From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 97B261632DD for ; Wed, 14 Oct 2026 00:10:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791936621; cv=none; b=DBC6n/VnrVhszVAtuHigQFHx0PIwYPAhmjw9fUOSNBF4BgsJupOy/deoIw+IYutK/3MeO5+1hquooP3A3+m2v+lD63TVGJSlkrjxhNcvTuulXs0HlL+S2bI6UFJ2Cr1/x8MH5i1ip4Iqg8KhToa+oQqyfXm27DeIduJtRwEpIxk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791936621; c=relaxed/simple; bh=LlBlzJw6I/fqV8kyE2w27pOcQxtvQEN14pch6ytVYOo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=U4SLBJJfgGFewlOzI1g/q3N0ZhIadJ64Cl2D/wPFrQIOmTshVRyN8TjP0ctoCAdmRWsqbm7v1xZYW62dfqCgu6p+OD1dlljEcNyhv2/9VEEUK1EyM/ZrOMCXXcFihxCOTC8Xeg24bccY+jvW6rxKs1lLnLBaGOz5F4GXkfadoEk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZP4EfKUW; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ZP4EfKUW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4B4671F000FF; Wed, 14 Oct 2026 00:10:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791936618; bh=z+tM5slpbKPsasUGwVhQ3lezL7cs5zFWMkBfCs77HNY=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=ZP4EfKUWSo+CgEYy4ewm1ypXx/l+9znvTg4BHHGn7q8r8Q7V/I2gBPqDGTmQarC7s ErbW6C+m49aS0vmqB6hMwXDg70DwO3OfXF+ksuDjtR4HV81JziGJZtdvF04yCWz5LV 96FaBumLAn7UznlS1p62J/Cz4MqFjhZy+17amrta8Cm2B0/qIsEk94MInYyTqOQUEJ 4AxNaTWH6kTOkasF7ct1l9rkDYVV9Wdsy0KoVLgt7QgUdGUHe5MAFeKuHIAAgpp4hw V8fH5Ls/YK8CM2NOe7RrCpVS9/ZqObSSZJcOed6JzgpSWekmwu810j34YTZn6FNN4a nDM4pDvr5B4FA== Date: Wed, 14 Oct 2026 01:10:16 +0100 From: Harry Yoo To: Linus Torvalds Cc: David Hildenbrand , Kiryl Shutsemau , Ilya Gladyshev , Matthew Wilcox , Lorenzo Stoakes , Luis Chamberlain , Linux Kernel Mailing List , Linux-MM , "Paul E. McKenney" , Pedro Falcato Subject: Re: Improve page refcount scalability Message-ID: References: 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-Disposition: inline In-Reply-To: On Tue, Oct 13, 2026 at 11:43:14AM -0700, Linus Torvalds wrote: > Comments? There should be a limitation on how much memory can be submitted to RCU by the page cache, otherwise will be a corner case where we have too much unreclaimable memory waiting for the RCU subsystem to free them. There's a similar feature, dirty throttling: when a process dirties memory in page cache much faster than the storage can handle IO, the kernel throttles it, otherwise it'll allow generating unbounded amount of unreclaimable memory. For the same reason, when a process tries to create RCU-delay-freed pages much faster than RCU can free memory, the kernel needs to limit that. -- Cheers,e Harry / Hyeonggon