From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=148.163.156.1 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794331772; b=2BK0N/4Pep43GZ/lvogxzc9h3au/qBQDJGnlmXHIpn2SFom2pivEOoHeOyhmA5oMWpsf 0kr+xjlVJJbvgcD99q5AxXgupzydvYjqaQX0rCuM8Bgpwe1hKi1Ex3xIInBYaR/VAeEFR LwE6Pyd92CNVAFTThP1WSeaCVgHJwflx9dhhkV0L4oTCwoSgRk2V51NTZqYizJYSbK49K ZFKSpP3SARzHEzo2J3wQGXwbbW1ELFJuuoebGWOWz6BSbJOXaaZ5rhjG81O/r9RRu/Ijf 71jer+A0o7nMY1blmLw/W4dxcPhDIzlrnfXADWml2V7v8nExUZTvkaudpyRSVzDk2lA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794331772; h=DMARC-Filter:Received:DKIM-Signature:Received:Received:Received: Received:Received:Received:Received:Message-ID:Date:MIME-Version: User-Agent:Subject:To:Cc:References:From:Content-Language:In-Reply-To: Content-Type:Content-Transfer-Encoding:X-TM-AS-GCONF: X-Proofpoint-Reinject:X-Proofpoint-ORIG-GUID:X-Authority-Analysis: X-Proofpoint-GUID:X-Proofpoint-Spam-Details-Enc: X-Proofpoint-Spam-Info:X-Proofpoint-Virus-Version: X-Proofpoint-Spam-Details; bh=BpV+K+p2ba6sXSUO+GYEB1VH/bpsjyQSMt5G6lPVDWM=; b=oAlrd8dblYdB0O7ogyo5njiN/p3KmdWlYN5jkiIQRug/38Olu00pd782V/2YGSV2GL1C eZebluXo0Zc2GDQaivNmk1lA+hXim1mhp8ENhZrVLABan32lwNuQX5o2hlh5hB79I9hd4 FXWOTiL6y8EQF3ZmwKKT/wiimS+vb4GO4YPY+AN/tpX8o8gyOXbkwIkOLv5fWe/SmiMb+ VwRVHqbykc2qR7Kn0nF/TVcIGGlCD1/ELBbMcamY1p8wR8sOApoRLo4N04Kbxn4QUfUf2 KooZF03ubz9uw+4g6CJclSDqItPKaErS840fVNim9CwkoijNeAASDvs9YDDb3q9O1OA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.ibm.com; spf=pass smtp.mailfrom=linux.ibm.com; dkim=pass header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=jkGcFe6W; arc=none smtp.remote-ip=148.163.156.1 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 93877606A335 for ; Tue, 10 Nov 2026 17:29:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 93877606A335 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256 header.s=pp1 header.b=jkGcFe6W Received: from pps.filterd (m0360083.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 6AAFEXGd2865290; Tue, 10 Nov 2026 17:29:04 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=pp1; bh=BpV+K+ p2ba6sXSUO+GYEB1VH/bpsjyQSMt5G6lPVDWM=; b=jkGcFe6WcLmEhrslyWM/jl fZ5q/c1fxsRrZd3qvfrwSLckaENeoKCA6ZgTQBzCPejPzqIbSuBja41bHRQ8OtIO tZDpRNIIRIJzP9roAzIqO2RGOLHvl4yVKH2jQ1RYUY/FmtBFprRDhruFNXHQ/Rp9 cNFHTRkTEHvz+KD5Qm+1W9R6GBQVi9/YABGGlEnkwI2uLybPalIGU5c7HKdjAfhH Ek65yb07WEWZJ3RBaFXgKRgPFR8wCpXnCB3y7xq5xpLLVf9586CZzFhEco0djTwZ d23zQ6VEoQeg509GQ+cfM2vXNhqslXnaiKVcaBdbPV1LYM+/M0feNrvYlbHEKF9g == Received: from ppma12.dal12v.mail.ibm.com (dc.9e.1632.ip4.static.sl-reverse.com [50.22.158.220]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 4hsug66a48-1 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Tue, 10 Nov 2026 17:29:03 +0000 (GMT) Received: from pps.filterd (ppma12.dal12v.mail.ibm.com [127.0.0.1]) by ppma12.dal12v.mail.ibm.com (8.18.1.11/8.18.1.11) with ESMTP id 6AAF503N1925685; Tue, 10 Nov 2026 17:29:03 GMT Received: from smtprelay06.fra02v.mail.ibm.com ([9.218.2.230]) by ppma12.dal12v.mail.ibm.com (PPS) with ESMTPS id 4hv309h3n6-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 10 Nov 2026 17:29:03 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (smtpav02.fra02v.mail.ibm.com [10.20.54.101]) by smtprelay06.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 6AAHSxIU40960292 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 10 Nov 2026 17:28:59 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3D92D20043; Tue, 10 Nov 2026 17:28:59 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1288920040; Tue, 10 Nov 2026 17:28:56 +0000 (GMT) Received: from [9.39.16.14] (unknown [9.39.16.14]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 10 Nov 2026 17:28:55 +0000 (GMT) Message-ID: <77f21080-06cc-46ed-a125-d9859792ff3a@linux.ibm.com> Date: Tue, 10 Nov 2026 22:58:55 +0530 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/4] powerpc/topology: Introduce llc_override kernel parameter To: Chen Yu Cc: maddy@linux.ibm.com, linuxppc-dev@lists.ozlabs.org, peterz@infradead.org, tim.c.chen@linux.intel.com, christophe.leroy@csgroup.eu, linux-kernel@vger.kernel.org, ritesh.list@gmail.com, kprateek.nayak@amd.com, vineethr@linux.ibm.com, vincent.guittot@linaro.org, srikar@linux.ibm.com, npiggin@gmail.com, mpe@ellerman.id.au References: <20261023131646.2907938-1-sshegde@linux.ibm.com> <20261023131646.2907938-2-sshegde@linux.ibm.com> From: Shrikanth Hegde Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: 40IffSw--BjgpATlTgbsaJykScVbMuk1 X-Authority-Analysis: v=2.4 cv=PeVqFShd c=1 sm=1 tr=0 ts=6af35460 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=zJRp6_cAMcgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=0_ZDYW1gR2TTHSzkmfcA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: MGXdlJTINTHCq1qJQsHm9525lZQ5KhBh X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMTEwMDA2OCBTYWx0ZWRfXyR1QyJgTICqX LXCiAJIRWJzPqVGyLs8w0uzfOjlS7cy+Jt77PZhYhNzDUvoMufNR+vNCavGhZ4OXA+bCtN8/j4g Wj24ZOS5PxdcQLndZXh7Xd2YePn4dSTS929Fyf5Q1DJ8Q7A/Zgy1YHo5SHs5//cNVmXMN/yav6T l6vUF2F7N6b+XPNoWD6KHB3j+zx8Okzlz6XoXeB0zNIbl7SCpH1qFjyxlkXSfYSMsRCAEo0EkZM 9n4d97urm2Jgjl92sn4vJTzoqAyHhTUQPrQqWYsg1VbviMitLrh3ddmRvhrHYEnArnW8f9koimy M0aHwWjzIaJdxfnFY+QNcf7G/CKbUMxqV4N0rQcMHH9TIBvv5IMzCO3s6945rSYKL5wwNfyS1Ln /7usC1xIL7nPJXs/FuY4GTDSSwbzfZE5zk7kCQMLBGiMJWdKExr1QpWV4d6TyKFZKmMnethonwr i4kmn4oONVop6TVu/jw== X-Proofpoint-Spam-Info: AW1haW4tMjYxMTEwMDA2OCBTYWx0ZWRfX7W5EJGjTBLd4 y8GKVP6jhQLts9Z2Loz7brOIPr657hYeOwuBWJjyazJrA/m3yz6EjotX+uYdwFP5KQpSzAjEmiJ 7Wk8fsSUSF0ukHiJ0Aqkbrk5RUqEOks= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-11-10_05,2026-11-06_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 phishscore=0 suspectscore=0 impostorscore=0 priorityscore=1501 lowpriorityscore=0 spamscore=0 malwarescore=0 clxscore=1015 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2611040001 definitions=main-2611100068 Hi Chen Yu, Thanks for taking a look. On 10/23/26 9:12 PM, Chen Yu wrote: > Hi Shrikanth, > > On Fri, Oct 23, 2026 at 06:46:43PM +0530, Shrikanth Hegde wrote: > > [ ... ] > >> --- >> arch/powerpc/kernel/smp.c | 23 +++++++++++++++++++++++ >> 1 file changed, 23 insertions(+) >> >> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c >> index 6a5a5469aaae..6b1201ea3572 100644 >> --- a/arch/powerpc/kernel/smp.c >> +++ b/arch/powerpc/kernel/smp.c >> @@ -1059,6 +1059,29 @@ static bool has_coregroup_support(void) >> return coregroup_enabled; >> } >> >> +enum llc_override_values { >> + LLC_OVERRIDE_MC = 1, >> + LLC_OVERRIDE_PKG = 2, >> +}; >> + >> +static int llc_override; >> + >> +static int __init set_llc_override(char *str) >> +{ >> + if (!strcasecmp(str, "mc") && has_coregroup_support()) >> + WRITE_ONCE(llc_override, LLC_OVERRIDE_MC); > > There is only 1 booting CPU at the moment, maybe WRITE_ONCE() is not needed. Yes. > >> + else if (!strcasecmp(str, "pkg")) >> + WRITE_ONCE(llc_override, LLC_OVERRIDE_PKG); >> + else { >> + pr_warn("Unsupported llc_override=%s\n", str); >> + return 1; >> + } >> + >> + pr_info("llc_override set at domain: %s\n", str); >> + return 1; >> +} >> +__setup("llc_override=", set_llc_override); >> + >> static int __init init_big_cores(void) >> { >> int cpu; > > On PowerPC, it seems that get_effective_llc_bytes() always returns 0, > which makes exceed_llc_capacity() return true, so cache-aware scheduling > is disabled on PowerPC. We might need to provide an arch_llc_bytes() that > is adjusted based on llc_override - sometimes calculate the sum of L2 across > several cores. > > thanks, > Chenyu Ah!. I hadn't checked that. Thanks for pointing out. I am thinking right path would be to move powerpc cacheinfo into a generic one. I see there was an effort a while ago. Need to look into how to pull it off if it is possible. We could think of arch_llc_bytes if above is not possible.