From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 430B63644C3 for ; Tue, 14 Jul 2026 10:12:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784023974; cv=none; b=StcJP3bie1cXdrP8Kf7AvtBTaTxr3xcIGQhHWFhM19vro7jDIuYWdVXUo5Ou+n0BK3CTCUIBBiRvDiyGg2+uR1cIUQtCfXQ0aHJ7NJhcjckpR+IjwvNvLXtECtsTgtFc+cRrM6FTQYfUAYusxG5JL4QtcxLXM1h9Am8tIeqxXqo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784023974; c=relaxed/simple; bh=eGQhjevRi4VUY0qp+zJAH8KVskQKAiTQMslzprRoCd4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=srvFq2DYjTVSd0EWYkOmqD/GN+ZYhr6CEeBaDaY1mOdNkNLg93oqT2ie+4v4gYvbTPwd74vxLloy85kKrbJ2+MnhDjnfu7gAwCEBJM7N6B/Ler8GkKxqDqwg8X4YtdUTATOtIILnzNsc7baMnYvN8oBmEVL14MK8yWpQjD6hcTA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=zk2GyPuL; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=UX4RPTay; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="zk2GyPuL"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="UX4RPTay" Date: Tue, 14 Jul 2026 12:12:48 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1784023971; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=iTkmerU8UE91t1uqi1Zg80dTpHp+N6TCCSgmWke5AWY=; b=zk2GyPuLv/CULvPLi8yopdSODYUTrhGxZKZk8dd8mzHUNuBSoZcHm43puFTCkFjFXm8uD0 EKzG/04UrVUW5/s+MKyPIecaj7TnLKSsJhra2w69fUBlZqCRtgex48kf84oZWv+ijO7xUB MXwsbqhdUvynljp3nafCL1enVh0Xp8d/AJUv6JgfXle0ZzSTTq8sBb6IEcWVhyy4IO8/Nf /s+UlSdE/v9xVUUZpvRTJ4pVRv9yKjQPDDR3a25XVGjttjZOmrgfZv5qsP92UwibxkupX1 ZRClx/XM9C1sf50o+COZoIqgSIL+m5BDD0Lri5/T6Nvz3L8z47TpJqgu3s7SUQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1784023971; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=iTkmerU8UE91t1uqi1Zg80dTpHp+N6TCCSgmWke5AWY=; b=UX4RPTayR35zaZYCZZkIfXYdmcBvYC+h+fQ87S32/PfxvcS+wsHmXehsVSYaPPhLzb4Uhl mvzIyqsh+iM8wJCg== From: Sebastian Andrzej Siewior To: Leonardo Bras Cc: Jonathan Corbet , Shuah Khan , Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , Waiman Long , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , Brendan Jackman , Johannes Weiner , Zi Yan , Harry Yoo , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , Qi Zheng , Shakeel Butt , Axel Rasmussen , Yuanchu Xie , Wei Xu , "Borislav Petkov (AMD)" , Randy Dunlap , Thomas Gleixner , Feng Tang , Dapeng Mi , Kees Cook , Marco Elver , Jakub Kicinski , Li RongQing , Eric Biggers , "Paul E. McKenney" , Nathan Chancellor , Miguel Ojeda , Nicolas Schier , Thomas =?utf-8?Q?Wei=C3=9Fschuh?= , Douglas Anderson , Gary Guo , Christian Brauner , Pasha Tatashin , Masahiro Yamada , Coiby Xu , Frederic Weisbecker , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-rt-devel@lists.linux.dev Subject: Re: [PATCH v4 0/4] Introduce Per-CPU Work helpers (was QPW) Message-ID: <20260714101248.hV06z2cr@linutronix.de> References: <20260519012754.240804-1-leobras.c@gmail.com> <20260520130903.Ebsd4aUa@linutronix.de> <20260713080723.XOTiibfG@linutronix.de> Precedence: bulk X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On 2026-07-13 18:17:23 [-0300], Leonardo Bras wrote: > IIRC there are multiple users of this mechanism around the kernel. I > remember picking the first three (swap, slub and memcontrol) as examples of > how to use pwlocks (QPW at the time). With the concept proven, I could then > proceed to work with other potential users to replace it. (We ended up > dropping memcontrol in the process) > > The main idea is to replace as many potential users as possible to reduce > as much as possible the amount of IPIs in isolated cpus, and allow Linux > to run workloads which require much lower latency. Right. I am not entirely opposed to this idea. If you can't improve the situation by other means I would consider this as the last resort. If the mm folks are on board with this, then even better. > This idea came as a general solution to a bunch of latency violations > Marcelo and I were coming across. > > Thanks! > Leo Sebastian