From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 97F10C43334 for ; Wed, 29 Jun 2022 16:19:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231613AbiF2QTM (ORCPT ); Wed, 29 Jun 2022 12:19:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33966 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229649AbiF2QTL (ORCPT ); Wed, 29 Jun 2022 12:19:11 -0400 Received: from mail-pj1-x1049.google.com (mail-pj1-x1049.google.com [IPv6:2607:f8b0:4864:20::1049]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0BE23220F4 for ; Wed, 29 Jun 2022 09:19:11 -0700 (PDT) Received: by mail-pj1-x1049.google.com with SMTP id f8-20020a17090ac28800b001ed312c6fe1so5791267pjt.8 for ; Wed, 29 Jun 2022 09:19:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=7SL+gVI/1fryiXm08kyzMRVdUsXymda8l5P6QPOWawE=; b=H3XcadEg4vciLzRz4FYeNoHZOSwjncFglokoX9llcnmukYNDhHjrIB04MiFmu7CxYz w7DQanNzY6SkkhfvrLFmJQZYQavVHw870ZBd7aTe3byVVv09skv3qtPgqKOlnvhVZ02/ TvgePho6cduPYSwAp4/faB2iAr7nFu9MxuwzFCF7s/F1Pntxw1e//yResZoiJTrAyya2 J+zoNVcXW1sDERfnfj+qx0gRkaO147nKB49rFLGqIgC6IpB+hRcf24Ss6iaWVdNXKHxQ 7G+SHkU4Ud/2CPS5tXyFHEiYjKre9PmvEVMCrNRZboQ9mcUZzPP2mkIsfURel/Xf27Dj FVxw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=7SL+gVI/1fryiXm08kyzMRVdUsXymda8l5P6QPOWawE=; b=bessWFWexDY5Ed+mt4W3BvGE12JsVNobT7NhnlKSHwf3ajoWDI73/2OPwLIdbohx6q XpSNdeeqqtQ9OMS+X983dRzudsnuSbvx7a+/fJOXMBEnmdsuIUk7UpaTpY8XGKnAW5or ATGIr5uvk8S3oGonL1BB6Z4S1BJJdO2p8p9tHGkN6cOokthAYiVv3lSbKT0ka52TMQKH mUprM/SWVKUXKieRDtp05x70FCC29TVepYem0pkYVJPbW3kVZsnhiVywvLPdzttVf/lb SRKVGFGFhJaz3WU8apxxitFB9idJneExFQfIB6EraG5NgrhuXxQh7GXJdyKYngUBWElB 0m8Q== X-Gm-Message-State: AJIora9iwFbx9HmsosQfvtcWtrN7NxJJssT5sXrx7uBZPcnAVpWd79ra HC1lUd4LJ7n3I/tDG3NGUPtvGDk= X-Google-Smtp-Source: AGRyM1u1W1f8DXAze5wNrV2deRxfeHXDBJqxZSrE/Dzb/pWBlmtNMjFV7O+3nTvmyiPBF4d8LWK4ilY= X-Received: from sdf.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5935]) (user=sdf job=sendgmr) by 2002:a17:90a:d904:b0:1ec:730c:bcac with SMTP id c4-20020a17090ad90400b001ec730cbcacmr6665641pjv.93.1656519550556; Wed, 29 Jun 2022 09:19:10 -0700 (PDT) Date: Wed, 29 Jun 2022 09:19:08 -0700 In-Reply-To: <20220629111351.47699-1-quentin@isovalent.com> Message-Id: Mime-Version: 1.0 References: <20220629111351.47699-1-quentin@isovalent.com> Subject: Re: [PATCH bpf-next v2] bpftool: Probe for memcg-based accounting before bumping rlimit From: sdf@google.com To: Quentin Monnet Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , bpf@vger.kernel.org, netdev@vger.kernel.org, Yafang Shao Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 06/29, Quentin Monnet wrote: > Bpftool used to bump the memlock rlimit to make sure to be able to load > BPF objects. After the kernel has switched to memcg-based memory > accounting [0] in 5.11, bpftool has relied on libbpf to probe the system > for memcg-based accounting support and for raising the rlimit if > necessary [1]. But this was later reverted, because the probe would > sometimes fail, resulting in bpftool not being able to load all required > objects [2]. > Here we add a more efficient probe, in bpftool itself. We first lower > the rlimit to 0, then we attempt to load a BPF object (and finally reset > the rlimit): if the load succeeds, then memcg-based memory accounting is > supported. > This approach was earlier proposed for the probe in libbpf itself [3], > but given that the library may be used in multithreaded applications, > the probe could have undesirable consequences if one thread attempts to > lock kernel memory while memlock rlimit is at 0. Since bpftool is > single-threaded and the rlimit is process-based, this is fine to do in > bpftool itself. > This probe was inspired by the similar one from the cilium/ebpf Go > library [4]. > v2: > - Simply use sizeof(attr) instead of hardcoding a size via > offsetofend(). > - Set r0 = 0 before returning in sample program. > [0] commit 97306be45fbe ("Merge branch 'switch to memcg-based memory > accounting'") > [1] commit a777e18f1bcd ("bpftool: Use libbpf 1.0 API mode instead of > RLIMIT_MEMLOCK") > [2] commit 6b4384ff1088 ("Revert "bpftool: Use libbpf 1.0 API mode > instead of RLIMIT_MEMLOCK"") > [3] > https://lore.kernel.org/bpf/20220609143614.97837-1-quentin@isovalent.com/t/#u > [4] https://github.com/cilium/ebpf/blob/v0.9.0/rlimit/rlimit.go#L39 > Cc: Stanislav Fomichev Reviewed-by: Stanislav Fomichev