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Wed, 16 Jul 2025 07:38:39 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFptKKgabK4YSBzr4A23TCNpKLWSztNfIHJhjjgHgXZXCD1z41s30Edp5+SqPDwLIWCpRXH1g== X-Received: by 2002:a5d:5f50:0:b0:3a4:d53d:be20 with SMTP id ffacd0b85a97d-3b60dd54803mr2670833f8f.18.1752676718428; Wed, 16 Jul 2025 07:38:38 -0700 (PDT) Received: from gmonaco-thinkpadt14gen3.rmtit.csb ([185.107.56.42]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b5f16a6016sm16163068f8f.69.2025.07.16.07.38.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Jul 2025 07:38:38 -0700 (PDT) Message-ID: Subject: Re: [PATCH v3 12/17] sched: Adapt sched tracepoints for RV task model From: Gabriele Monaco To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Steven Rostedt , Masami Hiramatsu , linux-trace-kernel@vger.kernel.org, Nam Cao , Tomas Glozar , Juri Lelli , Clark Williams , John Kacur Date: Wed, 16 Jul 2025 16:38:36 +0200 In-Reply-To: <20250716141958.GC905792@noisy.programming.kicks-ass.net> References: <20250715071434.22508-1-gmonaco@redhat.com> <20250715071434.22508-13-gmonaco@redhat.com> <20250716123832.GW1613200@noisy.programming.kicks-ass.net> <122cfd4ba6b0805e91ff09526d5d159ff3871964.camel@redhat.com> <20250716134513.GB905792@noisy.programming.kicks-ass.net> <20250716141958.GC905792@noisy.programming.kicks-ass.net> Autocrypt: addr=gmonaco@redhat.com; prefer-encrypt=mutual; keydata=mDMEZuK5YxYJKwYBBAHaRw8BAQdAmJ3dM9Sz6/Hodu33Qrf8QH2bNeNbOikqYtxWFLVm0 1a0JEdhYnJpZWxlIE1vbmFjbyA8Z21vbmFjb0ByZWRoYXQuY29tPoiZBBMWCgBBFiEEysoR+AuB3R Zwp6j270psSVh4TfIFAmbiuWMCGwMFCQWjmoAFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgk Q70psSVh4TfJzZgD/TXjnqCyqaZH/Y2w+YVbvm93WX2eqBqiVZ6VEjTuGNs8A/iPrKbzdWC7AicnK xyhmqeUWOzFx5P43S1E1dhsrLWgP Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-1.fc42) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2025-07-16 at 16:19 +0200, Peter Zijlstra wrote: > So in general I'm a minimalist; less is more etc. > > Even if you care about latencies, I don't see what that tracepoint adds. = In > fact, I don't even see the point of the .is_switch argument to > trace_sched_exit_tp(). That state can be fully reconstructed from having = seen > trace_sched_switch() between trace_sched_{enter,exit}_tp(). > > As for the IRQ state, if you see: > > =C2=A0trace_sched_enter_tp(); > =C2=A0trace_irq_disable(); > =C2=A0trace_irq_enable(); > > You already know all you need to know; there was no switch, otherwise > it would'be been: > > =C2=A0trace_sched_enter_tp(); > =C2=A0trace_irq_disable(); > =C2=A0trace_sched_switch(); > =C2=A0trace_irq_enable(); > Or you could see: trace_sched_enter_tp(); trace_irq_disable(); trace_irq_enable(); trace_irq_disable(); trace_sched_switch(); trace_irq_enable(); Where in fact there /was/ a switch, that trace was actually something like: trace_sched_enter_tp(); trace_irq_disable(); **irq_entry();** **irq_exit();** trace_irq_enable(); trace_irq_disable(); trace_sched_switch(); trace_irq_enable(); So as you said, we can still reconstruct what happened from the trace, but = the model suddenly needs more states and more events. If we could directly tell whether interrupts were disabled manually or from= an actual interrupt, that wouldn't be necessary, for instance (as in the origi= nal model by Daniel). I get your point why we don't really need the additional tracepoint, but so= me arguments giving more context come almost for free. > Also, can we get rid of that CALLER_ADDR0 argument as well? Yeah good point, this might have been be useful to understand some things (__schedule called from preempt_irq for instance) but it's a pain to make s= ense out of it.