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Wysocki" , Daniel Lezcano , Anna-Maria Behnsen , Frederic Weisbecker , Ingo Molnar , Thomas Gleixner , Ilya Leoshkevich , Christian Borntraeger , linux-s390 , linux-kernel Subject: Re: [PATCH 1/5] s390/tick: Remove CIF_NOHZ_DELAY flag Message-ID: <20260609103904.9217Afa-hca@linux.ibm.com> References: <20260609075213.31094-1-meted@linux.ibm.com> <20260609075213.31094-2-meted@linux.ibm.com> <7d2ace86-f355-4ff7-886b-7963574b2202@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=b4uCJNGx c=1 sm=1 tr=0 ts=6a27ed4f cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=kj9zAlcOel0A:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=8kDfDS3PkAXohz4YEQsA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-ORIG-GUID: QQVKhxUyD4uxvOfnfSqUDHAMUpOs-KnI X-Proofpoint-GUID: QQVKhxUyD4uxvOfnfSqUDHAMUpOs-KnI X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjA5MDA5OSBTYWx0ZWRfX/zDG9PyFBniz gnzJ8xP2ouoGYNlThSkuxN9Y/qDd3X2N2IZwuZ6dukD4udZhs5yQHwEqTNDy2X177L/44waTgRs fCkWVUfCfUti4cPY0BEDdPNMDJmI3AxbZYcSjL0KgTGqA48Vqu5Db68BdwBCn/KQg7yiWDpUT4f PW4+RiJNTdsbDX/hq6ouGAoSJXcsB6Z4Ugd8kZfNh693WQMcFxbdl8/dEOktvbqzNSEYedCICw2 Rc9WHHyDcyGq/m4rv2pf/JJm21UJ/Begvo08/XcnCy7SO4vXEu2xCcIE5AZ/+R/rX50lRxkSMMl 4lUc/q0e5GdSKlDEKCpRWqDe6go0sFmusVh/+vmjnulZiHg4ryuqZHrc1RhSnqW6GNgqCliG0EC tme/6BbAszqzgVtxV6949mjKegJvRqhJzHXzVLcaOqpXgDHABlcB9G9kAPxObuHu37yBAQ3znqp tHGDHohkWlPhUcX+7Ew== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-09_02,2026-06-09_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 spamscore=0 bulkscore=0 phishscore=0 priorityscore=1501 lowpriorityscore=0 adultscore=0 malwarescore=0 impostorscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606090099 On Tue, Jun 09, 2026 at 12:04:08PM +0200, Mete Durlu wrote: > On 6/9/26 11:52, Christian Loehle wrote: > > > > > Remove obsolete tick delay heuristic [1]. The upcoming cpuidle driver > > > > > handles frequent sleep/wakeup cycles more effectively. > > > > > > > > > > [1] https://lore.kernel.org/all/20090929122533.402715150@de.ibm.com/ > > > > > > > > > > Suggested-by: Heiko Carstens > > > > > Signed-off-by: Mete Durlu > > > > > --- > > > > For bisectibility does it make sense to move this and 2/5 to the end? > > > > > > I am unable to see how that would help. Could you elaborate? > > > > CIF_NOHZ_DELAY is only obsolete because of the new s390 cpuidle driver > > handles NOHZ better overall right? > > So my suggestion was to only obsolete it once everything is in place? > > CIF_NOHZ_DELAY could modify the idle driver's decisions when it comes to > disabling the scheduling tick. It could be hard to bisect a problem with > the driver if we move the removal of the flag after the drivers > introduction. Because then the commit that enables the driver can have > a significantly different behavior. > > Plus,having the flag obsolete without any other mechanism doing a > similar job would make the effect and related behavior more visible and > easier to debug. The flag is questionable since a long time. So I wouldn't focus on the question if the removal comes at the beginning or end of this series. I'm more than happy to see it go.