linux-kernel - Re: sched: Move SCHED

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Message-Id: <20210427145925.5246-1-borntraeger@de.ibm.com>
Date:   Tue, 27 Apr 2021 16:59:25 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     peterz@...radead.org
Cc:     bristot@...hat.com, bsegall@...gle.com, dietmar.eggemann@....com,
        greg@...ah.com, gregkh@...uxfoundation.org, joshdon@...gle.com,
        juri.lelli@...hat.com, linux-kernel@...r.kernel.org,
        linux@...musvillemoes.dk, mgorman@...e.de, mingo@...nel.org,
        rostedt@...dmis.org, valentin.schneider@....com,
        vincent.guittot@...aro.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, borntraeger@...ibm.com
Subject: Re: sched: Move SCHED_DEBUG sysctl to debugfs

Peter,

I just realized that we moved away sysctl tunabled to debugfs in next.
We have seen several cases where it was benefitial to set
sched_migration_cost_ns to a lower value. For example with KVM I can
easily get 50% more transactions with 50000 instead of 500000. 
Until now it was possible to use tuned or /etc/sysctl.conf to set
these things permanently. 

Given that some people do not want to have debugfs mounted all the time
I would consider this a regression. The sysctl tunable was always 
available.

I am ok with the "informational" things being in debugfs, but not
the tunables. So how do we proceed here?

Christian