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charset="us-ascii" Content-ID: <2502B153EE41264C8678F5858028E5D9@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 4ab3c9f5-681b-4ac5-3472-08d766c5acd6 X-MS-Exchange-CrossTenant-originalarrivaltime: 11 Nov 2019 16:39:08.9394 (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: vx7mZC/e3Uy8FFa65KBXVHCTXH8zArMJsJIaE3T1fB1I355VTYo9l4fWmCYKR6tW3bMkNVTyNY0H0mtWfu1CcQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR15MB1311 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-11-11_05:2019-11-11,2019-11-11 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 adultscore=0 phishscore=0 mlxlogscore=999 priorityscore=1501 malwarescore=0 lowpriorityscore=0 spamscore=0 suspectscore=0 mlxscore=0 impostorscore=0 bulkscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1911110151 X-FB-Internal: deliver Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org > On Nov 8, 2019, at 11:34 AM, Andrii Nakryiko = wrote: >=20 > On Thu, Nov 7, 2019 at 10:39 PM Song Liu wrote: >>=20 >>=20 >>=20 >>> On Nov 7, 2019, at 8:20 PM, Andrii Nakryiko wrote: >>>=20 >>> Add ability to memory-map contents of BPF array map. This is extremely = useful >>> for working with BPF global data from userspace programs. It allows to = avoid >>> typical bpf_map_{lookup,update}_elem operations, improving both perform= ance >>> and usability. >>>=20 >>> There had to be special considerations for map freezing, to avoid havin= g >>> writable memory view into a frozen map. To solve this issue, map freezi= ng and >>> mmap-ing is happening under mutex now: >>> - if map is already frozen, no writable mapping is allowed; >>> - if map has writable memory mappings active (accounted in map->writecn= t), >>> map freezing will keep failing with -EBUSY; >>> - once number of writable memory mappings drops to zero, map freezing c= an be >>> performed again. >>>=20 >>> Only non-per-CPU arrays are supported right now. Maps with spinlocks ca= n't be >>> memory mapped either. >>>=20 >>> Cc: Rik van Riel >>> Cc: Johannes Weiner >>> Signed-off-by: Andrii Nakryiko >>=20 >> Acked-by: Song Liu >>=20 >> With one nit below. >>=20 >>=20 >> [...] >>=20 >>> - if (percpu) >>> + data_size =3D 0; >>> + if (percpu) { >>> array_size +=3D (u64) max_entries * sizeof(void *); >>> - else >>> - array_size +=3D (u64) max_entries * elem_size; >>=20 >>> + } else { >>> + if (attr->map_flags & BPF_F_MMAPABLE) { >>> + data_size =3D (u64) max_entries * elem_size; >>> + data_size =3D round_up(data_size, PAGE_SIZE); >>> + } else { >>> + array_size +=3D (u64) max_entries * elem_size; >>> + } >>> + } >>>=20 >>> /* make sure there is no u32 overflow later in round_up() */ >>> - cost =3D array_size; >>> + cost =3D array_size + data_size; >>=20 >>=20 >>=20 >> This is a little confusing. Maybe we can do >>=20 >=20 > I don't think I can do that without even bigger code churn. In > non-mmap()-able case, array_size specifies the size of one chunk of > memory, which consists of sizeof(struct bpf_array) bytes, followed by > actual data. This is accomplished in one allocation. That's current > case for arrays. >=20 > For BPF_F_MMAPABLE case, though, we have to do 2 separate allocations, > to make sure that mmap()-able part is allocated with vmalloc() and is > page-aligned. So array_size keeps track of number of bytes allocated > for struct bpf_array plus, optionally, per-cpu or non-mmapable array > data, while data_size is explicitly for vmalloc()-ed mmap()-able chunk > of data. If not for this, I'd just keep adjusting array_size. >=20 > So the invariant for per-cpu and non-mmapable case is that data_size =3D > 0, array_size =3D sizeof(struct bpf_array) + whatever amount of data we > need. For mmapable case: array_size =3D sizeof(struct bpf_array), > data_size =3D actual amount of array data. I see. Thanks for the explanation.=20 Song