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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?M3yV+4x2IzR64oreuspmoI+fHvt8mNRY4WXY7LMiZqXYjKTuQ8MoxLBT9ruY?= =?us-ascii?Q?nSXyPCymKTeOOQNsMDX4MhnEWGZezttPUfiVJ5/B5PJsNas7Zc5+hiW2fZBc?= =?us-ascii?Q?k5XORZbXkPNj6TnwG4DH1YUNR/mlWF0Gf0ZgB3ugWBvmg0VrUhEVqF52bM05?= =?us-ascii?Q?hwdqeVBLAGFeZOhjsdWXmSJGcojeBtxrYTbdcqdET5XexWsLRvpd/SxAFOlI?= =?us-ascii?Q?B1UEFmEqRBjUHjVU+T2L93YLjjFsYFKetqRa16e5wtAk0mKO7koHmp4aFUxe?= =?us-ascii?Q?a6a1XR5nJVSnK0XG9aurETyBc2SbeOy9xy5hVH3ssX5sw9clcrymMloJ5mbt?= =?us-ascii?Q?d0wWUhhuP899KQWbLQSCVMSlS7SiKviB1XHTZL1adSN/LYSc5ZQa51TR7pxh?= =?us-ascii?Q?xYIKKmEZz9Ebb22aWMEHMn3esX5ofbh1T+8GxYyeZJZjye327J4MJEalJSlX?= =?us-ascii?Q?HbB5bJ0W5NEbZeF1Ptv8+ShQyNAtUMGHLnzH+YFRFCBJ0dXKTxCLHcsa2pVs?= =?us-ascii?Q?8OWZG7eSTzxElVsKF8KXOeWVLCHAJTJSyGMElEX/LiQHcA5JgOLzMat/k4WN?= =?us-ascii?Q?TGLnqbQIyYLIBuigNkUILdLnUyLPc77sVDbtNDVAkJDFnC9x/FhiAw3gkhXU?= =?us-ascii?Q?u0gBOooGaMOWND4QsmP8P5Os1cALNAcg2LZ/eOxqVNDRl/nAQoh5o8uAUjK1?= =?us-ascii?Q?A0tRNVHA6i8l4zjcjSevsouUuYVUv5QKsAzWp056ltsnBuQ3tyUslcDTE/hR?= =?us-ascii?Q?Bjit9gReCmz1PahPPr8fVVLOM7p3x/jQT6+5KE0Y/PSOI6xchOJE8SmD1H3a?= =?us-ascii?Q?8OFPRmvNN4DniLqnBKH/vMkD/7Lip5v0fbVCfR1LiCn70oOWcQ85CtYjkBnW?= =?us-ascii?Q?CvKE1Usw99jd5oVQawHk5YpZl3OhnzrYA/yx8yNNGy8oBqJjWXS3WJW6jdoy?= =?us-ascii?Q?sx9E950t57UzHungca/6geg/SqBbqwU7WHwqXXesjfuDftoR5/zhK62jSZ7Q?= =?us-ascii?Q?DP68m3jahc3CmVcAazJ64KNEOYRr1z3xRHA+E/tCb4w0mVavrNhqdpiLYj5S?= =?us-ascii?Q?awT87I2NbFF6pK/zSgPiSM+PgxArZt61iManPLjnfw5yEZbB5lDufyWlLhKn?= =?us-ascii?Q?yfI/remVDu9+wrZnT4UNor5BiDWPbZI9D29r5pNuqRuuRvjrl3arBfHDXC32?= =?us-ascii?Q?9cgEP93k01CMXdJczkbAbZDEugjBZrctMWAuDzvavJtv8XcnuvEXBVZDxTky?= =?us-ascii?Q?PPkDFQulgCKNxnII3djQera4cqbeQ5wY6pgKBSNpac3Et5vPFYyjnNZFBlXr?= =?us-ascii?Q?A/t63NhOVafOPKvQYMJWeopkJENivD+qMJfXeayijG/4H5Ax5bphGUao5WAo?= =?us-ascii?Q?EmY1PSN9zBV31LCSLuRMGr9pYL1x1yAb8mNaaZMbOQCHmGdgU3tQ66jmUf5u?= =?us-ascii?Q?ZSuGSwgH2CbB8uCcKh4rLBvtk6YZqWnqzFdxj11tv8itJ+P+fsvyd87hfv4X?= =?us-ascii?Q?fIY+F69GWjBHmMqB4gjEOQa2sra4ly1gpK80RjaN6RNtlHwlDlPTFWjbJXUb?= =?us-ascii?Q?ZkeiYBvn0z7IEABJJpboXHo/XRvmuQULahYL3Jpj?= X-MS-Exchange-CrossTenant-Network-Message-Id: 556543ec-e39e-4c41-3c46-08dcb7a62061 X-MS-Exchange-CrossTenant-AuthSource: DM4PR11MB6020.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Aug 2024 12:32:11.6832 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: ApkKzURpHm/TMu3rr850BAz388N4hQyvHG2X87n/fFfo8bof1wcgkOUu+lgSmJDaXT4PogndY/yJN5Zfnnuf6w== X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR11MB8336 X-OriginatorOrg: intel.com On 2024-08-08 at 12:22:07 +0200, Peter Zijlstra wrote: > On Thu, Aug 08, 2024 at 06:15:50PM +0800, Chen Yu wrote: > > Hi Peter, > > > > On 2024-07-27 at 12:27:53 +0200, Peter Zijlstra wrote: > > > Part of the reason to have shorter slices is to improve > > > responsiveness. Allow shorter slices to preempt longer slices on > > > wakeup. > > > > > > Task | Runtime ms | Switches | Avg delay ms | Max delay ms | Sum delay ms | > > > > > > 100ms massive_intr 500us cyclictest NO_PREEMPT_SHORT > > > > > > 1 massive_intr:(5) | 846018.956 ms | 779188 | avg: 0.273 ms | max: 58.337 ms | sum:212545.245 ms | > > > 2 massive_intr:(5) | 853450.693 ms | 792269 | avg: 0.275 ms | max: 71.193 ms | sum:218263.588 ms | > > > 3 massive_intr:(5) | 843888.920 ms | 771456 | avg: 0.277 ms | max: 92.405 ms | sum:213353.221 ms | > > > 1 chromium-browse:(8) | 53015.889 ms | 131766 | avg: 0.463 ms | max: 36.341 ms | sum:60959.230 ms | > > > 2 chromium-browse:(8) | 53864.088 ms | 136962 | avg: 0.480 ms | max: 27.091 ms | sum:65687.681 ms | > > > 3 chromium-browse:(9) | 53637.904 ms | 132637 | avg: 0.481 ms | max: 24.756 ms | sum:63781.673 ms | > > > 1 cyclictest:(5) | 12615.604 ms | 639689 | avg: 0.471 ms | max: 32.272 ms | sum:301351.094 ms | > > > 2 cyclictest:(5) | 12511.583 ms | 642578 | avg: 0.448 ms | max: 44.243 ms | sum:287632.830 ms | > > > 3 cyclictest:(5) | 12545.867 ms | 635953 | avg: 0.475 ms | max: 25.530 ms | sum:302374.658 ms | > > > > > > 100ms massive_intr 500us cyclictest PREEMPT_SHORT > > > > > > 1 massive_intr:(5) | 839843.919 ms | 837384 | avg: 0.264 ms | max: 74.366 ms | sum:221476.885 ms | > > > 2 massive_intr:(5) | 852449.913 ms | 845086 | avg: 0.252 ms | max: 68.162 ms | sum:212595.968 ms | > > > 3 massive_intr:(5) | 839180.725 ms | 836883 | avg: 0.266 ms | max: 69.742 ms | sum:222812.038 ms | > > > 1 chromium-browse:(11) | 54591.481 ms | 138388 | avg: 0.458 ms | max: 35.427 ms | sum:63401.508 ms | > > > 2 chromium-browse:(8) | 52034.541 ms | 132276 | avg: 0.436 ms | max: 31.826 ms | sum:57732.958 ms | > > > 3 chromium-browse:(8) | 55231.771 ms | 141892 | avg: 0.469 ms | max: 27.607 ms | sum:66538.697 ms | > > > 1 cyclictest:(5) | 13156.391 ms | 667412 | avg: 0.373 ms | max: 38.247 ms | sum:249174.502 ms | > > > 2 cyclictest:(5) | 12688.939 ms | 665144 | avg: 0.374 ms | max: 33.548 ms | sum:248509.392 ms | > > > 3 cyclictest:(5) | 13475.623 ms | 669110 | avg: 0.370 ms | max: 37.819 ms | sum:247673.390 ms | > > > > > > As per the numbers the, this makes cyclictest (short slice) it's > > > max-delay more consistent and consistency drops the sum-delay. The > > > trade-off is that the massive_intr (long slice) gets more context > > > switches and a slight increase in sum-delay. > > > > > > [mike: numbers] > > > Signed-off-by: Peter Zijlstra (Intel) > > > Tested-by: Mike Galbraith > > > > Besides this short preemption, it seems that an important patch is missing from > > this patch set, that was originally from Prateek and you refined it to fix the > > current task's false negative eligibility: > > https://lore.kernel.org/lkml/20240424150721.GQ30852@noisy.programming.kicks-ass.net/ > > > > The RESPECT_SLICE is introduced to honor the current task's slice during wakeup preemption. > > Without it we got reported that over-preemption and performance downgrading are observed > > when running SPECjbb on servers. > > So I *think* that running as SCHED_BATCH gets you exactly that > behaviour, no? SCHED_BATCH should work as it avoids the wakeup preemption as much as possible. Except that RESPECT_SLICE considers the cgroup hierarchical to check if the current sched_entity has used up its slice, which seems to be less aggressive. thanks, Chenyu