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Mon, 7 Jul 2025 09:38:11 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2020620040; Mon, 7 Jul 2025 09:38:11 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 21E3E2004E; Mon, 7 Jul 2025 09:38:09 +0000 (GMT) Received: from [9.109.215.252] (unknown [9.109.215.252]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 7 Jul 2025 09:38:08 +0000 (GMT) Message-ID: <49a9e43b-7ca5-4c90-a8b2-c43a84c34aeb@linux.ibm.com> Date: Mon, 7 Jul 2025 15:08:08 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 00/12] sched: Address schbench regression To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, clm@meta.com References: <20250702114924.091581796@infradead.org> <132949bc-f901-40e6-a34c-d1d67d03d8b6@linux.ibm.com> <20250707091136.GB1099709@noisy.programming.kicks-ass.net> From: Shrikanth Hegde Content-Language: en-US In-Reply-To: <20250707091136.GB1099709@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNzA3MDA1MyBTYWx0ZWRfX2RRJXdpsRtS+ DlHhzO0OLPcGi0oLDXbAe7RNjv5l49lMAVxjFKjgG8+jp+e3NClv0j44VaPCNpRZBWbweN+qhhy iVy1UWtKyWDcuBwBIcM75UV0WNHkc8mRxOjGec7M2xQYjhrmi5GdUaR6weAkr2v++KHokXjtVFj CkiOyLWt6H2xlC4btN6bZxwYElIXDy+BquvsuKdCXdNfrf7mGqnH17xzlr2Ejl5h7GXv/ANv485 U4KZzk6uKL1gqhp0INeH+3sraOqJqNl7XPZXmbiv0z4pfzqdVNfqUTZRe2/o7PHBMueD9l6hHRl bQI1Jz9uioJhUAWHn6NewP1hMPV8Jl6hW4KX0Q48J1WC+YtSLuI0Ju9XJXlRmVFUdT563QI+IwA nK3Q/zGOGmTD7uckX/hMqEcPwPm1/ktosZRbEI7+drekZvbnaX9GIS53EvOcGQP+8m9CW/Bq X-Proofpoint-GUID: Jx6BoolNriS9tgqYUbK53f8_IN8epa4n X-Proofpoint-ORIG-GUID: vdm6K6pcJLTCNEl7nNtgLJ7sYLnjIStB X-Authority-Analysis: v=2.4 cv=W/M4VQWk c=1 sm=1 tr=0 ts=686b9586 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=Wb1JkmetP80A:10 a=VwQbUJbxAAAA:8 a=JfrnYn6hAAAA:8 a=0YX1pDHftsOKNYb_5vcA:9 a=QEXdDO2ut3YA:10 a=1CNFftbPRP8L7MoqJWF3:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.7,FMLib:17.12.80.40 definitions=2025-07-07_01,2025-07-07_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 phishscore=0 mlxscore=0 priorityscore=1501 adultscore=0 clxscore=1015 suspectscore=0 spamscore=0 lowpriorityscore=0 mlxlogscore=384 bulkscore=0 impostorscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505280000 definitions=main-2507070053 On 7/7/25 14:41, Peter Zijlstra wrote: > On Mon, Jul 07, 2025 at 02:35:38PM +0530, Shrikanth Hegde wrote: >> >> >> On 7/2/25 17:19, Peter Zijlstra wrote: >>> Hi! >>> >>> Previous version: >>> >>> https://lkml.kernel.org/r/20250520094538.086709102@infradead.org >>> >>> >>> Changes: >>> - keep dl_server_stop(), just remove the 'normal' usage of it (juril) >>> - have the sched_delayed wake list IPIs do select_task_rq() (vingu) >>> - fixed lockdep splat (dietmar) >>> - added a few preperatory patches >>> >>> >>> Patches apply on top of tip/master (which includes the disabling of private futex) >>> and clm's newidle balance patch (which I'm awaiting vingu's ack on). >>> >>> Performance is similar to the last version; as tested on my SPR on v6.15 base: >>> >> >> >> Hi Peter, >> Gave this a spin on a machine with 5 cores (SMT8) PowerPC system. >> >> I see significant regression in schbench. let me know if i have to test different >> number of threads based on the system size. >> Will go through the series and will try a bisect meanwhile. > > Urgh, those are terrible numbers :/ > > What do the caches look like on that setup? Obviously all the 8 SMT > (is this the supercore that glues two SMT4 things together for backwards > compat?) share some cache, but is there some shared cache between the > cores? It is a supercore(we call it as bigcore) which glues two SMT4 cores. LLC is per SMT4 core. So from scheduler perspective system is 10 cores (SMT4)