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Avila" Subject: Re: [PATCH RFC v4 2/3] sched: Avoid placing RT threads on cores handling long softirqs Message-ID: References: <20221003232033.3404802-1-jstultz@google.com> <20221003232033.3404802-3-jstultz@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: nKJVCwofD17k3BUzqOOe-C-aWODyeKIm X-Proofpoint-GUID: e2PCv9anuV48p5jqlTX0k-a6iHr73z1j X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2022-10-21_04,2022-10-21_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 mlxlogscore=840 lowpriorityscore=0 malwarescore=0 mlxscore=0 priorityscore=1501 phishscore=0 clxscore=1011 bulkscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2209130000 definitions=main-2210230047 X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_EF,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Oct 22, 2022 at 06:34:37PM +0000, Joel Fernandes wrote: > > In my reading of your approach if you find a way to additionally > > indicate long softirqs being handled by the remote ksoftirqd, it > > would cover all obvious/not-corner cases. > > How will that help? The long softirq executing inside ksoftirqd will disable > preemption and prevent any RT task from executing. Right. So the check to deem a remote CPU unfit would (logically) look like this: (active | pending | ksoftirqd) & LONG_SOFTIRQ_MASK > Did I miss something? Or me :) > thanks, > > - Joel >