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 1FBD742A140; Mon, 27 Jul 2026 23:59:29 +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=1785196771; cv=none; b=sXqunAcDoDw7vkj81QvkPF/PY45HENVa11xVUkTPJ6Ub0wnIVbBXkcOFGFu6XBy0Ve/Wi/pVLW5B7OFvVTFOjo3irNcDFa+DG9k1KT9XrmMNtzJg5G1qQR2JqN7zHsHU5lJCgZ5z4sRI+2M9E6HEU8LTIYSDiCLMVbvnO71xLWI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785196771; c=relaxed/simple; bh=3y7ZqRFLA5hc0RMIwm6TIsIB5DxmwHyMxE57lOCkxjo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JXyP+4k1xViqgEkx/QCjc8UAIgSSYsEflyBZMtOdF8zdfOEmIe1HfKn0tMk4OB2qa7PDVIKWVTzfngMf3Qho/Np8D3J/0Z62P+9U1aCmW5ARciGriQ5hbBX832o1RV0+BSWzTYHvBd+4OfqQcD5hGYXuB6Wvxy46PD/F/oDapu4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=j7CVbejW; 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="j7CVbejW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 14F031F000E9; Mon, 27 Jul 2026 23:59:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785196769; bh=CflxV47qfVfUx0JJR1VtbTQOpBhDDaq8i8LFF5znoYg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=j7CVbejWrjp2jr+HvQnk4xenwKqlsl0ldDmXYG87J0qTxQu5UJuaBmrxz58dSHjJd 3ybZDF1mgWEnAUl3OjButj8RpXIixKfh+jSJiYxviGVwTtLqfpLeju19VTmJUIeytv mj5Bf1yTzjYQUDX2LKHOwt0Kt3W0if5Fq8rh+ZOfceIbCRnikmZHg3G3La+aFaj2zs y2VlcPEw/mJGYZLWgP/wZTSKJBGgCT61l1LAtWmjLjqucSVMa002t9US2Ad8uxMzO3 3INU7qQhv7J8ZONvMYuvFI19a9JK0eMB6Dk/gsW5WHnp0L/PUDWgHhvctVx4hUZe/V 4hpxF0KTlx1Dw== From: SJ Park To: pratmal@google.com Cc: SJ Park , akpm@linux-foundation.org, vbabka@kernel.org, david@kernel.org, corbet@lwn.net, 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, ljs@kernel.org, liam@infradead.org, rppt@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org Subject: Re: [PATCH v3] mm/page_reporting: Add page_reporting_delay_ms module parameter Date: Mon, 27 Jul 2026 16:59:25 -0700 Message-ID: <20260727235925.93406-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260727230545.262579-1-pratmal@google.com> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Mon, 27 Jul 2026 23:05:45 +0000 pratmal@google.com wrote: > From: Pratyush Mallick > > Currently, the free page reporting uses a hardcoded delay of > (2 HZ) between reporting intervals. While this is a reasonable > default, it lacks the flexibility to adapt to varying guest workloads. > > A low delay allows aggressive memory reclamation, returning unused > pages to the host as quickly as possible. However, during spiky > allocation/free churn, this immediate reporting can lead to a severe > performance penalty (nested page faults) as the guest re-allocates memory > that the host has just unmapped. In these scenarios, there is benefit > from increasing the delay to batch free pages over a longer window, > absorbing the churn without hypercall and re-fault overhead. > > This patch exposes the delay as a module parameter: > /sys/module/page_reporting/parameters/page_reporting_delay_ms, measured > in milliseconds and defaults to 2000ms. Makes sense to me. > > Signed-off-by: Pratyush Mallick Reviewed-by: SJ Park Thanks, SJ [...]