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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 A3187C10DCE for ; Tue, 24 Mar 2020 23:46:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 758322072E for ; Tue, 24 Mar 2020 23:46:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="akXeOs+e" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727054AbgCXXqH (ORCPT ); Tue, 24 Mar 2020 19:46:07 -0400 Received: from mail-qt1-f194.google.com ([209.85.160.194]:35695 "EHLO mail-qt1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726212AbgCXXqH (ORCPT ); Tue, 24 Mar 2020 19:46:07 -0400 Received: by mail-qt1-f194.google.com with SMTP id e14so653248qts.2; Tue, 24 Mar 2020 16:46:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=12i54rUV2CjnkiSHxgDtqYU9HJzD0mdT3615spsxFH8=; b=akXeOs+eztP6yWqwQKA1sCESeZjTy9HsVIQYasVqQf0g5d0KlmXD4Gy13x6nOa7C1S MAPFxJ6f3O3RJbgnt4dlFu7aUUnxt8w/F4Dy8KzcB4UfgmxCEhHSBclL/I4Xb4xuAMti AKlhopGzGDpBfvBicGW04W3LqBgiSawHATMJHJBGWU57oBI7oCabgHbtu0y/FcEyXZpK 6qqLUHUpYBaHNenCEvrXfsu6IKDhwKcVNcrgCq8vRSLCG3LCAJoSMdt/zIBbZM2LIyZ+ b8oFpyXdWhd1co1GumP+kAQi4H5uQ5/mVkzj2bsd+rqdnVLbwA8/Ss3yqaevNICoMH5q mpjg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=12i54rUV2CjnkiSHxgDtqYU9HJzD0mdT3615spsxFH8=; b=nCBXq0/SurpSUWmWnFY30s1Auc8rOHj17kKhSEVq3i+w1xUBZeIv/zTS/1ljCMCVDS UVY7jFTB4Fum902UzIunKjRG0Svvb5r6112rkutd9xuvl48gh36T8kP8mqoXndfbDKaY LLehgWZ/UaiURkWIJPnE6vRl5SNZdm9jro6MYqYVCy6W4J2+k7+zXvfWbgUS56R2G7dW QzT0g/CyOGZpG44lzeFcbpCTT7GUZIenaN6TkeqF75BkGkmDqrVc8UsXWfF3cmhVUdqj 4w5utWdnnQXWs+LRd6Ptx4FWqqEZ72Nz6rHAtp5Ze73/DWFX7UW7tHyOJwlOrrDyRigU zFyQ== X-Gm-Message-State: ANhLgQ0pyG8OHAyAF6eoVKdspCyQoDExZj5iaxLe0ECo7OeMslVG3scw dL4SBi5dmWsfqmvQaWqx0F+dfR0XDCbNnSdQhOw= X-Google-Smtp-Source: ADFU+vsiBX7zxNz/Bx//POeFEBNxoJxycjjU1/vJCQ4IQvcyM2EFkezPLMDdBuohXJIuEutebn9T5lN+WQhcjkDtQ/0= X-Received: by 2002:ac8:7cb0:: with SMTP id z16mr404024qtv.59.1585093565473; Tue, 24 Mar 2020 16:46:05 -0700 (PDT) MIME-Version: 1.0 References: <20200324233120.66314-1-sdf@google.com> In-Reply-To: <20200324233120.66314-1-sdf@google.com> From: Andrii Nakryiko Date: Tue, 24 Mar 2020 16:45:54 -0700 Message-ID: Subject: Re: [PATCH bpf-next] libbpf: don't allocate 16M for log buffer by default To: Stanislav Fomichev Cc: Networking , bpf , "David S. Miller" , Alexei Starovoitov , Daniel Borkmann Content-Type: text/plain; charset="UTF-8" Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Mar 24, 2020 at 4:31 PM Stanislav Fomichev wrote: > > For each prog/btf load we allocate and free 16 megs of verifier buffer. > On production systems it doesn't really make sense because the > programs/btf have gone through extensive testing and (mostly) guaranteed > to successfully load. > > Let's switch to a much smaller buffer by default (128 bytes, sys_bpf > doesn't accept smaller log buffer) and resize it if the kernel returns > ENOSPC. On the first ENOSPC error we resize the buffer to BPF_LOG_BUF_SIZE > and then, on each subsequent ENOSPC, we keep doubling the buffer. > > Signed-off-by: Stanislav Fomichev > --- > tools/lib/bpf/btf.c | 10 +++++++++- > tools/lib/bpf/libbpf.c | 10 ++++++++-- > tools/lib/bpf/libbpf_internal.h | 2 ++ > 3 files changed, 19 insertions(+), 3 deletions(-) > > diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c > index 3d1c25fc97ae..53c7efc3b347 100644 > --- a/tools/lib/bpf/btf.c > +++ b/tools/lib/bpf/btf.c > @@ -657,13 +657,14 @@ int btf__finalize_data(struct bpf_object *obj, struct btf *btf) > > int btf__load(struct btf *btf) > { > - __u32 log_buf_size = BPF_LOG_BUF_SIZE; > + __u32 log_buf_size = BPF_MIN_LOG_BUF_SIZE; > char *log_buf = NULL; > int err = 0; > > if (btf->fd >= 0) > return -EEXIST; > > +retry_load: > log_buf = malloc(log_buf_size); > if (!log_buf) > return -ENOMEM; I'd argue that on first try we shouldn't allocate log_buf at all, then start allocating it using reasonable starting size (see below). > @@ -673,6 +674,13 @@ int btf__load(struct btf *btf) > btf->fd = bpf_load_btf(btf->data, btf->data_size, > log_buf, log_buf_size, false); > if (btf->fd < 0) { > + if (errno == ENOSPC) { > + log_buf_size = max((__u32)BPF_LOG_BUF_SIZE, > + log_buf_size << 1); > + free(log_buf); > + goto retry_load; > + } > + > err = -errno; > pr_warn("Error loading BTF: %s(%d)\n", strerror(errno), errno); > if (*log_buf) > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 085e41f9b68e..793c81b35ccc 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -4855,7 +4855,7 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt, > { > struct bpf_load_program_attr load_attr; > char *cp, errmsg[STRERR_BUFSIZE]; > - int log_buf_size = BPF_LOG_BUF_SIZE; > + size_t log_buf_size = BPF_MIN_LOG_BUF_SIZE; > char *log_buf; > int btf_fd, ret; > > @@ -4911,7 +4911,13 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt, > } > > if (errno == ENOSPC) { same, doing if (!log_buf || errno == ENOSPC) should handle this without any other major changes? > - log_buf_size <<= 1; > + if (errno == ENOSPC) { > + log_buf_size = max((size_t)BPF_LOG_BUF_SIZE, > + log_buf_size << 1); > + free(log_buf); > + goto retry_load; > + } > + > free(log_buf); > goto retry_load; > } > diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h > index 8c3afbd97747..2720f3366798 100644 > --- a/tools/lib/bpf/libbpf_internal.h > +++ b/tools/lib/bpf/libbpf_internal.h > @@ -23,6 +23,8 @@ > #define BTF_PARAM_ENC(name, type) (name), (type) > #define BTF_VAR_SECINFO_ENC(type, offset, size) (type), (offset), (size) > > +#define BPF_MIN_LOG_BUF_SIZE 128 This seems way too low, if there is some error it almost certainly will be too short, probably for few iterations, just causing waste. Let's make it something a bit more reasonable, like 32KB or something? > + > #ifndef min > # define min(x, y) ((x) < (y) ? (x) : (y)) > #endif > -- > 2.25.1.696.g5e7596f4ac-goog >