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charset="us-ascii" Content-ID: <14E3BE765900B044A72996E5A34BBC59@namprd15.prod.outlook.com> MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SA1PR15MB5109.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 2604e7de-b64b-49a3-75db-08d9748ecb6a X-MS-Exchange-CrossTenant-originalarrivaltime: 10 Sep 2021 19:11:29.5176 (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: gXU+gIkqSNfxeEJcUkaFIO9yvQxIFbhCmRyUtkHO/u4z4yyxN0/S+vsOioOk7ql+eEOWNitMNncY6ktjKBHmdA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR15MB5063 X-OriginatorOrg: fb.com X-Proofpoint-ORIG-GUID: Wt51SO8brCkhi3DvdbDS9p7c6zwBgLVR X-Proofpoint-GUID: Wt51SO8brCkhi3DvdbDS9p7c6zwBgLVR X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-09-10_07:2021-09-09,2021-09-10 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=0 bulkscore=0 mlxlogscore=956 impostorscore=0 malwarescore=0 adultscore=0 mlxscore=0 lowpriorityscore=0 phishscore=0 priorityscore=1501 clxscore=1015 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109030001 definitions=main-2109100111 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Sep 10, 2021, at 12:08 PM, Peter Zijlstra wrote: > > On Fri, Sep 10, 2021 at 07:00:08PM +0000, Song Liu wrote: > >> Hmm.. not really. We call migrate_disable() before entering the BPF program. >> And the helper calls snapshot_branch_stack() inside the BPF program. To move >> it to before migrate_disable(), we will have to add a "whether to snapshot >> branch stack" check before entering the BPF program. This check, while is >> cheap, is added to all BPF programs on this hook, even when the program does >> not use snapshot at all. So we would rather keep all logic inside the helper, >> and not touch the common path. > > Moo :/ Because I also really don't want to expose struct rq, it's > currently nicely squirelled away in kernel/sched/ and doesn't get > anywhere near include/. This matches my guess, so I didn't go too far on that direction. :-) > > A well, maybe we can do something clever with migrate_disable() itself. > I'll put it on this endless todo list ;-) Awesome! Thanks, Song