50 vmstat.cpu.id
> > > 17.00 -35.3% 11.00 vmstat.cpu.us
> > > 7.00 ± 24% -50.0% 3.50 ± 14% vmstat.procs.r
> > > 62957 -33.3% 42012 vmstat.system.cs
> > > 33174 -1.4% 32693 vmstat.system.in

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