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[86.130.134.87]) by smtp.gmail.com with ESMTPSA id z10-20020a05600c0a0a00b003a2f2bb72d5sm30633880wmp.45.2022.10.19.04.01.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Oct 2022 04:01:45 -0700 (PDT) Date: Wed, 19 Oct 2022 12:01:43 +0100 From: Qais Yousef To: John Stultz Cc: Qais Yousef , LKML , John Dias , Connor O'Brien , Rick Yiu , John Kacur , Chris Redpath , Abhijeet Dharmapurikar , Peter Zijlstra , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Thomas Gleixner , kernel-team@android.com, "J . Avila" Subject: Re: [RFC PATCH v4 3/3] softirq: defer softirq processing to ksoftirqd if CPU is busy with RT Message-ID: <20221019110143.m4romocqmprkekzw@airbuntu> References: <20221003232033.3404802-1-jstultz@google.com> <20221003232033.3404802-4-jstultz@google.com> <20221010160917.p2ftu3eezsrbfdfk@wubuntu> <20221017144455.ylmwlgrdoj3tdvbp@wubuntu> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (note the change in email) On 10/17/22 17:04, John Stultz wrote: > On Mon, Oct 17, 2022 at 7:45 AM Qais Yousef wrote: > > This time I paid attention to the average as the best case number for vanilla > > kernel is better: > > > > | vanilla | with softirq patches v4 | > > -------------------|--------------------|--------------------------| > > | #1 | #2 | #3 | #1 | #2 | #3 | > > -------------------|------|------|------|--------|--------|--------| > > t0 avg delay (us) |31.59 |22.94 |26.50 | 31.81 | 33.57 | 34.90 | > > t1 avg delay (us) |16.85 |16.32 |37.16 | 29.05 | 30.51 | 31.65 | > > t2 avg delay (us) |25.34 |32.12 |17.40 | 26.76 | 28.28 | 28.56 | > > > > It shows that we largely hover around 30us with the patches compared to 16-26us > > being more prevalent for vanilla kernels. > > > > I am not sure I can draw a concrete conclusion from these numbers. It seems > > I need to run longer than 4 hours to hit the worst case scenario every run on > > the vanilla kernel. There's an indication that the worst case scenario is > > harder to hit, and it looks there's a hit on the average delay. > > Thanks so much for running these tests and capturing these detailed numbers! > > I'll have to look further into the average case going up here. > > > I'm losing access to this system from today. I think I'll wait for more > > feedback on this RFC; and do another round of testing for longer periods of > > time once there's clearer sense this is indeed the direction we'll be going > > for. > > Do you mind sending me the script you used to run the test, and I'll > try to reproduce on some x86 hardware locally? I ran that in a personal CI setup. I basically do the following 3 in parallel 'scripts': cyclictest.sh [1]: cyclictest -t 3 -p 99 -D 3600 -i 1000 --json=cyclictest.json iperf.sh [2]: iperf -s -D iperf -c localhost -u -b 10g -t 3600 -i 1 -P 3 dd.sh [3]: while true do cyclictest_running=`ps -e | grep cyclictest || true` if [ "x$cyclictest_running" == "x" ]; then break fi # # Run dd # file="/tmp/myci.dd.file" for i in $(seq 3) do dd if=/dev/zero of=$file.$i bs=1M count=2048 & done wait rm -f $file* sleep 3 done [1] https://github.com/qais-yousef/myci-sched-tests/blob/dev/vars/run_cyclictest.groovy [2] https://github.com/qais-yousef/myci-sched-tests/blob/dev/vars/run_iperf_parallel.groovy [3] https://github.com/qais-yousef/myci-sched-tests/blob/dev/vars/run_dd_parallel.groovy Cheers -- Qais Yousef