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Wed, 15 Apr 2026 05:50:09 -0700 (PDT) MIME-Version: 1.0 References: <20260409160243.1008358-1-hch@lst.de> <20260409160243.1008358-9-hch@lst.de> <7f0d072b-97a7-405f-bff5-d3819de2e3dd@linux.alibaba.com> In-Reply-To: From: Sandeep Dhavale Date: Wed, 15 Apr 2026 05:49:58 -0700 X-Gm-Features: AQROBzBdnyNeg6M7eBa34eLrstKbL-D014vWbc0uebEOU17jGRgdz997IpSMUAE Message-ID: Subject: Re: [PATCH 8/8] RFC: use a TASK_FIFO kthread for read completion support To: Gao Xiang Cc: Dave Chinner , Christoph Hellwig , Tal Zussman , Jens Axboe , "Matthew Wilcox (Oracle)" , Christian Brauner , "Darrick J. Wong" , Carlos Maiolino , Al Viro , Jan Kara , Bart Van Assche , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 5CA9020005 X-Stat-Signature: sgwgup1tdy7d5ni6uu6ra71kkgxwappd X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1776257411-654940 X-HE-Meta: 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 isJwysY1 T5lXxhCX6Naw1SoQjMG6RT1i5dPgi4/AMRDIePzL9FrlHqxbUYjlbhP3ns1lrH9ILohVCIPi2+uAedmlR1Z9/ZU9NBEfBSSEG9f0HR8FSjLtZR+qcepo8dgqp6ljHOgxa6rr4Ri5jvcz6KX+5cLjTNdGzyY5PecLKQUgLUOkoAOa9rEKvu/RFOoPipUR1P8nUgicMIv53j85FOgorn6RU4ryJNf6rg41iaL3OWAcySG4m+HE+oMUD2yTyEufHK0J8IHHmMsfg/WbyZ6Uz5FLQEuLnAxRcp6on++9J Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > Basically what we want is to get a non-atomic context instead of > using the current softirq context for read post-processing and > switch to the task context immediately as you said, because: > > - Our post-processing needs to work in task contexts since > advanced features like compression deduplication need it; > > - Even regardless of our specific requirement needing task > contexts, using a dedicated task context for read > post-processing is much better than run in the original > softirq context: > > - Algorithmic work could take extra time (especially slow > LZMA algorithm could take milliseconds on low devices > (however, we need a common workflow for all algorithms, > including fast algorithms like lz4) and verify work for > example); and long processing time will interfere with > other remaining softirq tasks like sound-playback > / network softirqs; > > - If it is then deferred to softirqd, it just makes this > latency issue _worse_. Yes, this was the reasoning when I narrowed it down to per-CPU kthread approach. Patch has helped reduce app launch times which has a direct user impact. > > But anyway, I think nice -19 can be evaluated if Sandeep have time, > but such nice value should be set by the filesystem instead of > the userspace since the reason is as above. > I will find some time to re-do this again, including setting nice -19. -Sandeep.