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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Jiri Olsa <jolsa@kernel.org>
Cc: "Alexei Starovoitov" <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Song Liu" <songliubraving@fb.com>,
	netdev@vger.kernel.org, bpf@vger.kernel.org,
	"Andrii Nakryiko" <andriin@fb.com>, "Yonghong Song" <yhs@fb.com>,
	"Martin KaFai Lau" <kafai@fb.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"David Miller" <davem@redhat.com>,
	"Björn Töpel" <bjorn.topel@intel.com>,
	"John Fastabend" <john.fastabend@gmail.com>,
	"Jesper Dangaard Brouer" <hawk@kernel.org>,
	"Arnaldo Carvalho de Melo" <acme@redhat.com>,
	"Song Liu" <song@kernel.org>
Subject: Re: [PATCH 06/15] bpf: Add bpf_ksym_tree tree
Date: Tue, 3 Mar 2020 10:03:19 -0800	[thread overview]
Message-ID: <20200303180318.vblj7izq2miken6e@ast-mbp> (raw)
In-Reply-To: <20200302143154.258569-7-jolsa@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.

  reply	other threads:[~2020-03-03 18:03 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-02 14:31 [PATCHv4 00/15] bpf: Add trampoline and dispatcher to /proc/kallsyms Jiri Olsa
2020-03-02 14:31 ` [PATCH 01/15] x86/mm: Rename is_kernel_text to __is_kernel_text Jiri Olsa
2020-03-02 14:31 ` [PATCH 02/15] bpf: Add bpf_trampoline_ name prefix for DECLARE_BPF_DISPATCHER Jiri Olsa
2020-03-02 14:31 ` [PATCH 03/15] bpf: Add struct bpf_ksym Jiri Olsa
2020-03-02 14:31 ` [PATCH 04/15] bpf: Add name to " Jiri Olsa
2020-03-02 14:31 ` [PATCH 05/15] bpf: Move lnode list node " Jiri Olsa
2020-03-02 14:31 ` [PATCH 06/15] bpf: Add bpf_ksym_tree tree Jiri Olsa
2020-03-03 18:03   ` Alexei Starovoitov [this message]
2020-03-03 20:12     ` Jiri Olsa
2020-03-02 14:31 ` [PATCH 07/15] bpf: Move bpf_tree add/del from bpf_prog_ksym_node_add/del Jiri Olsa
2020-03-02 14:31 ` [PATCH 08/15] bpf: Separate kallsyms add/del functions Jiri Olsa
2020-03-02 14:31 ` [PATCH 09/15] bpf: Add bpf_ksym_add/del functions Jiri Olsa
2020-03-02 14:31 ` [PATCH 10/15] bpf: Rename bpf_tree to bpf_progs_tree Jiri Olsa
2020-03-02 14:31 ` [PATCH 11/15] bpf: Add trampolines to kallsyms Jiri Olsa
2020-03-02 14:31 ` [PATCH 12/15] bpf: Add dispatchers " Jiri Olsa
2020-03-02 14:31 ` [PATCH 13/15] perf tools: Synthesize bpf_trampoline/dispatcher ksymbol event Jiri Olsa
2020-03-02 14:31 ` [PATCH 14/15] perf tools: Set ksymbol dso as loaded on arrival Jiri Olsa
2020-03-02 14:31 ` [PATCH 15/15] perf annotate: Add base support for bpf_image Jiri Olsa

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