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Thu, 10 Aug 2023 15:44:07 +0000 (GMT) Message-ID: <5f0824ea-d7b6-61f5-db89-1727bae83595@linux.vnet.ibm.com> Date: Thu, 10 Aug 2023 21:14:06 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.14.0 Subject: Re: [RFC PATCH] sched/fair: Skip idle CPU search on busy system Content-Language: en-US To: Vishal Chourasia Cc: peterz@infradead.org, vincent.guittot@linaro.org, srikar@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, mingo@redhat.com, dietmar.eggemann@arm.com, mgorman@suse.de References: <20230726093612.1882644-1-sshegde@linux.vnet.ibm.com> From: Shrikanth Hegde In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: oCVD6jSkQr3lqVIlFs-O0QqD2ojgDMD5 X-Proofpoint-GUID: ulfyZEnMV22GL6WENHfF2GG9pfeJzM90 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.267,Aquarius:18.0.957,Hydra:6.0.591,FMLib:17.11.176.26 definitions=2023-08-10_13,2023-08-10_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 mlxlogscore=789 adultscore=0 suspectscore=0 priorityscore=1501 bulkscore=0 malwarescore=0 impostorscore=0 phishscore=0 lowpriorityscore=0 mlxscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2306200000 definitions=main-2308100133 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/10/23 12:14 AM, Vishal Chourasia wrote: > On Wed, Jul 26, 2023 at 03:06:12PM +0530, Shrikanth Hegde wrote: >> When the system is fully busy, there will not be any idle CPU's. >> > Tested this patchset on top of v6.4 [...] > 5 Runs of stress-ng (100% load) on a system with 16CPUs spawning 23 threads for > 60 minutes. > > stress-ng: 16CPUs, 23threads, 60mins > > - 6.4.0 > > | completion time(sec) | user | sys | > |----------------------+-----------+------------| > | 3600.05 | 57582.44 | 0.70 | > | 3600.10 | 57597.07 | 0.68 | > | 3600.05 | 57596.65 | 0.47 | > | 3600.04 | 57596.36 | 0.71 | > | 3600.06 | 57595.32 | 0.42 | > | 3600.06 | 57593.568 | 0.596 | average > | 0.046904158 | 12.508392 | 0.27878307 | stddev > > - 6.4.0+ (with patch) > > | completion time(sec) | user | sys | > |----------------------+-----------+-------------| > | 3600.04 | 57596.58 | 0.50 | > | 3600.04 | 57595.19 | 0.48 | > | 3600.05 | 57597.39 | 0.49 | > | 3600.04 | 57596.64 | 0.53 | > | 3600.04 | 57595.94 | 0.43 | > | 3600.042 | 57596.348 | 0.486 | average > | 0.0089442719 | 1.6529610 | 0.072938330 | stddev > > The average system time is slightly lower in the patched version (0.486 seconds) > compared to the 6.4.0 version (0.596 seconds). > The standard deviation for system time is also lower in the patched version > (0.0729 seconds) than in the 6.4.0 version (0.2788 seconds), suggesting more > consistent system time results with the patch. > > vishal.c Thank you very much Vishal for trying this out. Meanwhile, I am yet to try the suggestion given by chen. Let me see if that works okay.