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 A889846C844; Wed, 5 Aug 2026 12:03:48 +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=1785931429; cv=none; b=XG2Beab6FHj/KiYtQGA837TLJG+qIHWtf/UgNNS8OqnkAQmhtrrY+s+AkzrZ6GYASgWLm+n19Xj4us4neBwo1H/+l3Hux5zQwzmlCJZ9svreFGQLbSld0m5jzpDMuC6e8xWmz8Bw3Mqr1t2ShnrC+0vOazC7d0gs2tV0cc6lP5k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785931429; c=relaxed/simple; bh=A5HLaSgjhgjPaEmz5Bda1jcHu9p18ZGtwEN522g1xE8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=qwxxCH0e0VA55W3lBV3meMAJdB2dETLzW/pCaUjwQz6jjJtw5eK5u1we9myPD8FUWt6LxaxJ1n99g/uOENItnjvXY9hfNkQf1Xo8gkiwTvRkbQyV1ftyxi8KWkOfneq1yRtLM5WYsrRdlbN4RM6zZB75L9nEgKaXdvxKsfcCiUI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NDYF/i3G; 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="NDYF/i3G" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB64C1F00ACA; Wed, 5 Aug 2026 12:03:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785931428; bh=/TxnOeGfIBpnExbybgGUK7PctnBzRbPKKrr+zPKrO7c=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=NDYF/i3GHNA+/IHT24tL5hwQavM5fu/ZoSDW+J9bbFkcuRP8SsjnM15hTBdETAfkV Wakg7UP63JLO7jYu2GYy/+4FSFdzK2IX6KKeddR7B26sh1Db8DtfOj2SQ5wVgBi2xx uW2Wail8EKoiFOuj38AdJp+kl07jMXgbGa2gbY0HVGuxg/0BPNAouvXX7dqzRdnOnx jvR41xDH0Vp4VOFDL3/uzlyafGPdiBMP7uhbK8fTFRY+zsXgkILJeXMIZuVAkDDIxP vn6U11lvFwg0nP2qEx2bNvUcI/86FTiemcTKX/YLgMiuWe2OpWdeUnd3/s3WIBfnQm 2WmAhmyrhRrOQ== Message-ID: <0b48002f-8e2c-41b3-b8ef-69f200b02330@kernel.org> Date: Wed, 5 Aug 2026 14:03:41 +0200 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] mm/page_reporting: Add page_reporting_delay_ms module parameter To: Andrew Morton , pratmal@google.com Cc: vbabka@kernel.org, sj@kernel.org, corbet@lwn.net, ljs@kernel.org, skhan@linuxfoundation.org, anshuman.khandual@arm.com, gthelen@google.com, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, liam@infradead.org, rppt@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org References: <20260731193705.2902728-1-pratmal@google.com> <20260731143420.0787387ce2ca120ecee15338@linux-foundation.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/31/26 23:34, Andrew Morton wrote: > On Fri, 31 Jul 2026 19:37:05 +0000 pratmal@google.com wrote: > >> Free page reporting currently hardcodes a 2-second interval between >> reports. This rigid delay cannot accommodate diverse guest workloads. >> >> This patch introduces a module parameter, page_reporting_delay_ms >> (default: 2000), allowing users to tune the reporting rate: >> - Lower values enable aggressive memory reclamation by returning unused >> pages to the host immediately. >> - Higher values help batch pages during spiky allocation/free churn, >> reducing hypercalls and nested page fault overheads. >> >> Setting the delay to 0 is safe and execution is strictly gated by: >> - reporting is only triggered by high-order page frees. >> - expensive hypercalls are bounded by a slot capacity watermark check >> before proceeding. > > This conflcits with the just-upstreamed 0b45f6927a1 > ("mm/page_reporting: use system_freezable_wq to fix UAF during > suspend") > (https://lore.kernel.org/20260721005603.1710551-1-linkl@google.com). > > Please review my resolution: > > --- a/mm/page_reporting.c~mm-page_reporting-add-page_reporting_delay_ms-module-parameter > +++ a/mm/page_reporting.c > @@ -48,7 +48,11 @@ MODULE_PARM_DESC(page_reporting_order, " > */ > EXPORT_SYMBOL_GPL(page_reporting_order); > > -#define PAGE_REPORTING_DELAY (2 * HZ) > +static unsigned int page_reporting_delay_ms = 2 * MSEC_PER_SEC; > +module_param(page_reporting_delay_ms, uint, 0644); > +MODULE_PARM_DESC(page_reporting_delay_ms, > + "Set page reporting delay in milliseconds"); > + > static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly; > > enum { > @@ -57,6 +61,13 @@ enum { > PAGE_REPORTING_ACTIVE > }; > > +/* schedule work for page reporting */ > +static void page_reporting_schedule_work(struct page_reporting_dev_info *prdev) > +{ > + queue_delayed_work(system_freezable_wq, &prdev->work, > + msecs_to_jiffies(page_reporting_delay_ms)); ^ just double checking whether that is indented properly . Acked-by: David Hildenbrand (Arm) -- Cheers, David