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Tue, 04 Nov 2025 05:45:59 -0800 (PST) Received: from vschneid-thinkpadt14sgen2i.remote.csb ([2a01:e0a:36d:2b80:e937:44f0:a96a:94f2]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-429dc1a8528sm4959089f8f.21.2025.11.04.05.45.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Nov 2025 05:45:58 -0800 (PST) From: Valentin Schneider To: Shrikanth Hegde Cc: Nicolas Saenz Julienne , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Arnaldo Carvalho de Melo , Josh Poimboeuf , Paolo Bonzini , Arnd Bergmann , Frederic Weisbecker , "Paul E. McKenney" , Jason Baron , Steven Rostedt , Ard Biesheuvel , Sami Tolvanen , "David S. Miller" , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Mel Gorman , Andrew Morton , Masahiro Yamada , Han Shen , Rik van Riel , Jann Horn , Dan Carpenter , Oleg Nesterov , Juri Lelli , Clark Williams , Yair Podemsky , Marcelo Tosatti , Daniel Wagner , Petr Tesarik , linux-kernel@vger.kernel.org, linux-mm@kvack.org, rcu@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH v6 23/29] context-tracking: Introduce work deferral infrastructure In-Reply-To: References: <20251010153839.151763-1-vschneid@redhat.com> <20251010153839.151763-24-vschneid@redhat.com> Date: Tue, 04 Nov 2025 14:45:56 +0100 Message-ID: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: uu_k1lsp1Kyjzce0qm7_4Bgore2RIYnf7_SgoWi21Ps_1762263960 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: D07A580017 X-Stat-Signature: fzd8915678s373jbdc3dbm9grbioh3m4 X-HE-Tag: 1762263962-968243 X-HE-Meta: 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 B1KSpaGV aZgnG1cm93e5M+5j9t+AeHzdQG8ilEgc8YMSPl/FFs97hmZr/8xkUEBhcB9dPuPxoDbEIY7UVT4EA7RO/LNen4qo4wqo7igrohLqjPdOt7eLHc3yai1G+3IiRNsJQDUY/EZFs6ynt86M0s6USC4L1SCsnA9MEK6ih6uLqZmHjx2Ev/9xnloUAyEhWrP7wgqw7y8GCyiu+nOYnZvNcGSXnTd6A8TvujnEM0gvMtWs4u8g9zH8ykYhgTEJLCoSdbx2CXELzgVqkyekOl3IesbBiznrJrmGeQFLcUG7N76LK/YL1x3MzadVKV6DiobN75U4OAwpo8Qh8hCq7QJ7LfUoosDk1uTIgWOib823WEP9cOMJUY2ZlzblHiw4a/MSTT6vHeXj4gRkTGg5YQI5rBywUbyAX5EecxYp37CAhceyyayynFUM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 03/11/25 14:02, Shrikanth Hegde wrote: > Hi Valentin. > > On 10/10/25 9:08 PM, Valentin Schneider wrote: >> +++ b/include/linux/context_tracking_work.h >> @@ -0,0 +1,26 @@ >> +/* SPDX-License-Identifier: GPL-2.0 */ >> +#ifndef _LINUX_CONTEXT_TRACKING_WORK_H >> +#define _LINUX_CONTEXT_TRACKING_WORK_H >> + >> +#include >> + >> +enum { >> + CT_WORK_n_OFFSET, >> + CT_WORK_MAX_OFFSET >> +}; >> + >> +enum ct_work { >> + CT_WORK_n = BIT(CT_WORK_n_OFFSET), >> + CT_WORK_MAX = BIT(CT_WORK_MAX_OFFSET) >> +}; >> + >> +#include >> + > > It fails to compile on powerpc (likey any arch other than x86) > Woops, thanks for testing! > In file included from ./include/linux/context_tracking_state.h:8, > from ./include/linux/hardirq.h:5, > from ./include/linux/interrupt.h:11, > from ./include/linux/kernel_stat.h:8, > from ./include/linux/cgroup.h:27, > from ./include/linux/memcontrol.h:13, > from ./include/linux/swap.h:9, > from ./include/linux/suspend.h:5, > from arch/powerpc/kernel/asm-offsets.c:21: > ./include/linux/context_tracking_work.h:17:10: fatal error: > asm/context_tracking_work.h: No such file or directory > 17 | #include > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > Gating works for compile, but no benefit of the series. > > +#ifdef HAVE_CONTEXT_TRACKING_WORK > #include > +#endif > Huh, looking at this I wonder why I shoved that here. That include belongs in context_tracking.c itself; I'll fix that. > > I have been trying to debug/understand the issue seen with isolcpus= and > nohz_full=. system is idle, even then it occasionally woken up to do > some work. So I was interesting if this series can help. Is there some ongoing thread for this particular issue or is this just something you're experimenting with? If you suspect stray IPIs hitting isolated CPUs I'd recommend tracing with these events enabled: ipi_send_cpu ipi_send_cpumask