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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Jan 2026 06:31:24.6092 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 237ac9ff-137a-48de-e53b-08de526d5fdd X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN3PEPF0000B06A.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS4PR12MB999100 Hello Ryan, On 1/12/2026 2:22 PM, Ryan Roberts wrote: > On 12/01/2026 07:47, Peter Zijlstra wrote: >> On Fri, Jan 09, 2026 at 10:15:46AM +0000, Ryan Roberts wrote: >> >>> Here are the updated results, now including column for "revert #1 & #2". >>> >>> 6-18-0 (base) (baseline) >>> 6-19-0-rc1 (New NEXT_BUDDY implementation enabled) >>> revert #1 & #2 (NEXT_BUDDY disabled) >>> revert #2 (Old NEXT_BUDDY implementation enabled) >>> >>> >>> The regressions that are fixed by "revert #2" (as originally reported) are still >>> fixed in "revert #1 & #2". Interestingly, performance actually improves further >>> for the latter in the multi-node mysql benchmark (which is our VIP workload). >>> There are a couple of hackbench cases (sockets with high thread counts) that >>> showed an improvement with "revert #2" but which is gone with "revert #1 & #2". >>> >>> Let me know if I can usefully do anything else. >> >> If its not too much bother, could you run 6.19-rc with SCHED_BATCH ? The >> defining characteristic of BATCH is that it fully ignores wakeup >> preemption. > > Is there a way I can force all future tasks to use SCHED_BATCH at the system > level? One shortcut is to echo "NO_WAKEUP_PREEMPTION" into /sys/kernel/debug/sched/features but note it'll disable wakeup preemption for all tasks, including kthreads, which might adversely affect performance and is not an exact equivalent to only running the workload under SCHED_BATCH. For repro-collection/mysql-workload, (which I presume is [1]), there is a "WORKLOAD_SCHED_POLICY" environment variable that can be overridden [2] which controls the "CPUSchedulingPolicy" of the mysqld service. [1] https://github.com/aws/repro-collection/tree/main/workloads/mysql [2] https://github.com/aws/repro-collection/blob/a2cdf0455bd3422c9c1fc689ceac32971223b984/repros/repro-mysql-EEVDF-regression/main.sh#L102 -- Thanks and Regards, Prateek