linux-kernel - Re: [PATCH v3 2/6] ANDROID: binder: add min sched

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Message-ID: <CAB0TPYFf3XaaxsnwaQ3CD-AWcyxkfDFwSQM7L6+1Bq2Q8i5NLg@mail.gmail.com>
Date:   Thu, 16 Nov 2017 10:27:48 +0100
From:   Martijn Coenen <maco@...roid.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        John Stultz <john.stultz@...aro.org>,
        Todd Kjos <tkjos@...gle.com>,
        Arve Hjønnevåg <arve@...roid.com>,
        Sherry Yang <sherryy@...roid.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Amit Pundir <amit.pundir@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>, devel@...verdev.osuosl.org,
        Martijn Coenen <maco@...gle.com>
Subject: Re: [PATCH v3 2/6] ANDROID: binder: add min sched_policy to node.

On Wed, Nov 15, 2017 at 2:02 PM, Peter Zijlstra <peterz@...radead.org> wrote:
>> Internally, we use the priority map that the kernel
>> uses, e.g. [0..99] for real-time policies and [100..139]
>> for the SCHED_NORMAL/SCHED_BATCH policies.
>
> I will break that without consideration if I have to. That really isn't
> something anybody outside of the core code should rely on.

I mostly used these because it makes it easier to debug, since that
range is used in other places in the kernel (and in trace events). All
priority calculations use things that are in sched headers, like
NICE_TO_PRIO, PRIO_TO_NICE, and MAX_USER_RT_PRIO. So things wouldn't
necessarily break if you just changed the value ranges. If you
inverted the range, that would be a problem...