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charset=us-ascii Content-Disposition: inline X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250616_070337_349728_0C8CDE0D X-CRM114-Status: GOOD ( 13.83 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hello, On 14/06/25 10:04, Kuyo Chang wrote: > From: kuyo chang > > [Symptom] > The calculation formula for fair_server runtime is based on > Frequency/CPU scale-invariance. > This will cause excessive RT latency (expect absolute time). > > [Analysis] > Consider the following case under a Big.LITTLE architecture: > > Assume the runtime is : 50,000,000 ns, and FIE/CIE as below > FIE: 100 > CIE:50 > First by FIE, the runtime is scaled to 50,000,000 * 100 >> 10 = 4,882,812 > Then by CIE, it is further scaled to 4,882,812 * 50 >> 10 = 238,418. > > So it will scaled to 238,418 ns. > > [Solution] > The runtime for fair_server should be absolute time > asis RT bandwidth control. > Fix the runtime calculation formula for the fair_server. > > Signed-off-by: kuyo chang > --- Right, I would agree we don't actually want to scale fair_server runtime by frequency/capacity. Your change looks good to me. Acked-by: Juri Lelli Thanks! Juri