From patchwork Wed Jan 13 21:33:20 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stanislav Fomichev X-Patchwork-Id: 12018365 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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 2FCE6C433E9 for ; Thu, 14 Jan 2021 02:14:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DC5852242A for ; Thu, 14 Jan 2021 02:14:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726534AbhANCN7 (ORCPT ); Wed, 13 Jan 2021 21:13:59 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44382 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729160AbhAMVfQ (ORCPT ); Wed, 13 Jan 2021 16:35:16 -0500 Received: from mail-qv1-xf49.google.com (mail-qv1-xf49.google.com [IPv6:2607:f8b0:4864:20::f49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 29414C0617A3 for ; Wed, 13 Jan 2021 13:33:28 -0800 (PST) Received: by mail-qv1-xf49.google.com with SMTP id u8so2689521qvm.5 for ; Wed, 13 Jan 2021 13:33:28 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=eVYXXRCuyKFusFzDUDSL6GRAD9v9jG1oOwxOSa05otY=; b=tuv5zjtU+6iaPolZxTZVMr8uzUzirJkKX2qpjZkCQdxVCx/L2gm1Wyd+F1RwKDkoD9 c64O6M7HAffBiGvzlkyk0INbhoFCPY4CrQkw9SOpJpUJ9RZtVxA6D+flRepuFsjJ28uy Ve2y1pSYDfOqJwAjrGjz8a6E1biO07Dd9yQ9EU5SV+1BImmo0oGiHo9JIjeuyZnxDB/J FqjA7Agc0qRLy1Uz2w1sKm/CcflDLVyHAOl8FDubQAujdWccI1xBQ94IwKRFnKdDdqdn VTCqVnly7Rf9OCs3uj38lZc69eMKpyXbIuwwEcKsVg8NNSFanKBoULPIOAxMEnmpvxOy uHJw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=eVYXXRCuyKFusFzDUDSL6GRAD9v9jG1oOwxOSa05otY=; b=Vfr/D6jhaUqFqTEcN6LzjAzpVdEKWmZ51Ddi/Wvv95/vVF1BQ8HKi1n64gXkrir3RK df2RFqQThs1jQbvaarfKKj7J5Lj7C96jlIMUD+DAod/86fg5FQxVli5+fSFxbcH3RYaF UPl8Z8mqdr73YdyMcVUjH5fxvX7D7+rUYo4IJ61OfXNDVWrRSKLYDaGp5ZHAWXvmalsg lQB4wKiD10dtDbLj2PMU1k64zww/BsN9LQsCdDh4Hkb5dOJ8nKcmVS85svURInK3FqlY z1roNlMOzU5ohPPuwopoEKqlHzDO1nhsZ9+LZFMcuwvfRkWuHpqDB8Tfx2wqVHBrIUyj cyDg== X-Gm-Message-State: AOAM533QZrmzsLvxmk5Cf6ejrQw3OtbonRH4TMp6XYh1SQ1tgqksjGRq 5jKIiPs1ViUQio0vkkzXDKPOk7Q= X-Google-Smtp-Source: ABdhPJxR/W0EyWMMw5RwPbb8gyNATDZKmo+3V0LUQ1bDMIZmqfSSmXzluxSx+wHjxEK3GJ2cXtSYCYM= Sender: "sdf via sendgmr" X-Received: from sdf2.svl.corp.google.com ([2620:15c:2c4:1:7220:84ff:fe09:7732]) (user=sdf job=sendgmr) by 2002:a05:6214:14ae:: with SMTP id bo14mr4163889qvb.16.1610573607347; Wed, 13 Jan 2021 13:33:27 -0800 (PST) Date: Wed, 13 Jan 2021 13:33:20 -0800 In-Reply-To: <20210113213321.2832906-1-sdf@google.com> Message-Id: <20210113213321.2832906-3-sdf@google.com> Mime-Version: 1.0 References: <20210113213321.2832906-1-sdf@google.com> X-Mailer: git-send-email 2.30.0.284.gd98b1dd5eaa7-goog Subject: [PATCH bpf-next v8 2/3] bpf: try to avoid kzalloc in cgroup/{s,g}etsockopt From: Stanislav Fomichev To: netdev@vger.kernel.org, bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, Stanislav Fomichev , Martin KaFai Lau , Song Liu Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net When we attach a bpf program to cgroup/getsockopt any other getsockopt() syscall starts incurring kzalloc/kfree cost. Let add a small buffer on the stack and use it for small (majority) {s,g}etsockopt values. The buffer is small enough to fit into the cache line and cover the majority of simple options (most of them are 4 byte ints). It seems natural to do the same for setsockopt, but it's a bit more involved when the BPF program modifies the data (where we have to kmalloc). The assumption is that for the majority of setsockopt calls (which are doing pure BPF options or apply policy) this will bring some benefit as well. Without this patch (we remove about 1% __kmalloc): 3.38% 0.07% tcp_mmap [kernel.kallsyms] [k] __cgroup_bpf_run_filter_getsockopt | --3.30%--__cgroup_bpf_run_filter_getsockopt | --0.81%--__kmalloc Signed-off-by: Stanislav Fomichev Cc: Martin KaFai Lau Cc: Song Liu Acked-by: Martin KaFai Lau --- include/linux/filter.h | 5 ++++ kernel/bpf/cgroup.c | 52 ++++++++++++++++++++++++++++++++++++------ 2 files changed, 50 insertions(+), 7 deletions(-) diff --git a/include/linux/filter.h b/include/linux/filter.h index 5edf2b660881..6dbe85973cfb 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -1281,6 +1281,11 @@ struct bpf_sysctl_kern { u64 tmp_reg; }; +#define BPF_SOCKOPT_KERN_BUF_SIZE 32 +struct bpf_sockopt_buf { + u8 data[BPF_SOCKOPT_KERN_BUF_SIZE]; +}; + struct bpf_sockopt_kern { struct sock *sk; u8 *optval; diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index 416e7738981b..ba8a1199d0ba 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -1298,7 +1298,8 @@ static bool __cgroup_bpf_prog_array_is_empty(struct cgroup *cgrp, return empty; } -static int sockopt_alloc_buf(struct bpf_sockopt_kern *ctx, int max_optlen) +static int sockopt_alloc_buf(struct bpf_sockopt_kern *ctx, int max_optlen, + struct bpf_sockopt_buf *buf) { if (unlikely(max_optlen < 0)) return -EINVAL; @@ -1310,6 +1311,15 @@ static int sockopt_alloc_buf(struct bpf_sockopt_kern *ctx, int max_optlen) max_optlen = PAGE_SIZE; } + if (max_optlen <= sizeof(buf->data)) { + /* When the optval fits into BPF_SOCKOPT_KERN_BUF_SIZE + * bytes avoid the cost of kzalloc. + */ + ctx->optval = buf->data; + ctx->optval_end = ctx->optval + max_optlen; + return max_optlen; + } + ctx->optval = kzalloc(max_optlen, GFP_USER); if (!ctx->optval) return -ENOMEM; @@ -1319,16 +1329,26 @@ static int sockopt_alloc_buf(struct bpf_sockopt_kern *ctx, int max_optlen) return max_optlen; } -static void sockopt_free_buf(struct bpf_sockopt_kern *ctx) +static void sockopt_free_buf(struct bpf_sockopt_kern *ctx, + struct bpf_sockopt_buf *buf) { + if (ctx->optval == buf->data) + return; kfree(ctx->optval); } +static bool sockopt_buf_allocated(struct bpf_sockopt_kern *ctx, + struct bpf_sockopt_buf *buf) +{ + return ctx->optval != buf->data; +} + int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, int *optname, char __user *optval, int *optlen, char **kernel_optval) { struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data); + struct bpf_sockopt_buf buf = {}; struct bpf_sockopt_kern ctx = { .sk = sk, .level = *level, @@ -1350,7 +1370,7 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, */ max_optlen = max_t(int, 16, *optlen); - max_optlen = sockopt_alloc_buf(&ctx, max_optlen); + max_optlen = sockopt_alloc_buf(&ctx, max_optlen, &buf); if (max_optlen < 0) return max_optlen; @@ -1390,14 +1410,31 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, */ if (ctx.optlen != 0) { *optlen = ctx.optlen; - *kernel_optval = ctx.optval; + /* We've used bpf_sockopt_kern->buf as an intermediary + * storage, but the BPF program indicates that we need + * to pass this data to the kernel setsockopt handler. + * No way to export on-stack buf, have to allocate a + * new buffer. + */ + if (!sockopt_buf_allocated(&ctx, &buf)) { + void *p = kmalloc(ctx.optlen, GFP_USER); + + if (!p) { + ret = -ENOMEM; + goto out; + } + memcpy(p, ctx.optval, ctx.optlen); + *kernel_optval = p; + } else { + *kernel_optval = ctx.optval; + } /* export and don't free sockopt buf */ return 0; } } out: - sockopt_free_buf(&ctx); + sockopt_free_buf(&ctx, &buf); return ret; } @@ -1407,6 +1444,7 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level, int retval) { struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data); + struct bpf_sockopt_buf buf = {}; struct bpf_sockopt_kern ctx = { .sk = sk, .level = level, @@ -1425,7 +1463,7 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level, ctx.optlen = max_optlen; - max_optlen = sockopt_alloc_buf(&ctx, max_optlen); + max_optlen = sockopt_alloc_buf(&ctx, max_optlen, &buf); if (max_optlen < 0) return max_optlen; @@ -1483,7 +1521,7 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level, ret = ctx.retval; out: - sockopt_free_buf(&ctx); + sockopt_free_buf(&ctx, &buf); return ret; }