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Tue, 03 Mar 2020 10:03:22 -0800 (PST) Received: from ast-mbp ([2620:10d:c090:500::4:a0de]) by smtp.gmail.com with ESMTPSA id b4sm26257540pfd.18.2020.03.03.10.03.20 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 03 Mar 2020 10:03:21 -0800 (PST) Date: Tue, 3 Mar 2020 10:03:19 -0800 From: Alexei Starovoitov To: Jiri Olsa Cc: Alexei Starovoitov , Daniel Borkmann , Song Liu , netdev@vger.kernel.org, bpf@vger.kernel.org, Andrii Nakryiko , Yonghong Song , Martin KaFai Lau , Jakub Kicinski , David Miller , =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= , John Fastabend , Jesper Dangaard Brouer , Arnaldo Carvalho de Melo , Song Liu Subject: Re: [PATCH 06/15] bpf: Add bpf_ksym_tree tree Message-ID: <20200303180318.vblj7izq2miken6e@ast-mbp> References: <20200302143154.258569-1-jolsa@kernel.org> <20200302143154.258569-7-jolsa@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200302143154.258569-7-jolsa@kernel.org> User-Agent: NeoMutt/20180223 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Mar 02, 2020 at 03:31:45PM +0100, Jiri Olsa wrote: > The bpf_tree is used both for kallsyms iterations and searching > for exception tables of bpf programs, which is needed only for > bpf programs. > > Adding bpf_ksym_tree that will hold symbols for all bpf_prog > bpf_trampoline and bpf_dispatcher objects and keeping bpf_tree > only for bpf_prog objects to keep it fast. ... > static void bpf_prog_ksym_node_add(struct bpf_prog_aux *aux) > @@ -616,6 +650,7 @@ static void bpf_prog_ksym_node_add(struct bpf_prog_aux *aux) > WARN_ON_ONCE(!list_empty(&aux->ksym.lnode)); > list_add_tail_rcu(&aux->ksym.lnode, &bpf_kallsyms); > latch_tree_insert(&aux->ksym_tnode, &bpf_tree, &bpf_tree_ops); > + latch_tree_insert(&aux->ksym.tnode, &bpf_ksym_tree, &bpf_ksym_tree_ops); > } > > static void bpf_prog_ksym_node_del(struct bpf_prog_aux *aux) > @@ -624,6 +659,7 @@ static void bpf_prog_ksym_node_del(struct bpf_prog_aux *aux) > return; > > latch_tree_erase(&aux->ksym_tnode, &bpf_tree, &bpf_tree_ops); > + latch_tree_erase(&aux->ksym.tnode, &bpf_ksym_tree, &bpf_ksym_tree_ops); I have to agree with Daniel here. Having bpf prog in two latch trees is unnecessary. Especially looking at the patch 7 that moves update to the other tree. The whole thing becomes assymetrical and harder to follow. Consider that walking extable is slow anyway. It's a page fault. Having trampoline and dispatch in the same tree will not be measurable on the speed of search_bpf_extables->bpf_prog_kallsyms_find. So please consolidate. Also I don't see a hunk that deletes tnode from 'struct bpf_image'. These patches suppose to generalize it too, no? And at the end kernel_text_address() suppose to call is_bpf_text_address() only, right? Instead of is_bpf_text_address() || is_bpf_image_address() ? That _will_ actually speed up backtrace collection.