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 957E6C433F5 for ; Wed, 23 Feb 2022 03:13:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236279AbiBWDNk (ORCPT ); Tue, 22 Feb 2022 22:13:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56494 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235329AbiBWDNk (ORCPT ); Tue, 22 Feb 2022 22:13:40 -0500 Received: from mail-pg1-x541.google.com (mail-pg1-x541.google.com [IPv6:2607:f8b0:4864:20::541]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5591F13E1D; Tue, 22 Feb 2022 19:13:13 -0800 (PST) Received: by mail-pg1-x541.google.com with SMTP id p23so18709783pgj.2; Tue, 22 Feb 2022 19:13:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=WZwjjjbdPFprQvSvMzO5H1FigoEjlfzPO+BSIT/kEXQ=; b=Gc/K17z0Y/i0uHMsdCvSGHIaaqgP5ilq+Yfn2v9UE69EBkYQqx+rWwHRMm/LABoazC oF/XBnTfn22+f0N9Rb0DpSJjoJ22SMUVLpKqI6eNdcQ3qx0P9BnCUzkZr91WqxV3xBUA o+0BVfKaCtll97mWbHn+uN3o/segrsn/gTaD6E0m+di+qfykJw1G/NLEOkNtcZ0JyYL1 H0EVbhTOFWRjc2/NRmXo5JCgVTG/bOcnQ6o5CdBxlG7xfyPyQeIeXLHzJmjW1E+3gYnp 2swbTcDBhX736QG7tgS+8F0UIggYVPQ9cZFwTUZPSJqYhLSRHCIsbmmiKdrYnwnqDdWz xqTQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=WZwjjjbdPFprQvSvMzO5H1FigoEjlfzPO+BSIT/kEXQ=; b=Wi2iJInXwx9ai3R0+/q5hdLLjiWhDzd220AIIEG9lpkUS2md4Z/kyLZ56smfcXe6TA H5MWMvEncXqHUO32JIUoQVenNOlMokqSb/Q9PMeiEweoB4ufNk64IEUDgOONK3tTju/9 Kjz/WaFpITRNkszZOuGsJ0mR+arn4Ag6UnyNk9JPaVgBFdt9wcpjHIR2BtqyfjGrdkz8 TdrCY4PmJ7qY0/6PxI/bpMvjzRun0WOXnUfmtp7z28/U1J3v+SxCMtcYjsRIGvd7rca8 c8IcPMwWgEtpe08mtrk/CjczG2jLfrbQBEulcNJB8dUgBLF3sx/NcolBMKTGxOtrle6f du1w== X-Gm-Message-State: AOAM531x74lkFvVtP6EvVn0s8F/AjqBR9J8H+BBIFoAMpcPMd0kmoRUd fLiTNsO88jTos65ekjC8dOA= X-Google-Smtp-Source: ABdhPJwHJg9BDkF3j99zuqO5zuNQoVwu4uqGdL+HfJIKsyYXxG+CUyeIvMpkyEEP6ZsZbjeAKt0EZg== X-Received: by 2002:a05:6a00:8d5:b0:4e1:77c9:def8 with SMTP id s21-20020a056a0008d500b004e177c9def8mr27806777pfu.55.1645585992782; Tue, 22 Feb 2022 19:13:12 -0800 (PST) Received: from localhost ([2405:201:6014:d0c0:6243:316e:a9e1:adda]) by smtp.gmail.com with ESMTPSA id q8sm18131729pfk.168.2022.02.22.19.13.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Feb 2022 19:13:12 -0800 (PST) Date: Wed, 23 Feb 2022 08:43:10 +0530 From: Kumar Kartikeya Dwivedi To: Alexei Starovoitov Cc: bpf@vger.kernel.org, Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= , Jesper Dangaard Brouer , netfilter-devel@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH bpf-next v1 08/15] bpf: Adapt copy_map_value for multiple offset case Message-ID: <20220223031310.d2jh4uwffn3jzoy4@apollo.legion> References: <20220220134813.3411982-1-memxor@gmail.com> <20220220134813.3411982-9-memxor@gmail.com> <20220222070405.i6esgcf7ouqrmoef@ast-mbp.dhcp.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220222070405.i6esgcf7ouqrmoef@ast-mbp.dhcp.thefacebook.com> Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Feb 22, 2022 at 12:34:05PM IST, Alexei Starovoitov wrote: > On Sun, Feb 20, 2022 at 07:18:06PM +0530, Kumar Kartikeya Dwivedi wrote: > > The changes in this patch deserve closer look, so it has been split into > > its own independent patch. While earlier we just had to skip two objects > > at most while copying in and out of map, now we have potentially many > > objects (at most 8 + 2 = 10, due to the BPF_MAP_VALUE_OFF_MAX limit). > > > > Hence, divide the copy_map_value function into an inlined fast path and > > function call to slowpath. The slowpath handles the case of > 3 offsets, > > while we handle the most common cases (0, 1, 2, or 3 offsets) in the > > inline function itself. > > > > In copy_map_value_slow, we use 11 offsets, just to make the for loop > > that copies the value free of edge cases for the last offset, by using > > map->value_size as final offset to subtract remaining area to copy from. > > > > Signed-off-by: Kumar Kartikeya Dwivedi > > --- > > include/linux/bpf.h | 43 +++++++++++++++++++++++++++++++--- > > kernel/bpf/syscall.c | 55 ++++++++++++++++++++++++++++++++++++++++++++ > > 2 files changed, 95 insertions(+), 3 deletions(-) > > > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > > index ae599aaf8d4c..5d845ca02eba 100644 > > --- a/include/linux/bpf.h > > +++ b/include/linux/bpf.h > > @@ -253,12 +253,22 @@ static inline void check_and_init_map_value(struct bpf_map *map, void *dst) > > memset(dst + map->spin_lock_off, 0, sizeof(struct bpf_spin_lock)); > > if (unlikely(map_value_has_timer(map))) > > memset(dst + map->timer_off, 0, sizeof(struct bpf_timer)); > > + if (unlikely(map_value_has_ptr_to_btf_id(map))) { > > + struct bpf_map_value_off *tab = map->ptr_off_tab; > > + int i; > > + > > + for (i = 0; i < tab->nr_off; i++) > > + *(u64 *)(dst + tab->off[i].offset) = 0; > > + } > > } > > > > +void copy_map_value_slow(struct bpf_map *map, void *dst, void *src, u32 s_off, > > + u32 s_sz, u32 t_off, u32 t_sz); > > + > > /* copy everything but bpf_spin_lock and bpf_timer. There could be one of each. */ > > static inline void copy_map_value(struct bpf_map *map, void *dst, void *src) > > { > > - u32 s_off = 0, s_sz = 0, t_off = 0, t_sz = 0; > > + u32 s_off = 0, s_sz = 0, t_off = 0, t_sz = 0, p_off = 0, p_sz = 0; > > > > if (unlikely(map_value_has_spin_lock(map))) { > > s_off = map->spin_lock_off; > > @@ -268,13 +278,40 @@ static inline void copy_map_value(struct bpf_map *map, void *dst, void *src) > > t_off = map->timer_off; > > t_sz = sizeof(struct bpf_timer); > > } > > + /* Multiple offset case is slow, offload to function */ > > + if (unlikely(map_value_has_ptr_to_btf_id(map))) { > > + struct bpf_map_value_off *tab = map->ptr_off_tab; > > + > > + /* Inline the likely common case */ > > + if (likely(tab->nr_off == 1)) { > > + p_off = tab->off[0].offset; > > + p_sz = sizeof(u64); > > + } else { > > + copy_map_value_slow(map, dst, src, s_off, s_sz, t_off, t_sz); > > + return; > > + } > > + } > > + > > + if (unlikely(s_sz || t_sz || p_sz)) { > > + /* The order is p_off, t_off, s_off, use insertion sort */ > > > > - if (unlikely(s_sz || t_sz)) { > > + if (t_off < p_off || !t_sz) { > > + swap(t_off, p_off); > > + swap(t_sz, p_sz); > > + } > > if (s_off < t_off || !s_sz) { > > swap(s_off, t_off); > > swap(s_sz, t_sz); > > + if (t_off < p_off || !t_sz) { > > + swap(t_off, p_off); > > + swap(t_sz, p_sz); > > + } > > } > > - memcpy(dst, src, t_off); > > + > > + memcpy(dst, src, p_off); > > + memcpy(dst + p_off + p_sz, > > + src + p_off + p_sz, > > + t_off - p_off - p_sz); > > memcpy(dst + t_off + t_sz, > > src + t_off + t_sz, > > s_off - t_off - t_sz); > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > > index beb96866f34d..83d71d6912f5 100644 > > --- a/kernel/bpf/syscall.c > > +++ b/kernel/bpf/syscall.c > > @@ -30,6 +30,7 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > #include > > @@ -230,6 +231,60 @@ static int bpf_map_update_value(struct bpf_map *map, struct fd f, void *key, > > return err; > > } > > > > +static int copy_map_value_cmp(const void *_a, const void *_b) > > +{ > > + const u32 a = *(const u32 *)_a; > > + const u32 b = *(const u32 *)_b; > > + > > + /* We only need to sort based on offset */ > > + if (a < b) > > + return -1; > > + else if (a > b) > > + return 1; > > + return 0; > > +} > > + > > +void copy_map_value_slow(struct bpf_map *map, void *dst, void *src, u32 s_off, > > + u32 s_sz, u32 t_off, u32 t_sz) > > +{ > > + struct bpf_map_value_off *tab = map->ptr_off_tab; /* already set to non-NULL */ > > + /* 3 = 2 for bpf_timer, bpf_spin_lock, 1 for map->value_size sentinel */ > > + struct { > > + u32 off; > > + u32 sz; > > + } off_arr[BPF_MAP_VALUE_OFF_MAX + 3]; > > + int i, cnt = 0; > > + > > + /* Reconsider stack usage when bumping BPF_MAP_VALUE_OFF_MAX */ > > + BUILD_BUG_ON(sizeof(off_arr) != 88); > > + > > + for (i = 0; i < tab->nr_off; i++) { > > + off_arr[cnt].off = tab->off[i].offset; > > + off_arr[cnt++].sz = sizeof(u64); > > + } > > + if (s_sz) { > > + off_arr[cnt].off = s_off; > > + off_arr[cnt++].sz = s_sz; > > + } > > + if (t_sz) { > > + off_arr[cnt].off = t_off; > > + off_arr[cnt++].sz = t_sz; > > + } > > + off_arr[cnt].off = map->value_size; > > + > > + sort(off_arr, cnt, sizeof(off_arr[0]), copy_map_value_cmp, NULL); > > Ouch. sort every time we need to copy map value? > sort it once please. 88 bytes in a map are worth it. > Especially since "slow" version will trigger with just 2 kptrs. > (if I understand this correctly). Ok, also think we can reduce the size of the 88 bytes down to 55 bytes (32-bit off + 8-bit size), and embed it in struct map. Then the shuffling needed for timer and spin lock should also be gone. -- Kartikeya