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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: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 0BD7B20006 X-Stat-Signature: abmkeyi7as4pghcmigx4863wezwh39wq X-HE-Tag: 1785196770-422894 X-HE-Meta: U2FsdGVkX18tWzJ7WX7aE8clMtej8cqAw2DOECmK6CYBCueUa6I4l4dgDHzCPH6l+stcSyZKl7ZPNM+JFQAQcCr71VIAIMpn/u+VfihZLQiG+H0ZsMj/ytwUip7h0mSztoghwjQC7XVFkOYWZEIJdsFW+NhB6s7cG5yGnjxNszdl41Opz2V7CCabIUq8ZfX5j+4Y5qlKwWdDpsruf10UnSZISxglZ3PrcVqR+kN9Sd3j28iJancy6aFYtrbmtWszshZpt7sOY5rUSAYXZ9o8ZL4ZosZZUhncbSWMS2HKF9wtJyXGymCm+stUTtb3vTCLokOd+I3g/1AlZ+VqH1Wv6P/VM8RxsknSC34QREp3aoh8wsrghEVj6hxb0v9rzjY9nScF8/UUrP8JYrOjtmXmDEYPAztrYp3CWLzDj8dWtbCOyBv7yuv6LDVl1Vzb9TOcfMmQ+rCb/KVNqpo7WSgZTt3nMd4sfpmobApuxbkmGDxHed2kRUAUBkaINHV3YluMOrZt0UNCG6zDzZDVEOQdkggeiiXbvOBpGhy16zWlBFq3yCe0Vp1RSVbAweP3bkpnAo2l3v+mgCC0iMljZUTd3uJ054Mho0KSI3jQ9u5Bfv9CZI3IqPi6VYonfp9qaTOGg1o7Vsq1vIPDLit9ivYGcOns9A0wUpD1B20Nzjd6byvxTwau+Y+qWBcD4ghOLrT2vmnbW49+7JLPNm1WUB+bCfdrnFgVsNz6MJXpchAm8AIc+UMDwFNuch6FhPWZaHDnJimxc5CEy76MZkH9z0AhreVRBZrq+wkBnC+TKN0JjC7CyW0yddzhTJUyfpQDPtC+46pEMz4468XDrRGWggjbBblOfeFS57452x1c7PodeGoAO/9EIPNl3BRR7sq3mbBI+NOygywgmmi6D/1mgOohAEdXuDrjcJRjQX5u5AWpJk1ezznGJyHJfJqM9vITDBEE2eMJWz7rCL/0hS7WkuK 6WLoXh+7 vwPVDIDdNTOlsRLfZTULK6MCMKS5msf3wyKL+eVDNzcYOb4RnFsT9o3JvN/cmkicI/niHkXVLoDXBz23leHX06tmeNy8LFFCrw4rrpzOOgkSkASWoz1GrEJPjJoOcc3fGFFCKti1H9I+pC2LeOq2iFLEchn26QDghempSKRDpQsMhmE0F6NLLpBXrt/XwZfILTYr/7DDcsBSUOR+x7+mawz7UmqRjqRKdthAMg9oOWxi/P84g48ERqLxa/6Jny2l3gtsmifPu87vjy2l+iXJ0DjilD0mBcIqNTdlg5yait0w4ybzHepHLUSHFCQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 [...]