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 9F7B248166D; Wed, 21 Jan 2026 12:32:36 +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=1768998756; cv=none; b=qXLNkT38hQgJqhsDuW9xoyUM01RSCURaxVIzYg5Fq/tYsy8fPRI2t0owKuS53H01FpMx0MrytjWN6YHgrwMqfjAi9XRouIdOBBLr7DiuE3sCW7KAbFg/m2ErczzwJL9nveMfd07AYmfd0uYB12Ffdp0QMDlAGw+uC6UNgjJdVI4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768998756; c=relaxed/simple; bh=Urvd/N57mhTCzV1hIjinqqtH/SRw4kq7Kx76LANoLZw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=q2GRbrfaeJQ54viyny4KpfNwZG0mCm/pDeE8E4LGpXF/U39bA79oTCifuUpvwCigX263UpXRy5tCOpgNF/I0zHzHNE3QE/a43HIPFaMwW3AkvZJyfJZw4DDA9e/VDYixOpyQ5g0uG1H8IJ5aHGj78Q3FiXyM/B+k5ubnyj2tdLc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Z3kvy/nr; 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="Z3kvy/nr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ACF1BC116D0; Wed, 21 Jan 2026 12:32:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768998756; bh=Urvd/N57mhTCzV1hIjinqqtH/SRw4kq7Kx76LANoLZw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Z3kvy/nrtc1ODOdK9vKo/8F+DqtLW8vS+My2lkW4TBV/LV9AqWY20lPS+4Kwd7sKu peVDMJsmgI/nDfqRZw+JKl4cxiyWX+uR1cUh2TtbbKI+C//BubJ30civbuNnWaIQx3 IKjUDwqf7ZA+26d2GK/zjj0DVhoZeeLpEs+eIQTDN7q6VqaauCWLIXiJILerttyumA UhT/nB7R7pLcxh6RuIxudUFVc79gyTia1AysbtMswNY6me1dELYKK8M2hiR+mgCBz1 +rMrHS5id45rCl1uNxMoG4KaNuNc38uGNf4szzh9FP1u9wbc8o9qMPWmQYjQdvg/s8 l8X3BFRa2qWIQ== Message-ID: <54a7e6ff-b3bc-4de4-af26-03fa1400d5f9@kernel.org> Date: Wed, 21 Jan 2026 13:32:29 +0100 Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/8] Introduce a huge-page pre-zeroing mechanism To: David Laight , Li Zhe Cc: akpm@linux-foundation.org, dan.j.williams@intel.com, dave@stgolabs.net, ankur.a.arora@oracle.com, fvdl@google.com, gourry@gourry.net, joao.m.martins@oracle.com, jonathan.cameron@huawei.com, linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, mjguzik@gmail.com, muchun.song@linux.dev, osalvador@suse.de, raghavendra.kt@amd.com, wangzhou1@hisilicon.com, zhanjie9@hisilicon.com References: <87wm1ih5kb.fsf@oracle.com> <20260120062706.91078-1-lizhe.67@bytedance.com> <20260120094744.5d92e34a@pumpkin> From: "David Hildenbrand (Red Hat)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/20/26 10:47, David Laight wrote: > On Tue, 20 Jan 2026 14:27:06 +0800 > "Li Zhe" wrote: > >> In light of the preceding discussion, we appear to have reached the >> following understanding: >> >> (1) At present we prefer to mitigate slow application startup (e.g., >> VM creation) by zeroing huge pages at the moment they are freed >> (init_on_free). The principal benefit is that user space gains the >> performance improvement without deploying any additional user space >> daemon. > > Am I missing something? > If userspace does: > $ program_a; program_b > and pages used by program_a are zeroed when it exits you get the delay > for zeroing all the pages it used before program_b starts. > OTOH if the zeroing is deferred program_b only needs to zero the pages > it needs to start (and there may be some lurking). Can you point me to where was that spelled out as a requirement? > > The only real gain has to come from zeroing pages when the system is idle. > That will give plenty of zeroed pages needed for starting a web browser > from the desktop and also speed up single-threaded things like 'make -j1'. I am strictly against over-engineering any features that hugetlb benefits from only. -- Cheers David