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b=t1KLx/NdrNsWfrGrfuTViwSseXvCj72+/EPMEMP3/KwAxs1cYn9RV823rHFgsBmi5 UvvyQ/UGaVRoFpZoVzVZhpfp94aqoQABL4891Q/kvGyYENNSw36h4BjGE2Nd7vzsy2 iHpAqjPkGWZyawz7rhr4NREdKl1PlOSMr44ZcnRE= Date: Sun, 22 Feb 2026 11:42:01 -0800 From: Andrew Morton To: Wei Yang Cc: will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, peterz@infradead.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, Qi Zheng , "David Hildenbrand (Arm)" Subject: Re: [PATCH] mm/mmu_gather: define RCU version tlb_remove_table_one() in CONFIG_MMU_GATHER_RCU_TABLE_FREE Message-Id: <20260222114201.095379dd766b68dcecbab1c5@linux-foundation.org> In-Reply-To: <20260222004512.839-1-richard.weiyang@gmail.com> References: <20260222004512.839-1-richard.weiyang@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: h4gxue13k3zjkferexp1yci7nttg4m7n X-Rspam-User: X-Rspamd-Queue-Id: 7AABF40010 X-Rspamd-Server: rspam01 X-HE-Tag: 1771789323-634792 X-HE-Meta: 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 WNdkxIi0 J0ydKzq9zf3EeQYETpW+FbI5eUa4b1w346NVvy/19tx9TAwWqr1knMWsbfVW6LCfkgHFToEX50T4aPfQic6J36Zko1wVpp8unjfNPKjJJplLbFKr2AFYpLXb2BkczlZVt39Cc1Eq7illuk6zh3CdrbkIKbXe9PWLksHuUj3KPFyPN2uHj6D5YZPdYfKNYdTuH/OP3IYS0EuiG+0pW5p2tuqw+dSSOxcdOiL/qXqLZyp5WoKOshV+RSo9XU1I+CGBWB2e/V298XCBzKD9vBlo9QvO7FRx2GsdIFXnyhBgLhW1Q7XCzzeKogHCU8hOZ5u+q7tz0a16pvd6UXTGyvL+yTOXNhA47j6OvL/180u+ZoqrzkKexCPPQZhxpU31DbNxhs2Nd+l8d/41CrFo= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, 22 Feb 2026 00:45:12 +0000 Wei Yang wrote: > Before commit 718b13861d22 ("x86: mm: free page table pages by RCU > instead of semi RCU"), the page table pages will be freed by semi RCU, > that is: > > - batch table freeing: asynchronous free by RCU > - single table freeing: IPI + synchronous free > > This commit introduce a RCU version for single table freeing to support > PT_RECLAIM. While it is not necessary to limit the RCU version only in > CONFIG_PT_RECLAIM. It is reasonable to asynchronous free single table by > RCU if CONFIG_MMU_GATHER_RCU_TABLE_FREE. > > This patch moves the definition of single table freeing in > CONFIG_MMU_GATHER_RCU_TABLE_FREE, so we have both RCU version > batch/single table freeing if CONFIG_MMU_GATHER_RCU_TABLE_FREE. What are the expected (and measured!) benefits of this?