Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752048AbaAQA2t (ORCPT ); Thu, 16 Jan 2014 19:28:49 -0500 Received: from order.stressinduktion.org ([87.106.68.36]:44131 "EHLO order.stressinduktion.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751937AbaAQA2p (ORCPT ); Thu, 16 Jan 2014 19:28:45 -0500 From: Hannes Frederic Sowa To: netdev@vger.kernel.org Cc: Daniel Borkmann , Jakub Zawadzki , Eric Dumazet , linux-kernel@vger.kernel.org Subject: [PATCH net-next v2 2/3] net: add trim helper and convert users Date: Fri, 17 Jan 2014 01:28:38 +0100 Message-Id: <1389918519-23779-3-git-send-email-hannes@stressinduktion.org> X-Mailer: git-send-email 1.8.4.2 In-Reply-To: <1389918519-23779-1-git-send-email-hannes@stressinduktion.org> References: <1389918519-23779-1-git-send-email-hannes@stressinduktion.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Daniel Borkmann As David Laight suggests, we shouldn't necessarily call this reciprocal_divide() when users didn't requested a reciprocal_value(). Lets make the name short and nifty, put this where we have other generic helpers of similar kind and convert users. Joint work with Hannes Frederic Sowa. Cc: Jakub Zawadzki Cc: Eric Dumazet Cc: linux-kernel@vger.kernel.org Signed-off-by: Hannes Frederic Sowa Signed-off-by: Daniel Borkmann --- include/linux/kernel.h | 19 +++++++++++++++++++ include/net/codel.h | 4 +--- net/packet/af_packet.c | 3 +-- 3 files changed, 21 insertions(+), 5 deletions(-) diff --git a/include/linux/kernel.h b/include/linux/kernel.h index ecb8754..62ecbfa 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -193,6 +193,25 @@ extern int _cond_resched(void); (__x < 0) ? -__x : __x; \ }) +/** + * trim - perform a reciprocal multiplication in order to "clamp" a + * value into range [0, ep_ro), where the upper interval + * endpoint is right-open. This is useful, e.g. for accessing + * a index of an array containing ep_ro elements, for example. + * Think of it as sort of modulus, only that the result isn't + * that of modulo. ;) + * More: http://homepage.cs.uiowa.edu/~jones/bcd/divide.html + * + * @val: value to 'trim' + * @ep_ro: right open interval endpoint + * + * Returns a result based on val in interval [0, ep_ro). + */ +static inline u32 trim(u32 val, u32 ep_ro) +{ + return (u32)(((u64) val * ep_ro) >> 32); +} + #if defined(CONFIG_MMU) && \ (defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP)) void might_fault(void); diff --git a/include/net/codel.h b/include/net/codel.h index 3b04ff5..d302b4c 100644 --- a/include/net/codel.h +++ b/include/net/codel.h @@ -46,7 +46,6 @@ #include #include #include -#include /* Controlling Queue Delay (CoDel) algorithm * ========================================= @@ -211,10 +210,9 @@ static codel_time_t codel_control_law(codel_time_t t, codel_time_t interval, u32 rec_inv_sqrt) { - return t + reciprocal_divide(interval, rec_inv_sqrt << REC_INV_SQRT_SHIFT); + return t + trim(interval, rec_inv_sqrt << REC_INV_SQRT_SHIFT); } - static bool codel_should_drop(const struct sk_buff *skb, struct Qdisc *sch, struct codel_vars *vars, diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 91daa01..d327774 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -88,7 +88,6 @@ #include #include #include -#include #ifdef CONFIG_INET #include #endif @@ -1220,7 +1219,7 @@ static unsigned int fanout_demux_hash(struct packet_fanout *f, struct sk_buff *skb, unsigned int num) { - return reciprocal_divide(skb->rxhash, num); + return trim(skb->rxhash, num); } static unsigned int fanout_demux_lb(struct packet_fanout *f, -- 1.8.4.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/