Messages in this thread | | | Date | Wed, 8 Nov 2023 14:58:12 +0100 | Subject | Re: [PATCH v5 6/7] sched/deadline: Deferrable dl server | From | Daniel Bristot de Oliveira <> |
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On 11/8/23 13:44, Peter Zijlstra wrote: > Should we rather not cap the runtime, something like so? > > Because the above also causes period drift, which we do not want.
like in the example I showed before:
- 3/10 reservation (30%). - w=waiting - r=running - s=sleeping - T=throttled - fair server dispatched at 0, starvation from RT.
|wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww|rrrrrrrrrrrrrrrrrrrrrrrrrrrrrr|TTTTTTTTTT[...]TTTTTTTTTTT|rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr|TTTTTTT |___________________________period 1_________________________________|_________period 2________________________[...]___________|___period 3____________________|[.... internal-period 0---------1---------2---------3---------4---------5---------6--------7--------8---------9----------10.......11.[...]16.........17........18........19........20|[.... < Real-time ---------------------------------------------------------------------+---------------------------------------------------------| | +new period
From "real-world/wall clock" the internal period shift produces the "zerolax" timeline. It runs 3 units of time before the 10's.
If one has a mix of DL and FIFO task, and want to enforce a given response time to the fair server, they can reduce the fair server period to achieve that.
-- Daniel
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