From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) (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 B7FAF11CA0 for ; Sun, 15 Sep 2024 07:21:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726384884; cv=none; b=hfOYfXKqvCKzMUOUDBcym4heiGDSj+5mP+hJy6FM14HWJfCcbJDf+pESdDLGQVU1arUafHG3ryVJyJxOAhUkqLo4h//GFUMAA+JRsJIhcimdwVV3emGozJjZV22qMhJ4uiEFadcXKiA1c6MKO+r8PIDeF9cem4a5LMH7D7IgIME= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726384884; c=relaxed/simple; bh=I8I7UJsfsjG1jFT8o5/Or+dsqXlOfwsRo//uwzCiOi4=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=cdM78CYNxjrpYer77TfDrE/+Hern0fLXzNWEO8eAO14hVUvbasslqmnMUO/WNhFOBp/jae2C8UJW2sFmr6+PpBc/bOcUwmSoowuehNPcnS/YCcGlpVFj7Jr5AbtVKN91lcquwOwqPPXv6pK0DhHM4G6rLwK3MphcfSTgaipg25c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.88.194]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4X5ztf2CM3zfbnx; Sun, 15 Sep 2024 15:19:06 +0800 (CST) Received: from kwepemd100013.china.huawei.com (unknown [7.221.188.163]) by mail.maildlp.com (Postfix) with ESMTPS id A6D5814035F; Sun, 15 Sep 2024 15:21:18 +0800 (CST) Received: from huawei.com (10.67.174.121) by kwepemd100013.china.huawei.com (7.221.188.163) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1258.34; Sun, 15 Sep 2024 15:21:18 +0800 From: Chen Ridong To: , , , , , , , CC: Subject: [PATHC v3 -next 1/3] cgroup/freezer: Reduce redundant traversal for cgroup_freeze Date: Sun, 15 Sep 2024 07:13:05 +0000 Message-ID: <20240915071307.1976026-2-chenridong@huawei.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240915071307.1976026-1-chenridong@huawei.com> References: <20240915071307.1976026-1-chenridong@huawei.com> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemd100013.china.huawei.com (7.221.188.163) Whether a cgroup is frozen is determined solely by whether it is set to to be frozen and whether its parent is frozen. Currently, when is cgroup is frozen or unfrozen, it iterates through the entire subtree to freeze or unfreeze its descentdants. However, this is unesessary for a cgroup that does not change its effective frozen status. This path aims to skip the subtree if its parent does not have a change in effective freeze. For an example, subtree like, a-b-c-d-e-f-g, when a is frozen, the entire tree is frozen. If we freeze b and c again, it is unesessary to iterate d, e, f and g. So does that If we unfreeze b/c. Signed-off-by: Chen Ridong --- include/linux/cgroup-defs.h | 2 +- kernel/cgroup/freezer.c | 30 ++++++++++++++---------------- 2 files changed, 15 insertions(+), 17 deletions(-) diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 47ae4c4d924c..dd1ecab99eeb 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -397,7 +397,7 @@ struct cgroup_freezer_state { bool freeze; /* Should the cgroup actually be frozen? */ - int e_freeze; + bool e_freeze; /* Fields below are protected by css_set_lock */ diff --git a/kernel/cgroup/freezer.c b/kernel/cgroup/freezer.c index 617861a54793..188d5f2aeb5a 100644 --- a/kernel/cgroup/freezer.c +++ b/kernel/cgroup/freezer.c @@ -260,8 +260,10 @@ void cgroup_freezer_migrate_task(struct task_struct *task, void cgroup_freeze(struct cgroup *cgrp, bool freeze) { struct cgroup_subsys_state *css; + struct cgroup *parent; struct cgroup *dsct; bool applied = false; + bool old_e; lockdep_assert_held(&cgroup_mutex); @@ -282,22 +284,18 @@ void cgroup_freeze(struct cgroup *cgrp, bool freeze) if (cgroup_is_dead(dsct)) continue; - if (freeze) { - dsct->freezer.e_freeze++; - /* - * Already frozen because of ancestor's settings? - */ - if (dsct->freezer.e_freeze > 1) - continue; - } else { - dsct->freezer.e_freeze--; - /* - * Still frozen because of ancestor's settings? - */ - if (dsct->freezer.e_freeze > 0) - continue; - - WARN_ON_ONCE(dsct->freezer.e_freeze < 0); + /* + * e_freeze is affected by parent's e_freeze and dst's freeze. + * If old e_freeze eq new e_freeze, no change, its children + * will not be affected. So do nothing and skip the subtree + */ + old_e = dsct->freezer.e_freeze; + parent = cgroup_parent(dsct); + dsct->freezer.e_freeze = (dsct->freezer.freeze || + parent->freezer.e_freeze); + if (dsct->freezer.e_freeze == old_e) { + css = css_rightmost_descendant(css); + continue; } /* -- 2.34.1