From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B9D49C3A59E for ; Wed, 21 Aug 2019 19:31:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 94AB52064A for ; Wed, 21 Aug 2019 19:31:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730400AbfHUTbZ (ORCPT ); Wed, 21 Aug 2019 15:31:25 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:57352 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730239AbfHUTbL (ORCPT ); Wed, 21 Aug 2019 15:31:11 -0400 Received: from localhost ([127.0.0.1] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1i0WK5-0004Go-IT; Wed, 21 Aug 2019 21:31:09 +0200 Message-Id: <20190821192922.458286860@linutronix.de> User-Agent: quilt/0.65 Date: Wed, 21 Aug 2019 21:09:21 +0200 From: Thomas Gleixner To: LKML Cc: Oleg Nesterov , Ingo Molnar , Peter Zijlstra , John Stultz , Frederic Weisbecker , Anna-Maria Behnsen , Christoph Hellwig Subject: [patch V2 34/38] posix-cpu-timers: Get rid of 64bit divisions References: <20190821190847.665673890@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Instead of dividing A to match the units of B it's more efficient to multiply B to match the units of A. Signed-off-by: Thomas Gleixner --- V2: Fix the dropped update of the expiry cache when the soft limit increased --- kernel/time/posix-cpu-timers.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -798,10 +798,11 @@ static void check_thread_timers(struct t */ soft = task_rlimit(tsk, RLIMIT_RTTIME); if (soft != RLIM_INFINITY) { + /* Task RT timeout is accounted in jiffies. RTTIME is usec */ + unsigned long rtim = tsk->rt.timeout * (USEC_PER_SEC / HZ); unsigned long hard = task_rlimit_max(tsk, RLIMIT_RTTIME); - if (hard != RLIM_INFINITY && - tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) { + if (hard != RLIM_INFINITY && rtim >= hard) { /* * At the hard limit, we just die. * No need to calculate anything else now. @@ -813,7 +814,7 @@ static void check_thread_timers(struct t __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk); return; } - if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) { + if (rtim >= soft) { /* * At the soft limit, send a SIGXCPU every second. */ @@ -910,11 +911,13 @@ static void check_process_timers(struct soft = task_rlimit(tsk, RLIMIT_CPU); if (soft != RLIM_INFINITY) { - u64 softns, ptime = samples[CPUCLOCK_PROF]; + /* RLIMIT_CPU is in seconds. Samples are nanoseconds */ unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU); - unsigned long psecs = div_u64(ptime, NSEC_PER_SEC); + u64 ptime = samples[CPUCLOCK_PROF]; + u64 softns = (u64)soft * NSEC_PER_SEC; + u64 hardns = (u64)hard * NSEC_PER_SEC; - if (hard != RLIM_INFINITY && psecs >= hard) { + if (hard != RLIM_INFINITY && ptime >= hardns) { /* * At the hard limit, we just die. * No need to calculate anything else now. @@ -926,7 +929,7 @@ static void check_process_timers(struct __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk); return; } - if (psecs >= soft) { + if (ptime >= softns) { /* * At the soft limit, send a SIGXCPU every second. */ @@ -936,11 +939,12 @@ static void check_process_timers(struct } __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk); if (soft < hard) { - soft++; - sig->rlim[RLIMIT_CPU].rlim_cur = soft; + sig->rlim[RLIMIT_CPU].rlim_cur = soft + 1; + softns += NSEC_PER_SEC; } } - softns = soft * NSEC_PER_SEC; + + /* Update the expiry cache */ if (softns < pct->bases[CPUCLOCK_PROF].nextevt) pct->bases[CPUCLOCK_PROF].nextevt = softns; }