From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 943661FC3; Thu, 24 Jul 2025 05:31:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753335062; cv=none; b=DNZULkMLNU/eAL2fB6ylDyyEeAg5qeijuOzJvgwtsrsldY8BUFLtG+90SEyYcEgiIkp2bxnxQbBRDBPtQ0udvZ3RBEBUzReB3KUVtteElzdGhZbYBJXohcf96/1rvdZm941eUXvwRNQgJWH/etGYjXjlpReyqz19fm9fuZPvSss= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753335062; c=relaxed/simple; bh=Ibk2qzQoxKWdDn9Ul5l5A4RYbVwHkJe/LQQ5SUv28oo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Y3bXBw7UMFzoNxERPVbym3Ro3QsjUOnaLVk4cavQb3vhyFS+Z6TkroY4pwoB1i2syWh985+5/RX6e0l71ga1ipThRtzNs5oWU/eJ/ADeS9qvcTcGZ1g/X3q2WhG9ozgeT+ropfP+x3kfqTA1sVn8KOX7gf6L2zyEwrgUA8xnCVQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OqiaoEUF; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OqiaoEUF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6CF5FC4CEED; Thu, 24 Jul 2025 05:30:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1753335062; bh=Ibk2qzQoxKWdDn9Ul5l5A4RYbVwHkJe/LQQ5SUv28oo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=OqiaoEUF/cqAb3LHoNSvU1pG0B4FUddn1UrGl7nEhGovP4r6rzsChYdS/geS2HsLQ 4EAV6yYfm+hzScH5UCgAe8GYyvOx1zWVYpv1LmA9ns/nPT7wjr9rGpRIWw67MT7wZb rvxqvjpg7O1c6hckK3Q7R9UO1Iill8Djk9sJ8ViTkA0yfsjT4pUcaEDn/NDEre1x3l TuQxToJ5reDVfW7Kc6MhdqIU4zW2QM8ITxjOqEe1CnRDmcG92CLhKZ0ET5uz6oMNfK Z6Ug67TeZYQ77IJHZcMF6E/l7mXec440yLap5OtlfPO1Ggoc9teOc9j7BuIawGMl0z /YYU6K7V7/oEQ== Message-ID: Date: Thu, 24 Jul 2025 07:30:57 +0200 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] genirq: add support for warning on long-running IRQ handlers To: Wladislav Wiebe , tglx@linutronix.de, corbet@lwn.net Cc: akpm@linux-foundation.org, paulmck@kernel.org, rostedt@goodmis.org, Neeraj.Upadhyay@amd.com, david@redhat.com, bp@alien8.de, arnd@arndb.de, fvdl@google.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, peterz@infradead.org References: <20250723182836.1177-1-wladislav.wiebe@nokia.com> Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 24. 07. 25, 7:18, Jiri Slaby wrote: > On 23. 07. 25, 20:28, Wladislav Wiebe wrote: >> Introduce a mechanism to detect and warn about prolonged IRQ handlers. >> With a new command-line parameter (irqhandler.duration_warn_us=), >> users can configure the duration threshold in microseconds when a warning >> in such format should be emitted: >> >> "[CPU14] long duration of IRQ[159:bad_irq_handler [long_irq]], took: >> 1330 us" >> >> The implementation uses local_clock() to measure the execution >> duration of the >> generic IRQ per-CPU event handler. > ...> +static inline void irqhandler_duration_check(u64 ts_start, > unsigned int irq, >> +                         const struct irqaction *action) >> +{ >> +    /* Approx. conversion to microseconds */ >> +    u64 delta_us = (local_clock() - ts_start) >> 10; > > Is this a microoptimization -- have you measured what speedup does it > bring? IOW is it worth it instead of cleaner "/ NSEC_PER_USEC"? > > Or instead, you could store the diff in irqhandler_duration_threshold_ns > (mind that "_ns") and avoid the shift and div completely. > > And what about the wrap? Don't you need abs_diff()? Not that ^^^, it won't work, but something else. But if I am counting correctly, the wrap is in 584 years if counted from 0. Well, for native/tsc, "Intel guarantees that the time-stamp counter will not wraparound within 10 years after being reset". I have no idea what virtualizations return to local_clock(). This is not my call to decide, though. > thanks, -- js suse labs