From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 3A9EA3B19A8; Wed, 13 May 2026 19:26:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778700385; cv=none; b=ZzWBIARd3IGxxS9NfeXVEcrIMXhlZsI9P0YUoL1EE7acZ801UXkjqyimxZ0sf/tvAbXKoO0VQHtlOWPYlvOApV35l+xXmYtvAESosp4UHgInnhfhx/LjjPHwwaO0BKKCSqHppjjj2MsUw2AWWHeWbywDw/lRRRMPrghi6QP79BI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778700385; c=relaxed/simple; bh=45c9OV2GPaYfwize4vc5GxTCEBADyTVSFmlnujT5NMk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lM7o1BRFTUox0FAGVdMHaKQIpHReTn+cGWw76cSQHQMq80LBy0cCrVUfn3gnBJ5YCfz8HFY+42dTK0R6sGANtxx7wrf13n3zuY1RU0XY2bJNsyp6mCrW1gW/W66Lxy/i1slnNk/Y8hcc4bMF2rdgErV6GqCz2Uoln+b8sAiCnG8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=HJfkqXV+; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="HJfkqXV+" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=5jXgOm2W/v1Vl1bT+RF7zk/Xq/msqAlwEyLXpPVPOgA=; b=HJfkqXV+o9pZuHWl156uv9ZV1+ pAU2fPeisDFyWOFbut8ow8ktjj2bC4mXW5tWR+lScGE4ycAW6WnbitCChoduuN8LwzsBfUbDl5BmP xNdaqsf20yeJuhpMBbzq2iMviJaFhZVTbHMaR1plTPwOBP1MwX60viyi+7jsK35C5KXa6K4hktEVX iMOqPFzM+nEy/L+epKsE8B9XQ/5fOffw66BfqUQEvXN4YvlywwsuficHa+2WKTXnd5TqL3mT5mKtV +tdwDCAUbR8KJ1Gd7i/flhb1qvyv1NeielP4naekfJ1Inewrcigqg8s4qjK7BJ25kK6KNmpCg319C D6FKTjZw==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wNFDa-000000018qi-2vA8; Wed, 13 May 2026 19:26:07 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 026183007A4; Wed, 13 May 2026 21:26:05 +0200 (CEST) Date: Wed, 13 May 2026 21:26:05 +0200 From: Peter Zijlstra To: Dmitry Ilvokhin Cc: Ingo Molnar , Will Deacon , Boqun Feng , Waiman Long , Thomas Bogendoerfer , Juergen Gross , Ajay Kaher , Alexey Makhalov , Broadcom internal kernel review list , Thomas Gleixner , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Arnd Bergmann , Dennis Zhou , Tejun Heo , Christoph Lameter , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, virtualization@lists.linux.dev, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH v6 0/7] locking: contended_release tracepoint instrumentation Message-ID: <20260513192605.GA2545104@noisy.programming.kicks-ass.net> References: Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, May 05, 2026 at 05:09:29PM +0000, Dmitry Ilvokhin wrote: > This series adds a contended_release tracepoint that fires on the > holder side when a lock with waiters is released. This provides: > > - Hold time estimation: when the holder's own acquisition was > contended, its contention_end (acquisition) and contended_release > can be correlated to measure how long the lock was held under > contention. > > - The holder's stack at release time, which may differ from what perf lock > contention --lock-owner captures if the holder does significant work between > the waiter's arrival and the unlock. > > Note: for reader/writer locks, the tracepoint fires for every reader > releasing while a writer is waiting, not only for the last reader. And for qspinlock. I am really not sure this is worth the overhead for qspinlock / rwlock.