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Tue, 27 Apr 2021 15:17:10 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5584BAE045; Tue, 27 Apr 2021 15:17:09 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.171.69.120]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 27 Apr 2021 15:17:09 +0000 (GMT) Subject: Re: sched: Move SCHED_DEBUG sysctl to debugfs To: Steven Rostedt Cc: peterz@infradead.org, bristot@redhat.com, bsegall@google.com, dietmar.eggemann@arm.com, greg@kroah.com, gregkh@linuxfoundation.org, joshdon@google.com, juri.lelli@redhat.com, linux-kernel@vger.kernel.org, linux@rasmusvillemoes.dk, mgorman@suse.de, mingo@kernel.org, valentin.schneider@arm.com, vincent.guittot@linaro.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org References: <20210412102001.287610138@infradead.org> <20210427145925.5246-1-borntraeger@de.ibm.com> <20210427110926.24f41fbb@gandalf.local.home> From: Christian Borntraeger Message-ID: Date: Tue, 27 Apr 2021 17:17:09 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: <20210427110926.24f41fbb@gandalf.local.home> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 8LnwMr35GvdP4-iKrSuyQ1vsFGyXLnDn X-Proofpoint-GUID: 8p0vcg5TR-O8GTMPBnw3xzhxG9KNmE4H X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-04-27_08:2021-04-27,2021-04-27 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 clxscore=1015 mlxscore=0 impostorscore=0 suspectscore=0 phishscore=0 lowpriorityscore=0 spamscore=0 mlxlogscore=999 bulkscore=0 adultscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104270107 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27.04.21 17:09, Steven Rostedt wrote: > On Tue, 27 Apr 2021 16:59:25 +0200 > Christian Borntraeger wrote: > >> 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? > > Should there be a schedfs created? > > This is the reason I created the tracefs file system, was to get the > tracing code out of debugfs, as debugfs is a catch all for everything and > can lead to poor and insecure interfaces that people do not want to add on > systems that they still want tracing on. > > Or perhaps we should add a "tunefs" for tunables that are stable interfaces > that should not be in /proc but also not in debugfs. Yes, a tunefs or schedfs could be considered a replacement for sysctl. It will still break existing setups with kernel.sched* things in /etc/sysctl.conf but at least there is a stable transition path.