From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 CCABB3AFAE2; Wed, 30 Sep 2026 18:47:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790794022; cv=none; b=WpT0aiuWXS5RHwVYgrplG00w3yDUBHeDC9ad7F37b3S7wHEI+pU+J/3PQ5ptHyPXrDcPYbCziiaGnf/EPz59Nk0VR+sj9lVhWG8wHWzOdg1+/1tKudJ2ujPqW8Y90yK+N0mppPp7zM4zFmbfwlJVZ6BJffN5pshMr3Ynl/4bNco= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790794022; c=relaxed/simple; bh=O6+Y3jFqGm7ZjTWAccn7wOzWeF9e2iEKNKGopPecdU0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DAbc/t9SBH/89nUd4v3DoXuLLV1sdtsiW9225KTJI7iGpTH7JFILqKL/92voKfiJOGKzc8ks00oz++IA7mrj4SP/5wljiJlB5wsUzE4YhBa9mZkqQEADyYoBedEuUE9IXmigEg41Uy57qqoH9T2qU+yCcOznJIhTRhfSiRxfukw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=2NWU21Rp; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="2NWU21Rp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 236081F000FF; Wed, 30 Sep 2026 18:46:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790794020; bh=59jiseJLVKBU6G1Xt7ipE+1pvpTetrvqa5urfxSGVI4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=2NWU21RpZ8fR7cJUDVil/33h0nyNfHnpx/tth37BsFg8b+91KeRvB1XHYPQAcjmBK 6zan+JRFAif65LAUArP8R30OCrqhnV8UlNgbcw5x1yupqnXMch/UWOmhnIGCIJfGAj HYiUp1UbpCZQrymYi+Xes0t7eXomFEHT2197kbaY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Felix Abecassis , Andrea Righi , "Peter Zijlstra (Intel)" , Vincent Guittot , Sasha Levin Subject: [PATCH 6.6 0065/1193] sched/fair: Reject misfit pulls onto busy SMT siblings on asym-capacity Date: Wed, 30 Sep 2026 17:12:29 +0200 Message-ID: <20260930152435.715835157@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152434.301151190@linuxfoundation.org> References: <20260930152434.301151190@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andrea Righi [ Upstream commit bf6aa722198d3c06e4236e8c5a480f30a64e1513 ] When SD_ASYM_CPUCAPACITY load balancing considers pulling a misfit task, capacity_of(dst_cpu) can overstate available compute if the SMT sibling is busy: the core does not deliver its full nominal capacity. If SMT is active and dst_cpu is not on a fully idle core, skip this destination so we do not migrate a misfit expecting a capacity upgrade we cannot actually provide. Reported-by: Felix Abecassis Signed-off-by: Andrea Righi Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Vincent Guittot Link: https://patch.msgid.link/20260509180955.1840064-5-arighi@nvidia.com Signed-off-by: Sasha Levin --- kernel/sched/fair.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 43bc2f03e0c92..a1bdd45c62932 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8834,6 +8834,7 @@ struct lb_env { int dst_cpu; struct rq *dst_rq; + bool dst_core_idle; struct cpumask *dst_grpmask; int new_dst_cpu; @@ -10049,10 +10050,16 @@ static bool update_sd_pick_busiest(struct lb_env *env, * We can use max_capacity here as reduction in capacity on some * CPUs in the group should either be possible to resolve * internally or be covered by avg_load imbalance (eventually). + * + * When SMT is active, only pull a misfit to dst_cpu if it is on a + * fully idle core; otherwise the effective capacity of the core is + * reduced and we may not actually provide more capacity than the + * source. */ if ((env->sd->flags & SD_ASYM_CPUCAPACITY) && (sgs->group_type == group_misfit_task) && - (!capacity_greater(capacity_of(env->dst_cpu), sg->sgc->max_capacity) || + (!env->dst_core_idle || + !capacity_greater(capacity_of(env->dst_cpu), sg->sgc->max_capacity) || sds->local_stat.group_type != group_has_spare)) return false; @@ -10626,6 +10633,8 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd unsigned long sum_util = 0; int sg_status = 0; + env->dst_core_idle = !sched_smt_active() || is_core_idle(env->dst_cpu); + do { struct sg_lb_stats *sgs = &tmp_sgs; int local_group; -- 2.53.0