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b=sPdfZD3C75x+zdwpX980Cb5uMMaWdXbkRoTNOzjDZ2QZ1GzduGr4Y/46wyyZ2WzJ0 NBtfmwq/HIUpUfnA02BVvZUpSBiGzw9Y91N4txja77ie89aYDKsuSst3as8PAdINh0 BEm/IeUUCHR5Wx3iwauiU+93Yw3yobj41jjYyDTc= Date: Wed, 23 Oct 2024 16:24:47 -0700 From: Andrew Morton To: Jim Zhao Cc: willy@infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/page-writeback: Raise wb_thresh to prevent write blocking with strictlimit Message-Id: <20241023162447.2bf480b4ce590fdeb8b6c52d@linux-foundation.org> In-Reply-To: <20241023100032.62952-1-jimzhao.ai@gmail.com> References: <20241023100032.62952-1-jimzhao.ai@gmail.com> X-Mailer: Sylpheed 3.7.0 (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-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: D0ED180002 X-Stat-Signature: ki1bch4btdn8h3fq51kk63kc81naw5kr X-Rspam-User: X-HE-Tag: 1729725855-487509 X-HE-Meta: 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 sVr508SZ OGMmEXOD0NbmkV8C/xelIvNnXaBMpwrjr3vm/e3aQugmf/FC7vZmAck9vrYjvQzfOG/oA0giDltRy+a2XS2SbrjzHroTP96CHg/Y2nssI9ps3gltRsu+RH07Q+wRDm9+X65QK4ULdaWWztT9w5Kvw9M46b7bFGrZXvXcWCqxzEMQWBaklRiTD7z8Iro8NZLHNx0Gdz9h1tRBY+wWPFxTTOeDBqpF3Oy5TICr0gSrAQLYRQaCmHlUyhtBKOYIp7yzMOTMDswIJThWBgIftn4JXL1Jh+JzMgzOeVz42XrChSP3VxX7zw7W25oeZSuJvzMHxxH9gl9c/iiYb2M43bX8L1+wJYD3ivNfU22ZW9FoZdA03pcnZP9e5mgpoQdphYVXXNe9y0VH5/dlXoG6yW0PGeYQqTcfbWFQIuPOK 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 Wed, 23 Oct 2024 18:00:32 +0800 Jim Zhao wrote: > With the strictlimit flag, wb_thresh acts as a hard limit in > balance_dirty_pages() and wb_position_ratio(). When device write > operations are inactive, wb_thresh can drop to 0, causing writes to > be blocked. The issue occasionally occurs in fuse fs, particularly > with network backends, the write thread is blocked frequently during > a period. To address it, this patch raises the minimum wb_thresh to a > controllable level, similar to the non-strictlimit case. Please tell us more about the userspace-visible effects of this. It *sounds* like a serious (but occasional) problem, but that is unclear. And, very much relatedly, do you feel this fix is needed in earlier (-stable) kernels?