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Wed, 16 Dec 2020 17:35:58 +0000 From: Song Liu To: Yonghong Song CC: bpf , "netdev@vger.kernel.org" , "ast@kernel.org" , "daniel@iogearbox.net" , "andrii@kernel.org" , "john.fastabend@gmail.com" , "kpsingh@chromium.org" , Kernel Team Subject: Re: [PATCH v2 bpf-next 0/4] introduce bpf_iter for task_vma Thread-Topic: [PATCH v2 bpf-next 0/4] introduce bpf_iter for task_vma Thread-Index: AQHW0zs5Zgx5qG7e7kmzUIj70BsWzan581cAgAAKBYA= Date: Wed, 16 Dec 2020 17:35:58 +0000 Message-ID: <192C599B-7ED6-47A5-BF83-FA25655EAE88@fb.com> References: <20201215233702.3301881-1-songliubraving@fb.com> <7032f6a9-ec51-51b0-8981-bdfda1aad5b6@fb.com> In-Reply-To: <7032f6a9-ec51-51b0-8981-bdfda1aad5b6@fb.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3608.120.23.2.4) x-originating-ip: [2620:10d:c091:480::1:e346] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 7c64c706-8f0d-464b-9166-08d8a1e90ce6 x-ms-traffictypediagnostic: BYAPR15MB2582: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-fb-source: Internal x-ms-oob-tlc-oobclassifiers: OLM:9508; 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charset="us-ascii" Content-ID: <10EF933F6C65FC42895392D2B5595E06@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: BYAPR15MB2999.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 7c64c706-8f0d-464b-9166-08d8a1e90ce6 X-MS-Exchange-CrossTenant-originalarrivaltime: 16 Dec 2020 17:35:58.7914 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: prrBuGYsbP9WKuveHfzeh0QGatbbWgeo8LSoD1dwbW1L9shpg8O7WCr40WyypVWuuormcwJWNsP7CHFmyLeofg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2582 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.343,18.0.737 definitions=2020-12-16_07:2020-12-15,2020-12-16 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 lowpriorityscore=0 adultscore=0 impostorscore=0 suspectscore=0 malwarescore=0 spamscore=0 clxscore=1015 mlxscore=0 phishscore=0 mlxlogscore=927 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2012160113 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org > On Dec 16, 2020, at 9:00 AM, Yonghong Song wrote: >=20 >=20 >=20 > 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 >=20 > 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 inf= ormation require architecture and configuration specific logic, e.g., page table str= ucture.=20 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 i= s most useful in gathering information that are not presented in smaps. For exampl= e, if a vma covers mixed 2MB pages and 4kB pages, smaps won't show which address ra= nges are backed by 2MB pages.=20 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 f= or too big vma. We can probably add this program to samples/bpf/, but I think it i= s not a good fit for selftests.=20 Thanks, Song=20