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Tue, 14 Oct 2025 03:13:47 -0700 (PDT) Date: Tue, 14 Oct 2025 11:13:46 +0100 From: Matt Fleming To: Jan Kara Cc: adilger.kernel@dilger.ca, kernel-team@cloudflare.com, libaokun1@huawei.com, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, tytso@mit.edu, willy@infradead.org Subject: Re: ext4 writeback performance issue in 6.12 Message-ID: <20251014101346.ep73uuigr25xu5a2@matt-Precision-5490> References: <20251006115615.2289526-1-matt@readmodwrite.com> <20251008150705.4090434-1-matt@readmodwrite.com> <2nuegl4wtmu3lkprcomfeluii77ofrmkn4ukvbx2gesnqlsflk@yx466sbd7bni> <20251009101748.529277-1-matt@readmodwrite.com> <20251009172153.kx72mao26tc7v2yu@matt-Precision-5490> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Oct 10, 2025 at 07:23:54PM +0200, Jan Kara wrote: > > Maybe I misunderstood what you wrote about your profiles but you wrote that > we were spending about 4% of CPU time in the block allocation code. Even if > we get that close to 0%, you'd still gain only 4%. Or am I misunderstanding > something? Ah, I see. Yeah that's true but that's 4% of CPU cycles that could be put to better use elsehwere :D