From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752723AbcFNQiD (ORCPT ); Tue, 14 Jun 2016 12:38:03 -0400 Received: from www.linutronix.de ([62.245.132.108]:35386 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751364AbcFNQiA (ORCPT ); Tue, 14 Jun 2016 12:38:00 -0400 Date: Tue, 14 Jun 2016 18:36:01 +0200 (CEST) From: Thomas Gleixner To: Nicolas Pitre cc: Daniel Lezcano , shreyas@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, peterz@infradead.org, rafael@kernel.org, vincent.guittot@linaro.org Subject: Re: [PATCH V4] irq: Track the interrupt timings In-Reply-To: Message-ID: References: <1460545556-15085-1-git-send-email-daniel.lezcano@linaro.org> <57600866.4070601@linaro.org> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 14 Jun 2016, Nicolas Pitre wrote: > On Tue, 14 Jun 2016, Daniel Lezcano wrote: > > If the storage is a bit larger (let's say 16 values) and there is no memset > > and the sum is not computed, at least we need a count for the number of values > > in the array before this one is fulfilled, otherwise the statistics will be > > wrong as we will take into account the entire array with old values, no ? > > The point is not to change from 8 to 16 entries, but to store raw 64-bit > timestamps instead of computed 32-bit deltas. Whether or not those > timestamps are too far apart and discarded can be done at idle entry > time. Correct, and you don't have to know how many timestamps are in the array simply because if it is cleared at init time, then any not yet set value will create a large gap, which you filter out. The point is to make the fast path overhead as small as possible. And if that's just a store and index increment, then it can be inline and not a function call. Thanks, tglx