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Received: from DESKTOP-5N7EMDA(mailfrom:ying.huang@linux.alibaba.com fp:SMTPD_---0X-oES69_1773308534 cluster:ay36) by smtp.aliyun-inc.com; Thu, 12 Mar 2026 17:42:15 +0800 From: "Huang, Ying" To: YeeLi Cc: akpm@linux-foundation.org, david@kernel.org, dan.j.williams@intel.com, linux-mm@kvack.org, joshua.hahnjy@gmail.com, linux-kernel@vger.kernel.org, Jonathan.Cameron@huawei.com, linux-cxl@vger.kernel.org, dave.jiang@intel.com Subject: Re: [PATCH] mm/mempolicy: add sysfs interface to override NUMA node bandwidth In-Reply-To: <20260312091207.2016518-1-seven.yi.lee@gmail.com> (YeeLi's message of "Thu, 12 Mar 2026 17:12:07 +0800") References: <20260312091207.2016518-1-seven.yi.lee@gmail.com> Date: Thu, 12 Mar 2026 17:42:13 +0800 Message-ID: <878qbxpeoa.fsf@DESKTOP-5N7EMDA> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 1D6F2160006 X-Stat-Signature: z56f3utxyqm8r8aqahgrauwznbdcskfw X-Rspam-User: X-HE-Tag: 1773308538-286316 X-HE-Meta: U2FsdGVkX1++bxpkMD5oT4PqYGunS5lGEZ9lns8O4JBi8GwiNIEdhkk16hG58ngLvWfUHopqbbxVZKQ1tyHyQvhRoFmH5Y2C8AQkS8xXDKSG3WgJHhPfh0VqNEII/vd8anAnFxi+l5FrtAutNuNfQuZZDmJLWpkwhmEwzSvhGH++mN7VJEexQ+I1BVXxonwlQ1lbCozyMATmRtgjQliDYPZUug3V23bREcpewiuYBzAlUCsyEuv8TGFztj1YyuXgIw7ZE5mDDHbCxsh6pLJ8MM76oIVM4suCUin+KSDLubKygxJEJUpv+rCXIsXoUsMmgzMoJlebD3jr/3NsapJ8le+B/l6hc2YpfLg8hRpAF5/lsmc7V15J3BK2mmE0EOOzy746qkLj1W0O9yZwlvcxl1CMdESxglpApZ6KDQf9bcbpjfxdsmQCHJQPguL/Q67d563qA7dZ1OjNi/zgLWdiq9h+RSF6iCzqWhg14rxgjZkyiStYEjUBGALSkxVFIOwbdVOdBW9VVC+GZ+1tzB1M7ooydlljbGjkY7qBwV9dozBN1smf94RZhNX/DvrAl1DyK/SD3rfHuNX+jcqiCAhponey0UZ7brdC1u9lSgW+wfo+hoRx69NL1pt2zZANnLEU4sJGbq8WuKNgRM3vhQAhnEsZ0nGKYVUVukjQOItSNCZsKm/uudrrJuByvbDsOUaU53oJMsI5fVfEOq+g1cej4maXTXQ/6lOnLCdiHm84R2bA8jIx/YN7+3h6LWtDRpqoZvmvdwWnKO2NXxHhPSyLbgjOUmoCskL9HCVIz/Y6JL5ekve1bTlUPSC76FyTuDzBJH3fZ4WMD7xozCuBZ4v38u+3osBztvnB3HWsK2eURkUS5JQvVCjk5kdc0dF//ApY3+JJJbmvsrkwk2exEFrSZgCrhXgx78aiLD58GBZh17Uy7q2+evvfQzCZankeB1FoJX2KLsZJGc37N7yqPv5 6P1brPfR mgWBPBaktKQBIGpjoiUgA9b1XjUqZAZXj1hIGQqmM+aDWaVwi74Qgfg+VS0e22bdE23GzDBciW+86cDjo/EyLoLqDc2K7PhsevbSjpfR5pyhqFXTQrjcVd4YtguIzB06PcFq2pL2wdcAmnWuusjumqxnf2eFGN0LPcVt3hGTunr2jOa7juzG6K1HsGp5QCRTdcvVovg1eygaXJiGw9AzIu7FNN9kO4Q4zWibM1Y8JsOePToZDTVDHe/4026BKU6G8fjUDPuYUeh95TDp8cUJ/waP5uXna2SginIPTfK6fv4HfuwqCPRM1sSRoS4amKuF2mzFMBxWMRKO8gJvsyRnWzjlWHoiqIb7S2nN5aA+gEJGPLnT4ZcTC/402iDpOT0AFQsoo2o2MxQ9LDFXBpL+V9vq3AqvnjrEBDxdb Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: YeeLi writes: > From: yeeli > > Automatic tuning for weighted interleaving [1] provides real benefits on > systems with CXL support. However, platforms that lack HMAT or CDAT > information cannot make use of this feature. > > If the bandwidth reported by firmware or the device deviates from the > actual measured bandwidth, administrators also lack a clear way to adjust > the per-node weight values. > > This patch introduces an optional Kconfig option, > CONFIG_NUMA_BW_MANUAL_OVERRIDE (default n), which exposes node bandwidth > R/W sysfs attributes under: > > /sys/kernel/mm/mempolicy/weighted_interleave/bw_nodeN > > The sysfs files are created and removed dynamically on node hotplug > events, in sync with the existing weighted_interleave/nodeN attributes. > > Userspace can write a single bandwidth value (in MB/s) to override both > read_bandwidth and write_bandwidth for the corresponding NUMA node. The > value is then propagated to the internal node_bw_table via > mempolicy_set_node_perf(). > > This interface is intended for debugging and experimentation only. How to use this new interface? Can you provide an example? --- Best Regards, Huang, Ying > [1] Link: > https://lkml.kernel.org/r/20250505182328.4148265-1-joshua.hahnjy@gmail.com > [snip]