From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932101AbcFNQu7 (ORCPT ); Tue, 14 Jun 2016 12:50:59 -0400 Received: from www.linutronix.de ([62.245.132.108]:35470 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751923AbcFNQu5 (ORCPT ); Tue, 14 Jun 2016 12:50:57 -0400 Date: Tue, 14 Jun 2016 18:48:57 +0200 (CEST) From: Thomas Gleixner To: George Spelvin cc: peterz@infradead.org, edumazet@google.com, linux-kernel@vger.kernel.org, richardcochran@gmail.com Subject: Re: [patch 13/20] timer: Switch to a non cascading wheel In-Reply-To: <20160614125800.18461.qmail@ns.sciencehorizons.net> Message-ID: References: <20160614125800.18461.qmail@ns.sciencehorizons.net> 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, George Spelvin wrote: > Not enough to be interesting, and the extra levels increase processing > time. If you need to shrink TIMER_ARRAYMASK to fit another flag bit, > the easier way would be to encode only the level rather than the index, > since you can derive the latter from level and expiry time trivially. We can accomodate wheel with 512 buckets with the current ARRAYMASK and that really should be enough. > A couple of really minor tweaks that could be folded in, if Thomas feels > like it: > > * It would make sense to move all the TIMER_ARRAYSHIFT/TIMER_ARRAYMASK > stuff out of patch 13 and into patch 20. The expiry code uses the pending_map already in patch 13 to avoid looking at the bucket if its empty. > * It would make sense to change the return type of mod_timer (& Co.) > detach_if_pending, and del_timer to bool. > ({try_to_,}del_timer_sync return 3 values.) We can do that as a seperate patch. Makes sense. Thanks, tglx