linux-kernel - Re: [PATCH 0/5] BT scheduling class

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Message-ID: <20190621123625.GJ3436@hirez.programming.kicks-ass.net>
Date:   Fri, 21 Jun 2019 14:36:25 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     xiaoggchen@...cent.com
Cc:     jasperwang@...cent.com, heddchen@...cent.com, mingo@...hat.com,
        linux-kernel@...r.kernel.org, tj@...nel.org, lizefan@...wei.com,
        hannes@...xchg.org, cgroups@...r.kernel.org
Subject: Re: [PATCH 0/5] BT scheduling class

On Fri, Jun 21, 2019 at 03:45:52PM +0800, xiaoggchen@...cent.com wrote:
> From: chen xiaoguang <xiaoggchen@...cent.com>
> 
> This patch set introduces a new scheduler, we name it BT scheduler
> for the moment.

> The BT scheduler is similar with the CFS scheduler. We also use the
> rb-tree as the run queue to save the runnable tasks. And the vruntime 
> concept is also used in the BT scheduler. And the priority of BT scheduler
> is from 140 to 179. So now the schedulers in the kernel are as follows:
> deadline, RT, CFS, BT and idle.

NAK; it has no forward progress guarantees. This is also the reason why
SCHED_IDLE is not a true idle time scheduler but a very low weight CFS
tasks.

It also has some very 'interesting' starvation cases, consider one of
your BT tasks owns a mutex, but then there are there are runnable CFS
tasks. The BT task will never get runtime and release the mutex.

Also; NAK at all the duplication.