From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9700B2FCC1E for ; Wed, 15 Oct 2025 21:28:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.10 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760563732; cv=none; b=tuGBuj7OTduUpFILMFrnq1p3zJq8mGuX7I47OyW5hWu/XU+XiMgwHKtZMEiRNOmoi+mHaWw85++U8kJ//qmYCdToHZW7NZSCQrEkdE7tB3L8PunfEZzhpFUxWA9N7Y3qZfHG7yPbkFN4Gqh7lIHAGkdeL+Xd+FO6ZwxCPixgBJE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760563732; c=relaxed/simple; bh=R9vohPS2BBtOxX3RpJ4qxrYpZ/2/ANHFYVGLcZzfodc=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=Qm97FYFIrBzwRgABXbsO3iEyEhQ74eiFxoi0WQo1F1OzrTJanTCQNo4p1CJUWY9j0EvSWZCoka2DWCCvLipfAjPAlrfz0rQhhsX5p+xuLzlpgMU9QTTWXM2kSKBG5ubJMNvQxM3Eqcr6jFyz3PyYibN+NsRV/6kbdDa6XouTs80= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=KAvEdUwX; arc=none smtp.client-ip=198.175.65.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="KAvEdUwX" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1760563731; x=1792099731; h=message-id:subject:from:to:cc:date:in-reply-to: references:content-transfer-encoding:mime-version; bh=R9vohPS2BBtOxX3RpJ4qxrYpZ/2/ANHFYVGLcZzfodc=; b=KAvEdUwXQ4as0cwv12KiwuZzCYrbVb39Z25mnySE6k0XJMssQ+DqiQVO X/QRPwlLmZoNZKWkayO+vox45calecvpvLAZsl5lI1sHdS7ZUzoeaaJ06 4dMda/k8Hu9cXUPLro+WZLnREsJIgoud/rueD7KdeON9korFsrHa5NgSU TxAyExVOv9fhi739M7MZNRVYQio7n02B6ETu2xnsogCcBq5cqArEH3xba uaoKUG5U10xI7w/xmhGY7kLc14UIhG27tR/flI0dhwXexu7fZ+l1kSxYk nrtCOm+JenP5sOkxjEcHUgVyCYksTgiuAEt5KyG9ndQl0pFuwwoF5Up8/ w==; X-CSE-ConnectionGUID: S9Nlg5jkT2GBvrU/3jF2RQ== X-CSE-MsgGUID: 09ehyJy0SduLFoVHehwMWA== X-IronPort-AV: E=McAfee;i="6800,10657,11583"; a="80190342" X-IronPort-AV: E=Sophos;i="6.19,232,1754982000"; d="scan'208";a="80190342" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by orvoesa102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Oct 2025 14:28:50 -0700 X-CSE-ConnectionGUID: el/pq+I7RuCIycDgXejBfQ== X-CSE-MsgGUID: fidZC/UWRQaskikhwdT0mQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.19,232,1754982000"; d="scan'208";a="182266913" Received: from unknown (HELO [10.241.242.248]) ([10.241.242.248]) by orviesa008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Oct 2025 14:28:49 -0700 Message-ID: <69796d7945578a89da6d682a2478f9e238659a79.camel@linux.intel.com> Subject: Re: [PATCH 10/19] sched/fair: Prioritize tasks preferring destination LLC during balancing From: Tim Chen To: Peter Zijlstra Cc: Ingo Molnar , K Prateek Nayak , "Gautham R . Shenoy" , Vincent Guittot , Juri Lelli , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Madadi Vineeth Reddy , Hillf Danton , Shrikanth Hegde , Jianyong Wu , Yangyu Chen , Tingyin Duan , Vern Hao , Len Brown , Aubrey Li , Zhao Liu , Chen Yu , Chen Yu , Libo Chen , Adam Li , Tim Chen , linux-kernel@vger.kernel.org Date: Wed, 15 Oct 2025 14:28:49 -0700 In-Reply-To: <20251015150846.GB3168635@noisy.programming.kicks-ass.net> References: <20251015150846.GB3168635@noisy.programming.kicks-ass.net> Autocrypt: addr=tim.c.chen@linux.intel.com; prefer-encrypt=mutual; keydata=mQENBE6N6zwBCADFoM9QBP6fLqfYine5oPRtaUK2xQavcYT34CBnjTlhbvEVMTPlNNzE5 v04Kagcvg5wYcGwr3gO8PcEKieftO+XrzAmR1t3PKxlMT1bsQdTOhKeziZxh23N+kmA7sO/jnu/X2 AnfSBBw89VGLN5fw9DpjvU4681lTCjcMgY9KuqaC/6sMbAp8uzdlue7KEl3/D3mzsSl85S9Mk8KTL MLb01ILVisM6z4Ns/X0BajqdD0IEQ8vLdHODHuDMwV3veAfnK5G7zPYbQUsK4+te32ruooQFWd/iq Rf815j6/sFXNVP/GY4EWT08UB129Kzcxgj2TEixe675Nr/hKTUVKM/NrABEBAAGJAS4EIAECABgFA k6ONYoRHQFLZXkgaXMgcmVwbGFjZWQACgkQHH3vaoxLv2UmbAgAsqa+EKk2yrDc1dEXbZBBGeCiVP XkP7iajI/FiMVZHFQpme4vpntWhg0BIKnF0OSyv0wgn3wzBWx0Zh3cve/PICIj268QvXkb0ykVcIo RnWwBeavO4dd304Mzhz5fBzJwjYx06oabgUmeGawVCEq7UfXy+PsdQdoTabsuD1jq0MbOL/4sB6CZ c4V2mQbW4+Js670/sAZSMj0SQzK9CQyQdg6Wivz8GgTBjWwWsfMt4g2u0s6rtBo8NUZG/yw6fNdao DaT/OCHuBopGmsmFXInigwOXsjyp15Yqs/de3S2Nu5NdjJUwmN1Qd1bXEc/ItvnrFB0RgoNt2gzf2 5aPifLabQlVGltIENoZW4gPHRpbS5jLmNoZW5AbGludXguaW50ZWwuY29tPokBOAQTAQIAIgUCTo3 rPAIbAwYLCQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQHH3vaoxLv2XYdAf8DgRO4eIAtWZy4zLv 0EZHWiJ35GYAQ5fPFWBoNURE0+vICrvLyfCKTlUTFxFxTiAWHUO7JM+uBHQSJVsE+ERmTPsiUO1m7 SxZakGy9U2WOEiWMZMRp7HZE8vPUY5AM1OD0b38WBeUD3FPx5WRlQ0z6izF9aIHxoQhci0/WtmGLO Pw3HUlCy1c4DDl6cInpy/JqUPcYlvsp+bWbdm7R5b33WW2CNVVr1eLj+1UP0Iow4jlLzNLW+jOpiv LDs3G/bNC1Uu/SAzTvbaDBRRO9ToX5rlg3Zi8PmOUXWzEfO6N+L1gFCAdYEB4oSOghSbk2xCC4DRl UTlYoTJCRsjusXEy4ZkCDQROjjboARAAtXPJWkNkK3s22BXrcK8w9L/Kzqmp4+V9Y5MkkK94Zv66l XAybnXH3UjL9ATQgo7dnaHxcVX0S9BvHkEeKqEoMwxg86Bb2tzY0yf9+E5SvTDKLi2O1+cd7F3Wba 1eM4Shr90bdqLHwEXR90A6E1B7o4UMZXD5O3MI013uKN2hyBW3CAVJsYaj2s9wDH3Qqm4Xe7lnvTA GV+zPb5Oj26MjuD4GUQLOZVkaA+GX0TrUlYl+PShJDuwQwpWnFbDgyE6YmlrWVQ8ZGFF/w/TsRgJM ZqqwsWccWRw0KLNUp0tPGig9ECE5vy1kLcMdctD+BhjF0ZSAEBOKyuvQQ780miweOaaTsADu5MPGk d3rv7FvKdNencd+G1BRU8GyCyRb2s6b0SJnY5mRnE3L0XfEIJoTVeSDchsLXwPLJy+Fdd2mTWQPXl nforgfKmX6BYsgHhzVsy1/zKIvIQey8RbhBp728WAckUvN47MYx9gXePW04lzrAGP2Mho+oJfCpI0 myjpI9CEctvJy4rBXRgb4HkK72i2gNOlXsabZqy46dULcnrMOsyCXj6B1CJiZbYz4xb8n5LiD31SA fO5LpKQe/G4UkQOZgt+uS7C0Zfp61+0mrhKPG+zF9Km1vaYNH8LIsggitIqE05uCFi9sIgwez3oiU rFYgTkTSqMQNPdweNgVhSUAEQEAAbQ0VGltIENoZW4gKHdvcmsgcmVsYXRlZCkgPHRpbS5jLmNoZW 5AbGludXguaW50ZWwuY29tPokCVQQTAQgAPwIbAwYLCQgHAwIGFQgCCQoLBBYCAwECHgECF4AWIQT RofI2lb24ozcpAhyiZ7WKota4SQUCYjOVvwUJF2fF1wAKCRCiZ7WKota4SeetD/4hztE+L/Z6oqIY lJJGgS9gjV7c08YH/jOsiX99yEmZC/BApyEpqCIs+RUYl12hwVUJc++sOm/p3d31iXvgddXGYxim0 0+DIhIu6sJaDzohXRm8vuB/+M/Hulv+hTjSTLreAZ9w9eYyqffre5AlEk/hczLIsAsYRsqyYZgjfX Lk5JN0L7ixsoDRQ5syZaY11zvo3LZJX9lTw0VPWlGeCxbjpoQK91CRXe9dx/xH/F/9F203ww3Ggt4 VlV6ZNdl14YWGfhsiJU2rbeJ930sUDbMPJqV60aitI93LickNG8TOLG5QbN9FzrOkMyWcWW7FoXwT zxRYNcMqNVQbWjRMqUnN6PXCIvutFLjLF6FBe1jpk7ITlkS1FvA2rcDroRTU/FZRnM1k0K4GYYYPj 11Zt3ZBcPoI0J3Jz6P5h6fJioqlhvZiaNhYneMmfvZAWJ0yv+2c5tp2aBmKsjmnWecqvHL5r/bXez iKRdcWyXqrEEj6OaJr3S4C0MIgGLteARvbMH+3tNTDIqFuyqdzHLKwEHuvKxHzYFyV7I5ZEQ2HGH5 ZRZ2lRpVjSIlnD4L1PS6Bes+ALDrWqksbEuuk+ixFKKFyIsntIM+qsjkXseuMSIG5ADYfTla9Pc5f VpWBKX/j0MXxdQsxT6tiwE7P+osbOMwQ6Ja5Qi57hj8jBRF1znDjDZkBDQRcCwpgAQgAl12VXmQ1X 9VBCMC+eTaB0EYZlzDFrW0GVmi1ii4UWLzPo0LqIMYksB23v5EHjPvLvW/su4HRqgSXgJmNwJbD4b m1olBeecIxXp6/S6VhD7jOfi4HACih6lnswXXwatzl13OrmK6i82bufaXFFIPmd7x7oz5Fuf9OQlL OnhbKXB/bBSHXRrMCzKUJKRia7XQx4gGe+AT6JxEj6YSvRT6Ik/RHpS/QpuOXcziNHhcRPD/ZfHqJ SEa851yA1J3Qvx1KQK6t5I4hgp7zi3IRE0eiObycHJgT7nf/lrdAEs7wrSOqIx5/mZ5eoKlcaFXiK J3E0Wox6bwiBQXrAQ/2yxBxVwARAQABtCVUaW0gQ2hlbiA8dGltLmMuY2hlbkBsaW51eC5pbnRlbC 5jb20+iQFUBBMBCAA+FiEEEsKdz9s94XWwiuG96lQbuGeTCYsFAlwLCmACGwMFCQHhM4AFCwkIBwI GFQoJCAsCBBYCAwECHgECF4AACgkQ6lQbuGeTCYuQiQf9G2lkrkRdLjXehwCl+k5zBkn8MfUPi2It U2QDcBit/YyaZpNlSuh8h30gihp5Dlb9BnqBVKxooeIVKSKC1HFeG0AE28TvgCgEK8qP/LXaSzGvn udek2zxWtcsomqUftUWKvoDRi1AAWrPQmviNGZ4caMd4itKWf1sxzuH1qF5+me6eFaqhbIg4k+6C5 fk3oDBhg0zr0gLm5GRxK/lJtTNGpwsSwIJLtTI3zEdmNjW8bb/XKszf1ufy19maGXB3h6tA9TTHOF nktmDoWJCq9/OgQS0s2D7W7f/Pw3sKQghazRy9NqeMbRfHrLq27+Eb3Nt5PyiQuTE8JeAima7w98q uQ== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-2.fc42) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2025-10-15 at 17:08 +0200, Peter Zijlstra wrote: > On Sat, Oct 11, 2025 at 11:24:47AM -0700, Tim Chen wrote: > > During LLC load balancing, first check for tasks that prefer the > > destination LLC and balance them to it before others. > >=20 > > Mark source sched groups containing tasks preferring non local LLCs > > with the group_llc_balance flag. This ensures the load balancer later > > pulls or pushes these tasks toward their preferred LLCs. > >=20 > > Co-developed-by: Chen Yu > > Signed-off-by: Chen Yu > > Signed-off-by: Tim Chen > > --- >=20 > For me this patch is cut too fine; it only sets group_llc_balance but > then we don't see how it is used. Okay, will combine this patch with the following one. >=20 > > kernel/sched/fair.c | 43 +++++++++++++++++++++++++++++++++++++++++-- > > 1 file changed, 41 insertions(+), 2 deletions(-) > >=20 > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index cbd1e97bca4b..af7b578eaa06 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -9822,8 +9822,7 @@ static __maybe_unused enum llc_mig can_migrate_ll= c_task(int src_cpu, int dst_cpu > > else > > return mig_unrestricted; > > =20 > > - return can_migrate_llc(src_cpu, dst_cpu, > > - task_util(p), to_pref); > > + return can_migrate_llc(src_cpu, dst_cpu, task_util(p), to_pref); > > } > > =20 > > #else > > @@ -10394,6 +10393,7 @@ struct sg_lb_stats { > > enum group_type group_type; > > unsigned int group_asym_packing; /* Tasks should be moved to preferre= d CPU */ > > unsigned int group_smt_balance; /* Task on busy SMT be moved */ > > + unsigned int group_llc_balance; /* Tasks should be moved to preferre= d LLC */ > > unsigned long group_misfit_task_load; /* A CPU has a task too big for= its capacity */ > > #ifdef CONFIG_NUMA_BALANCING > > unsigned int nr_numa_running; > > @@ -10849,11 +10849,45 @@ static void record_sg_llc_stats(struct lb_env= *env, > > if (unlikely(READ_ONCE(sd_share->capacity) !=3D sgs->group_capacity)) > > WRITE_ONCE(sd_share->capacity, sgs->group_capacity); > > } > > + > > +/* > > + * Do LLC balance on sched group that contains LLC, and have tasks pre= ferring > > + * to run on LLC in idle dst_cpu. > > + */ > > +static inline bool llc_balance(struct lb_env *env, struct sg_lb_stats = *sgs, > > + struct sched_group *group) > > +{ > > + struct sched_domain *child =3D env->sd->child; > > + int llc; > > + > > + if (!sched_cache_enabled()) > > + return false; > > + > > + if (env->sd->flags & SD_SHARE_LLC) > > + return false; > > + > > + /* only care about task migration among LLCs */ > > + if (child && !(child->flags & SD_SHARE_LLC)) > > + return false; > > + > > + llc =3D llc_idx(env->dst_cpu); > > + if (sgs->nr_pref_llc[llc] > 0 && >=20 > Nit: s/> 0// would be the same, right? Sure. >=20 > > + can_migrate_llc(env->src_cpu, env->dst_cpu, 0, true) =3D=3D mig_l= lc) > > + return true; > > + > > + return false; > > +} > > #else > > static inline void record_sg_llc_stats(struct lb_env *env, struct sg_l= b_stats *sgs, > > struct sched_group *group) > > { > > } > > + > > +static inline bool llc_balance(struct lb_env *env, struct sg_lb_stats = *sgs, > > + struct sched_group *group) > > +{ > > + return false; > > +} > > #endif > > =20 > > /** > > @@ -10954,6 +10988,11 @@ static inline void update_sg_lb_stats(struct l= b_env *env, > > sgs->group_type =3D group_classify(env->sd->imbalance_pct, group, sgs= ); > > =20 > > record_sg_llc_stats(env, sgs, group); > > + > > + /* Check for tasks in this group can be moved to their preferred LLC = */ > > + if (!local_group && llc_balance(env, sgs, group)) > > + sgs->group_llc_balance =3D 1; >=20 > We now have 3 (or so) branches that start with: >=20 > if (!local_group && >=20 > perhaps collate that some? Sure. >=20 > > + > > /* Computing avg_load makes sense only when group is overloaded */ > > if (sgs->group_type =3D=3D group_overloaded) > > sgs->avg_load =3D (sgs->group_load * SCHED_CAPACITY_SCALE) / > > --=20 > > 2.32.0 > >=20