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b=Kb5TwCTDykxh+F0BV/zgxvFh9tyji0+FhmpBbQtL7rFewAWc7VOBkdTfx6f1aAJz9 /Y2iSzjuQL2djCeSnUjpGmVn6UXcLuYThCrQZ/FZK6/VmIgurIJ1EvTp3LLc8O3J8s VyJEr5d3wXzvcqDd8pzf2Vwi1gPU6nT6xnXRzujI= Date: Fri, 25 Oct 2024 17:02:22 -0700 From: Andrew Morton To: Jim Zhao Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, willy@infradead.org Subject: Re: [PATCH] mm/page-writeback: Raise wb_thresh to prevent write blocking with strictlimit Message-Id: <20241025170222.0ced663e778935946ea1c9fa@linux-foundation.org> In-Reply-To: <20241024072919.468589-1-jimzhao.ai@gmail.com> References: <20241023232042.f9373f9f826ceae2a4f4da35@linux-foundation.org> <20241024072919.468589-1-jimzhao.ai@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-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 4602F2000F X-Stat-Signature: ibf4uj5tdorp65gj1s9qc6f14zwhaoni X-Rspam-User: X-HE-Tag: 1729900923-130294 X-HE-Meta: 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 0CA2kWRf qYjDL5jiEzwc+HtA/Li+ZFW+y2AOUxZLOuLdBQNMdWtkDmRRVtRC3mflXRnC6GGWbMK+h1UJrHFwlGzcHa1doT9M8PBk6CA/K1FglyDJyrxHH+onAvmODaX7IZbad+6EIG5fRs3O7HXnFnI8wFJUW8NKbbf+K6iDNeQD3q0y16kFJWZNfaNVe/8x1YVROUwcLWYAkph/XyYJv+i93DhQHL5kwUrSXgcFLEUFwQw6ILXNq53/u3vPIq5Y5pbiFN/JOz65Uecd1my2KemjcrzNQCQBbljtaFQrGDyAF9idgJlkmBVBfWd1L+P3gTrLrZGgHpQGKdlFGkcH53yEvnVVqnhjO40fFzn85EcDqN09LU6cojwW8hOBshbPlfR6K3bs2AXBq 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 Thu, 24 Oct 2024 15:29:19 +0800 Jim Zhao wrote: > > > 2. FUSE with Unstable Network Backends and Occasional Writes > > > Not easy to reproduce, but when it occurs in this scenario, > > > it causes the write thread to experience more pauses and longer durations. > > > Thanks, but it's still unclear how this impacts our users. How lenghty > > are these pauses? > > The length is related to device writeback bandwidth. > Under normal bandwidth, each pause may last around 4ms in several times as shown in the trace above(5 times). > In extreme cases, fuse with unstable network backends, > if pauses occur frequently and bandwidth is low, each pause can exceed 10ms, the total duration of pauses can accumulate to second. Thanks. I'll assume that the userspace impact isn't serious to warrant a backport into -stable kernel. If you disagree with this, please let me know and send along additional changelog text which helps others understand why we think our users will significantly benefit from this change.