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 46DC9C6FA8E for ; Fri, 24 Feb 2023 22:32:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229492AbjBXWcW (ORCPT ); Fri, 24 Feb 2023 17:32:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39224 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229723AbjBXWcU (ORCPT ); Fri, 24 Feb 2023 17:32:20 -0500 Received: from mail-pl1-x64a.google.com (mail-pl1-x64a.google.com [IPv6:2607:f8b0:4864:20::64a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EEDFE6F83F for ; Fri, 24 Feb 2023 14:32:18 -0800 (PST) Received: by mail-pl1-x64a.google.com with SMTP id l10-20020a17090270ca00b0019caa6e6bd1so378778plt.2 for ; Fri, 24 Feb 2023 14:32:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=REuCFk2S5TTI6JICtAIq6KFXHW44RnkCRjGEJPU2oHw=; b=bDeznkgY1EtV198z1G4NUw/XuUr+8S1QFFkPxKIK45Uh3TJ72Zi2A/niXfmgXzLeyQ reeTR+6ShHnfO3c/mp1BMr6Mjk6DCHjUKX8UKYSYaxp4Bn3GN84mCbsSwIYCKxzYX3bg gSrXuYWkjGOLLWJ6ekFExSJJCRs7w7FPhj8IbMgYeAJC1PBGaVaipR4rVCzdCavyWHON 0WwXfYsbwnKva8w3t5HIDNWK3QEIe+Z0K8LXU8zVPOfU7zoHPhiqMUeGYd4MQPnhRAd9 zgWr+v4cvM6JWKIbdV6DPMablLzawNYof4uF0nyxCC01R5bl9EG4zAfZBXkGjtwOimnw Vrxw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=REuCFk2S5TTI6JICtAIq6KFXHW44RnkCRjGEJPU2oHw=; b=M1iafxlb5MBg35hZHCGcX28mDgzbURmhy9VePsk3f02HS7r6+tWFz52tUA3XiaB7XX If43uD7dRWMLC5cHpW7PSexwNpewk0/3pfBqj9AtNwlOqJfb0oxSa7ocmFOz59m85FQQ dhCYlb2YUKwJXGjuWkc7kXY3XUfU70ub4uQ6FZhv0LuSZGz6/NMUC5XQJfW3b+0NLAR6 Gb/TUmnxRL/DSIVqCr/FBDZm33EYv1rZqqIvhuG+ec0ORgjt0ZUH3vmqS9bQNm3TGdja 5F8aEFbZuw66nDPvNHNQWjKeGI0ciJoLmca8WZtQJYgIdjNre+dwPDzUPShdy7L0qqPd lD4Q== X-Gm-Message-State: AO0yUKXDLAWEYUIcRecrujSy4OU4XihkngAOOjNg7e5gM93CatCT4tR4 sL+wcPuJh2JoumoCs5PVTJN6Exs= X-Google-Smtp-Source: AK7set/OT7XvbzEFuiRrehpIdqvEirWbSMMxi9Gcysjo/K8ggUEpu+o2Tx99tTiEaKl4H91d6wxDwGA= X-Received: from sdf.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5935]) (user=sdf job=sendgmr) by 2002:a05:6a02:241:b0:502:f8a4:86db with SMTP id bi1-20020a056a02024100b00502f8a486dbmr509454pgb.1.1677277938278; Fri, 24 Feb 2023 14:32:18 -0800 (PST) Date: Fri, 24 Feb 2023 14:32:16 -0800 In-Reply-To: <20230223215311.926899-2-aditi.ghag@isovalent.com> Mime-Version: 1.0 References: <20230223215311.926899-1-aditi.ghag@isovalent.com> <20230223215311.926899-2-aditi.ghag@isovalent.com> Message-ID: Subject: Re: [PATCH v2 bpf-next 1/3] bpf: Implement batching in UDP iterator From: Stanislav Fomichev To: Aditi Ghag Cc: bpf@vger.kernel.org, kafai@fb.com, edumazet@google.com, Martin KaFai Lau Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 02/23, Aditi Ghag wrote: > Batch UDP sockets from BPF iterator that allows for overlapping locking > semantics in BPF/kernel helpers executed in BPF programs. This > facilitates > BPF socket destroy kfunc (introduced by follow-up patches) to execute from > BPF iterator programs. > Previously, BPF iterators acquired the sock lock and sockets hash table > bucket lock while executing BPF programs. This prevented BPF helpers that > again acquire these locks to be executed from BPF iterators. With the > batching approach, we acquire a bucket lock, batch all the bucket sockets, > and then release the bucket lock. This enables BPF or kernel helpers to > skip sock locking when invoked in the supported BPF contexts. > The batching logic is similar to the logic implemented in TCP iterator: > https://lore.kernel.org/bpf/20210701200613.1036157-1-kafai@fb.com/. > Suggested-by: Martin KaFai Lau > Signed-off-by: Aditi Ghag > --- > net/ipv4/udp.c | 224 +++++++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 215 insertions(+), 9 deletions(-) > diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c > index c605d171eb2d..2f3978de45f2 100644 > --- a/net/ipv4/udp.c > +++ b/net/ipv4/udp.c > @@ -3152,6 +3152,141 @@ struct bpf_iter__udp { > int bucket __aligned(8); > }; > +struct bpf_udp_iter_state { > + struct udp_iter_state state; [..] > + unsigned int cur_sk; > + unsigned int end_sk; > + unsigned int max_sk; > + struct sock **batch; > + bool st_bucket_done; Any change we can generalize some of those across tcp & udp? I haven't looked too deep, but a lot of things look like a plain copy-paste from tcp batching. Or not worth it? > +}; > + > +static unsigned short seq_file_family(const struct seq_file *seq); > +static int bpf_iter_udp_realloc_batch(struct bpf_udp_iter_state *iter, > + unsigned int new_batch_sz); > + > +static inline bool seq_sk_match(struct seq_file *seq, const struct sock > *sk) > +{ > + unsigned short family = seq_file_family(seq); > + > + /* AF_UNSPEC is used as a match all */ > + return ((family == AF_UNSPEC || family == sk->sk_family) && > + net_eq(sock_net(sk), seq_file_net(seq))); > +} > + > +static struct sock *bpf_iter_udp_batch(struct seq_file *seq) > +{ > + struct bpf_udp_iter_state *iter = seq->private; > + struct udp_iter_state *state = &iter->state; > + struct net *net = seq_file_net(seq); > + struct udp_seq_afinfo *afinfo = state->bpf_seq_afinfo; > + struct udp_table *udptable; > + struct sock *first_sk = NULL; > + struct sock *sk; > + unsigned int bucket_sks = 0; > + bool first; > + bool resized = false; > + > + /* The current batch is done, so advance the bucket. */ > + if (iter->st_bucket_done) > + state->bucket++; > + > + udptable = udp_get_table_afinfo(afinfo, net); > + > +again: > + /* New batch for the next bucket. > + * Iterate over the hash table to find a bucket with sockets matching > + * the iterator attributes, and return the first matching socket from > + * the bucket. The remaining matched sockets from the bucket are batched > + * before releasing the bucket lock. This allows BPF programs that are > + * called in seq_show to acquire the bucket lock if needed. > + */ > + iter->cur_sk = 0; > + iter->end_sk = 0; > + iter->st_bucket_done = false; > + first = true; > + > + for (; state->bucket <= udptable->mask; state->bucket++) { > + struct udp_hslot *hslot = &udptable->hash[state->bucket]; > + > + if (hlist_empty(&hslot->head)) > + continue; > + > + spin_lock_bh(&hslot->lock); > + sk_for_each(sk, &hslot->head) { > + if (seq_sk_match(seq, sk)) { > + if (first) { > + first_sk = sk; > + first = false; > + } > + if (iter->end_sk < iter->max_sk) { > + sock_hold(sk); > + iter->batch[iter->end_sk++] = sk; > + } > + bucket_sks++; > + } > + } > + spin_unlock_bh(&hslot->lock); > + if (first_sk) > + break; > + } > + > + /* All done: no batch made. */ > + if (!first_sk) > + return NULL; > + > + if (iter->end_sk == bucket_sks) { > + /* Batching is done for the current bucket; return the first > + * socket to be iterated from the batch. > + */ > + iter->st_bucket_done = true; > + return first_sk; > + } > + if (!resized && !bpf_iter_udp_realloc_batch(iter, bucket_sks * 3 / 2)) { > + resized = true; > + /* Go back to the previous bucket to resize its batch. */ > + state->bucket--; > + goto again; > + } > + return first_sk; > +} > + > +static void *bpf_iter_udp_seq_next(struct seq_file *seq, void *v, loff_t > *pos) > +{ > + struct bpf_udp_iter_state *iter = seq->private; > + struct sock *sk; > + > + /* Whenever seq_next() is called, the iter->cur_sk is > + * done with seq_show(), so unref the iter->cur_sk. > + */ > + if (iter->cur_sk < iter->end_sk) > + sock_put(iter->batch[iter->cur_sk++]); > + > + /* After updating iter->cur_sk, check if there are more sockets > + * available in the current bucket batch. > + */ > + if (iter->cur_sk < iter->end_sk) { > + sk = iter->batch[iter->cur_sk]; > + } else { > + // Prepare a new batch. > + sk = bpf_iter_udp_batch(seq); > + } > + > + ++*pos; > + return sk; > +} > + > +static void *bpf_iter_udp_seq_start(struct seq_file *seq, loff_t *pos) > +{ > + /* bpf iter does not support lseek, so it always > + * continue from where it was stop()-ped. > + */ > + if (*pos) > + return bpf_iter_udp_batch(seq); > + > + return SEQ_START_TOKEN; > +} > + > static int udp_prog_seq_show(struct bpf_prog *prog, struct bpf_iter_meta > *meta, > struct udp_sock *udp_sk, uid_t uid, int bucket) > { > @@ -3172,18 +3307,34 @@ static int bpf_iter_udp_seq_show(struct seq_file > *seq, void *v) > struct bpf_prog *prog; > struct sock *sk = v; > uid_t uid; > + bool slow; > + int rc; > if (v == SEQ_START_TOKEN) > return 0; > + slow = lock_sock_fast(sk); Hm, I missed the fact that we're already using fast lock in the tcp batching as well. Should we not use fask locks here? On a loaded system it's probably fair to pay some backlog processing in the path that goes over every socket (here)? Martin, WDYT? > + > + if (unlikely(sk_unhashed(sk))) { > + rc = SEQ_SKIP; > + goto unlock; > + } > + > uid = from_kuid_munged(seq_user_ns(seq), sock_i_uid(sk)); > meta.seq = seq; > prog = bpf_iter_get_info(&meta, false); > - return udp_prog_seq_show(prog, &meta, v, uid, state->bucket); > + rc = udp_prog_seq_show(prog, &meta, v, uid, state->bucket); > + > +unlock: > + unlock_sock_fast(sk, slow); > + return rc; > } > +static void bpf_iter_udp_unref_batch(struct bpf_udp_iter_state *iter); Why forward declaration? Why not define the function here? > + > static void bpf_iter_udp_seq_stop(struct seq_file *seq, void *v) > { > + struct bpf_udp_iter_state *iter = seq->private; > struct bpf_iter_meta meta; > struct bpf_prog *prog; > @@ -3194,15 +3345,31 @@ static void bpf_iter_udp_seq_stop(struct seq_file > *seq, void *v) > (void)udp_prog_seq_show(prog, &meta, v, 0, 0); > } > - udp_seq_stop(seq, v); > + if (iter->cur_sk < iter->end_sk) { > + bpf_iter_udp_unref_batch(iter); > + iter->st_bucket_done = false; > + } > } > static const struct seq_operations bpf_iter_udp_seq_ops = { > - .start = udp_seq_start, > - .next = udp_seq_next, > + .start = bpf_iter_udp_seq_start, > + .next = bpf_iter_udp_seq_next, > .stop = bpf_iter_udp_seq_stop, > .show = bpf_iter_udp_seq_show, > }; > + > +static unsigned short seq_file_family(const struct seq_file *seq) > +{ > + const struct udp_seq_afinfo *afinfo; > + > + /* BPF iterator: bpf programs to filter sockets. */ > + if (seq->op == &bpf_iter_udp_seq_ops) > + return AF_UNSPEC; > + > + /* Proc fs iterator */ > + afinfo = pde_data(file_inode(seq->file)); > + return afinfo->family; > +} > #endif > const struct seq_operations udp_seq_ops = { > @@ -3413,9 +3580,38 @@ static struct pernet_operations __net_initdata > udp_sysctl_ops = { > DEFINE_BPF_ITER_FUNC(udp, struct bpf_iter_meta *meta, > struct udp_sock *udp_sk, uid_t uid, int bucket) > +static void bpf_iter_udp_unref_batch(struct bpf_udp_iter_state *iter) > +{ > + while (iter->cur_sk < iter->end_sk) > + sock_put(iter->batch[iter->cur_sk++]); > +} > + > +static int bpf_iter_udp_realloc_batch(struct bpf_udp_iter_state *iter, > + unsigned int new_batch_sz) > +{ > + struct sock **new_batch; > + > + new_batch = kvmalloc_array(new_batch_sz, sizeof(*new_batch), > + GFP_USER | __GFP_NOWARN); > + if (!new_batch) > + return -ENOMEM; > + > + bpf_iter_udp_unref_batch(iter); > + kvfree(iter->batch); > + iter->batch = new_batch; > + iter->max_sk = new_batch_sz; > + > + return 0; > +} > + > +#define INIT_BATCH_SZ 16 > + > +static void bpf_iter_fini_udp(void *priv_data); > + > static int bpf_iter_init_udp(void *priv_data, struct bpf_iter_aux_info > *aux) > { > - struct udp_iter_state *st = priv_data; > + struct bpf_udp_iter_state *iter = priv_data; > + struct udp_iter_state *st = &iter->state; > struct udp_seq_afinfo *afinfo; > int ret; > @@ -3427,24 +3623,34 @@ static int bpf_iter_init_udp(void *priv_data, > struct bpf_iter_aux_info *aux) > afinfo->udp_table = NULL; > st->bpf_seq_afinfo = afinfo; > ret = bpf_iter_init_seq_net(priv_data, aux); > - if (ret) > + if (ret) { > kfree(afinfo); > + return ret; > + } > + ret = bpf_iter_udp_realloc_batch(iter, INIT_BATCH_SZ); > + if (ret) { > + bpf_iter_fini_seq_net(priv_data); Leaking afinfo here? Since we are not feeing it from bpf_iter_fini_udp any more? (why?) > + return ret; > + } > + iter->cur_sk = 0; > + iter->end_sk = 0; > + > return ret; > } > static void bpf_iter_fini_udp(void *priv_data) > { > - struct udp_iter_state *st = priv_data; > + struct bpf_udp_iter_state *iter = priv_data; > - kfree(st->bpf_seq_afinfo); > bpf_iter_fini_seq_net(priv_data); > + kfree(iter->batch); > } > static const struct bpf_iter_seq_info udp_seq_info = { > .seq_ops = &bpf_iter_udp_seq_ops, > .init_seq_private = bpf_iter_init_udp, > .fini_seq_private = bpf_iter_fini_udp, > - .seq_priv_size = sizeof(struct udp_iter_state), > + .seq_priv_size = sizeof(struct bpf_udp_iter_state), > }; > static struct bpf_iter_reg udp_reg_info = { > -- > 2.34.1