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From: Song Liu <songliubraving@fb.com>
To: Yonghong Song <yhs@fb.com>
Cc: bpf <bpf@vger.kernel.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"ast@kernel.org" <ast@kernel.org>,
	"daniel@iogearbox.net" <daniel@iogearbox.net>,
	"andrii@kernel.org" <andrii@kernel.org>,
	"john.fastabend@gmail.com" <john.fastabend@gmail.com>,
	"kpsingh@chromium.org" <kpsingh@chromium.org>,
	Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH v2 bpf-next 0/4] introduce bpf_iter for task_vma
Date: Wed, 16 Dec 2020 17:35:58 +0000	[thread overview]
Message-ID: <192C599B-7ED6-47A5-BF83-FA25655EAE88@fb.com> (raw)
In-Reply-To: <7032f6a9-ec51-51b0-8981-bdfda1aad5b6@fb.com>



> On Dec 16, 2020, at 9:00 AM, Yonghong Song <yhs@fb.com> wrote:
> 
> 
> 
> On 12/15/20 3:36 PM, Song Liu wrote:
>> This set introduces bpf_iter for task_vma, which can be used to generate
>> information similar to /proc/pid/maps or /proc/pid/smaps. Patch 4/4 adds
> 
> I did not see an example for /proc/pid/smaps. It would be good if you can cover smaps as well since it is used by a lot of people.

smaps is tricky, as it contains a lot of information, and some of these information
require architecture and configuration specific logic, e.g., page table structure. 
To really mimic smaps, we will probably need a helper for smap_gather_stats().
However, I don't think that's really necessary. I think task_vma iterator is most
useful in gathering information that are not presented in smaps. For example, if a
vma covers mixed 2MB pages and 4kB pages, smaps won't show which address ranges are
backed by 2MB pages. 

I have a test BPF program that parses 4-level x86 page table for huge pages. Since
we need bounded-loop to parse the page table, the program won't work well for too
big vma. We can probably add this program to samples/bpf/, but I think it is not
a good fit for selftests. 

Thanks,
Song 


  reply	other threads:[~2020-12-16 17:37 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-15 23:36 [PATCH v2 bpf-next 0/4] introduce bpf_iter for task_vma Song Liu
2020-12-15 23:36 ` [PATCH v2 bpf-next 1/4] bpf: introduce task_vma bpf_iter Song Liu
2020-12-16 17:36   ` Yonghong Song
2020-12-16 19:41     ` Song Liu
2020-12-17  0:34   ` Andrii Nakryiko
2020-12-17  1:51     ` Song Liu
2020-12-17 19:03   ` Alexei Starovoitov
2020-12-17 22:08     ` Song Liu
2020-12-18  2:34       ` Alexei Starovoitov
2020-12-18  3:15         ` Yonghong Song
2020-12-18  4:33         ` Song Liu
2020-12-18  5:23           ` Alexei Starovoitov
2020-12-18 16:38             ` Yonghong Song
2020-12-18 17:23               ` Song Liu
2021-01-05  1:46                 ` Alexei Starovoitov
2021-01-05  5:47                   ` Song Liu
2021-01-05 16:27                     ` Alexei Starovoitov
2021-01-05 17:10                       ` Song Liu
2021-01-05 17:27                         ` Alexei Starovoitov
2021-01-05 19:38                           ` Song Liu
2021-01-05 19:46                             ` Alexei Starovoitov
2021-01-05 19:51                               ` Song Liu
2020-12-15 23:37 ` [PATCH v2 bpf-next 2/4] bpf: allow bpf_d_path in sleepable bpf_iter program Song Liu
2020-12-16 17:41   ` Yonghong Song
2020-12-16 18:15   ` KP Singh
2020-12-16 18:31     ` KP Singh
2021-01-25 12:52   ` Jiri Olsa
2020-12-15 23:37 ` [PATCH v2 bpf-next 3/4] libbpf: introduce section "iter.s/" for " Song Liu
2020-12-16 17:42   ` Yonghong Song
2020-12-16 18:00     ` KP Singh
2020-12-15 23:37 ` [PATCH v2 bpf-next 4/4] selftests/bpf: add test for bpf_iter_task_vma Song Liu
2020-12-16 18:18   ` Yonghong Song
2020-12-16 23:23     ` Song Liu
2020-12-16 17:00 ` [PATCH v2 bpf-next 0/4] introduce bpf_iter for task_vma Yonghong Song
2020-12-16 17:35   ` Song Liu [this message]
2020-12-16 18:31     ` Yonghong Song

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