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[77.129.29.205]) by smtp.gmail.com with ESMTPSA id v192sm13645238wme.24.2019.05.13.03.30.06 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 13 May 2019 03:30:06 -0700 (PDT) From: Daniel Lezcano To: tglx@linutronix.de Cc: linux-kernel@vger.kernel.org Subject: [PATCH 3/9] genirq/timings: Optimize the period detection speed Date: Mon, 13 May 2019 12:29:47 +0200 Message-Id: <20190513102953.16424-4-daniel.lezcano@linaro.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190513102953.16424-1-daniel.lezcano@linaro.org> References: <20190513102953.16424-1-daniel.lezcano@linaro.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If we have a minimal period and if there is a period which is a multiple of it but lesser than the max period then it will be detected before and the minimal period will be never reached. 1 2 1 2 1 2 1 2 1 2 1 2 <-----> <-----> <-----> <-> <-> <-> <-> <-> <-> In our case, the minimum period is 2 and the maximum period is 5. That means all repeating pattern of 2 will be detected as repeating pattern of 4, it is pointless to go up to 2 when searching for the period as it will always fail. Remove one loop iteration by increasing the minimal period to 3. Signed-off-by: Daniel Lezcano --- kernel/irq/timings.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.17.1 diff --git a/kernel/irq/timings.c b/kernel/irq/timings.c index 250bb00ccd85..06bde5253a7d 100644 --- a/kernel/irq/timings.c +++ b/kernel/irq/timings.c @@ -261,7 +261,7 @@ void irq_timings_disable(void) #define EMA_ALPHA_VAL 64 #define EMA_ALPHA_SHIFT 7 -#define PREDICTION_PERIOD_MIN 2 +#define PREDICTION_PERIOD_MIN 3 #define PREDICTION_PERIOD_MAX 5 #define PREDICTION_FACTOR 4 #define PREDICTION_MAX 10 /* 2 ^ PREDICTION_MAX useconds */