From patchwork Wed Sep 2 00:26:08 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yonghong Song X-Patchwork-Id: 261661 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 35D94C433E6 for ; Wed, 2 Sep 2020 00:26:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F3039206EF for ; Wed, 2 Sep 2020 00:26:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="COtkyIAN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726226AbgIBA0P (ORCPT ); Tue, 1 Sep 2020 20:26:15 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:63242 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726107AbgIBA0O (ORCPT ); Tue, 1 Sep 2020 20:26:14 -0400 Received: from pps.filterd (m0109334.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 0820NDKc001586 for ; Tue, 1 Sep 2020 17:26:14 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=mq0ef9jOqeU3dqaAcGpJaqz/OttVubZ/GMgdk24nemU=; b=COtkyIANcfXU596rWyesohDmov+4XGIES5Fkp9OVWiQNgXANvT0VBctOaXepsA6/38Qj 2KU5DdhwL14Y1cq9PzBE3N6lHyFGZDIIFOSBKRqHjRjeLLwuW0OFK4YHi+pZ4bnoLteG vmxzd4is0L5jvfWlmbp5u90TjUCUl+ythoo= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 3386ukp6ua-2 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Tue, 01 Sep 2020 17:26:14 -0700 Received: from intmgw002.08.frc2.facebook.com (2620:10d:c085:208::f) by mail.thefacebook.com (2620:10d:c085:11d::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Tue, 1 Sep 2020 17:26:13 -0700 Received: by devbig003.ftw2.facebook.com (Postfix, from userid 128203) id 687A03705183; Tue, 1 Sep 2020 17:26:08 -0700 (PDT) From: Yonghong Song To: , CC: Alexei Starovoitov , Daniel Borkmann , , Andrii Nakryiko , Josef Bacik Subject: [PATCH bpf-next v3 1/2] bpf: avoid iterating duplicated files for task_file iterator Date: Tue, 1 Sep 2020 17:26:08 -0700 Message-ID: <20200902002608.994712-1-yhs@fb.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200902002608.994598-1-yhs@fb.com> References: <20200902002608.994598-1-yhs@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687 definitions=2020-09-01_10:2020-09-01,2020-09-01 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 lowpriorityscore=0 adultscore=0 mlxscore=0 mlxlogscore=999 suspectscore=8 clxscore=1015 impostorscore=0 malwarescore=0 bulkscore=0 spamscore=0 phishscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009020002 X-FB-Internal: deliver Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Currently, task_file iterator iterates all files from all tasks. This may potentially visit a lot of duplicated files if there are many tasks sharing the same files, e.g., typical pthreads where these pthreads and the main thread are sharing the same files. This patch changed task_file iterator to skip a particular task if that task shares the same files as its group_leader (the task having the same tgid and also task->tgid == task->pid). This will preserve the same result, visiting all files from all tasks, and will reduce runtime cost significantl, e.g., if there are a lot of pthreads and the process has a lot of open files. Suggested-by: Andrii Nakryiko Reviewed-by: Josef Bacik Signed-off-by: Yonghong Song --- kernel/bpf/task_iter.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index 99af4cea1102..5b6af30bfbcd 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -22,7 +22,8 @@ struct bpf_iter_seq_task_info { }; static struct task_struct *task_seq_get_next(struct pid_namespace *ns, - u32 *tid) + u32 *tid, + bool skip_if_dup_files) { struct task_struct *task = NULL; struct pid *pid; @@ -36,6 +37,12 @@ static struct task_struct *task_seq_get_next(struct pid_namespace *ns, if (!task) { ++*tid; goto retry; + } else if (skip_if_dup_files && task->tgid != task->pid && + task->files == task->group_leader->files) { + put_task_struct(task); + task = NULL; + ++*tid; + goto retry; } } rcu_read_unlock(); @@ -48,7 +55,7 @@ static void *task_seq_start(struct seq_file *seq, loff_t *pos) struct bpf_iter_seq_task_info *info = seq->private; struct task_struct *task; - task = task_seq_get_next(info->common.ns, &info->tid); + task = task_seq_get_next(info->common.ns, &info->tid, false); if (!task) return NULL; @@ -65,7 +72,7 @@ static void *task_seq_next(struct seq_file *seq, void *v, loff_t *pos) ++*pos; ++info->tid; put_task_struct((struct task_struct *)v); - task = task_seq_get_next(info->common.ns, &info->tid); + task = task_seq_get_next(info->common.ns, &info->tid, false); if (!task) return NULL; @@ -148,7 +155,7 @@ task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info, curr_files = *fstruct; curr_fd = info->fd; } else { - curr_task = task_seq_get_next(ns, &curr_tid); + curr_task = task_seq_get_next(ns, &curr_tid, true); if (!curr_task) return NULL;