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Hi Luca,

On Thu, May 11, 2023 at 3:37 AM luca abeni <luca.abeni@xxxxxxxxxxxxxxx> wrote:

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I am sorry I missed sending more details before sending out v2. So, I

think there is another bug in the existing implementation. Let me try

to explain the details.

SMP GRUB paper has the equation for depreciating runtime as:

dq_i = -max{u_i, 1 - (extra_bw + Uinact)} dt

Since we are caping at Umax, the equation would be

dq_i = -(max{u_i, Umax - (extra_bw + Uinact)} / Umax) dt (1)

But existing implementation is:

dq_i = -max{u_i/Umax, 1 - (extra_bw + Uinact)} dt (2)

Here in (2), we factored Umax only to the first term "u_i" and the

second term in max{} was as left as it is. What do you think?

Now with normal DL and SCHED_FLAG_RECLAIM tasks, equation (1) can be

re-written as:

dq_i =

-(max{u_i, Ureclaim_max - (extra_bw + Uinact)}/Ureclaim_max)dt (3)

I tested this equation (3) and it works as expected. What do you think

about the correctness of equation (3)?

I felt that, since we are using sequential reclaim mentioned in the

paper and we isolate all parameters per-cpu(except for extra_bw) we

could use the "-dq = -(U/Umax) dt" equation as it was simpler than

equation (3). Sorry that I missed discussing this. I shall send out

v3 with equation (3), if you think it's the right way to go to enforce

deadline guarantees.

Thanks,

Vineeth

**Next message:**Dmitry Torokhov: "Re: [RESEND PATCH] dt-bindings: input: cypress,cyapa: convert to dtschema"**Previous message:**Andreas Schwab: "Re: [PATCH v8 1/3] riscv: Introduce CONFIG_RELOCATABLE"**In reply to:**luca abeni: "Re: [PATCH 1/2] sched/deadline: accurate reclaim bandwidth for GRUB"**Next in thread:**luca abeni: "Re: [PATCH 1/2] sched/deadline: accurate reclaim bandwidth for GRUB"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]