From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) (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 C36022356BA for ; Fri, 23 Jan 2026 20:04:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.11 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769198669; cv=none; b=Ic9wFxGUdppKL9TExKX7rrZY5Oy0oGifz5tSunlkgqGTBMt/pibcxxh3nOYqE0t33EFmB4mePO2oOQEm5RDZYex+LDzgzTG0HwOU9XxBXaka3xIE66G57r/yhoTYvnG2qoK7yOJ4o7TwduZMLs5OxVrWaUz8CuYE9iSmPiO8R64= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769198669; c=relaxed/simple; bh=jqNc3QCmpXqnCw3FXoFUjYdxUWtYOjx3k6AoDOsVTLA=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=Fs0SXq/t+zU54GtMo0kSFqhc66gOurWt33CYyKgw0RjkZgPRhYe1QqFacyNGn0OF2uOqIEZRZCgbauHnfryR4w7f8ZXpVPnJDVSRVUFpKrHvJk3dTS1bYRxIX03iUckXN/LBH4pCPNEm/P/E4Gw9G7HOCrB7fiS9dUrFprQ5QDU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 241CCC23E5; Fri, 23 Jan 2026 20:04:25 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf08.hostedemail.com (Postfix) with ESMTPA id 0671620027; Fri, 23 Jan 2026 20:04:21 +0000 (UTC) Date: Fri, 23 Jan 2026 15:04:50 -0500 From: Steven Rostedt To: Juri Lelli Cc: Peter Zijlstra , tglx@linutronix.de, arnd@arndb.de, anna-maria@linutronix.de, frederic@kernel.org, luto@kernel.org, mingo@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-kernel@vger.kernel.org, oliver.sang@intel.com Subject: Re: [PATCH v2 3/6] hrtimer,sched: Add fuzzy hrtimer mode for HRTICK Message-ID: <20260123150428.25972f96@gandalf.local.home> In-Reply-To: References: <20260121162010.647043073@infradead.org> <20260121162507.757183816@infradead.org> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) 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-Transfer-Encoding: 7bit X-Rspamd-Server: rspamout07 X-Rspamd-Queue-Id: 0671620027 X-Stat-Signature: wn67c4uqo1ij4daitbnckw6acw9n9gd1 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1+/0Tmd741yaJI6qeA/3uiP3jEMpcGZ3p4= X-HE-Tag: 1769198661-154064 X-HE-Meta: U2FsdGVkX18HTizGwuxurmnaf9+/XzuRi0WXkzupyu/i/2BFTij0x0utjHrB+STTjMI0+0rVpl7ev2ZIbM050MCvPXULXNOx9rrygJ6MnEFY6DLgUxQTr1QJZyYSf6UBp6GTOkqV2QWCQK54/Jktqwcr7xM3SUfEt12vjfm6MOOr3weKnyVFWHrEpndPedz0yWklHRXdKvqi/B5FEBjJfR+FwE8rWo71WGgQbhjtuaF1oOzwq8cBktmt2QiPbvzIV2HPZw/9d62Kj2eizG2luF8y8OsTC/hyftpuGSCKFlT8ZugeFUT/eUhzPOfZzLq7Eo7Waj1A/kAWuv0t5Hejrd65GO5BFDg+ On Thu, 22 Jan 2026 14:12:28 +0100 Juri Lelli wrote: > Hello, > > On 21/01/26 17:20, Peter Zijlstra wrote: > > Upon schedule() HRTICK will cancel the current timer, pick the next > > task and reprogram the timer. When schedule() consistently triggers > > due to blocking conditions instead of the timer, this leads to endless > > reprogramming without ever firing. > > > > Mitigate this with a new hrtimer mode: fuzzy (not really happy with > > that name); this mode does two things: > > Does the more common (lazier :) 'lazy' work better? I don't like either fuzzy or lazy. Fuzzy makes me think of just random entries (for fuzz testing and such). Lazy is to postpone things to do things less often. What about "speculative"? Like branch prediction and such. Where a timer is expected to be used at a certain time but it may not be? -- Steve