From patchwork Fri Dec 18 18:50:32 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jonathan Lemon X-Patchwork-Id: 11982783 X-Patchwork-Delegate: bpf@iogearbox.net 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=-13.7 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 32580C3526B for ; Fri, 18 Dec 2020 18:51:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E690423BA8 for ; Fri, 18 Dec 2020 18:51:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727233AbgLRSvQ convert rfc822-to-8bit (ORCPT ); Fri, 18 Dec 2020 13:51:16 -0500 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:55806 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725844AbgLRSvQ (ORCPT ); Fri, 18 Dec 2020 13:51:16 -0500 Received: from pps.filterd (m0044010.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 0BIIjkYM011775 for ; Fri, 18 Dec 2020 10:50:35 -0800 Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 35gwa89n2x-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Fri, 18 Dec 2020 10:50:35 -0800 Received: from intmgw005.03.ash8.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::f) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1979.3; Fri, 18 Dec 2020 10:50:33 -0800 Received: by devvm2494.atn0.facebook.com (Postfix, from userid 172786) id B671959F2C88; Fri, 18 Dec 2020 10:50:32 -0800 (PST) From: Jonathan Lemon To: , , , , CC: Subject: [PATCH 3/3 v4 bpf-next] bpf: optimize task iteration Date: Fri, 18 Dec 2020 10:50:32 -0800 Message-ID: <20201218185032.2464558-4-jonathan.lemon@gmail.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20201218185032.2464558-1-jonathan.lemon@gmail.com> References: <20201218185032.2464558-1-jonathan.lemon@gmail.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.343,18.0.737 definitions=2020-12-18_12:2020-12-18,2020-12-18 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 bulkscore=0 mlxlogscore=827 priorityscore=1501 phishscore=0 spamscore=0 lowpriorityscore=0 malwarescore=0 suspectscore=0 mlxscore=0 impostorscore=0 clxscore=1034 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012180127 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net From: Jonathan Lemon Only obtain the task reference count at the end of the RCU section instead of repeatedly obtaining/releasing it when iterating though a thread group. Jump to the correct branch when it is known that the task is NULL. Signed-off-by: Jonathan Lemon Acked-by: Andrii Nakryiko --- kernel/bpf/task_iter.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index dc4007f1843b..598a8d7da5bf 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -33,7 +33,7 @@ static struct task_struct *task_seq_get_next(struct pid_namespace *ns, pid = find_ge_pid(*tid, ns); if (pid) { *tid = pid_nr_ns(pid, ns); - task = get_pid_task(pid, PIDTYPE_PID); + task = pid_task(pid, PIDTYPE_PID); if (!task) { ++*tid; goto retry; @@ -44,6 +44,7 @@ static struct task_struct *task_seq_get_next(struct pid_namespace *ns, ++*tid; goto retry; } + get_task_struct(task); } rcu_read_unlock(); @@ -148,12 +149,12 @@ task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info) * it held a reference to the task/files_struct/file. * Otherwise, it does not hold any reference. */ -again: if (info->task) { curr_task = info->task; curr_files = info->files; curr_fd = info->fd; } else { +again: curr_task = task_seq_get_next(ns, &curr_tid, true); if (!curr_task) { info->task = NULL;