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McKenney" To: lcapitulino@redhat.com, julia@ni.com, bigeasy@linutronix.de Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: rcu: enable rcu_normal_after_boot by default for RT Reply-To: paulmck@linux.ibm.com MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 18110123-0040-0000-0000-0000048B0641 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009968; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000268; SDB=6.01111298; UDB=6.00575895; IPR=6.00891389; MB=3.00023997; MTD=3.00000008; XFM=3.00000015; UTC=2018-11-01 23:02:37 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18110123-0041-0000-0000-000008940724 Message-Id: <20181101230235.GA8757@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-11-01_16:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1811010191 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > The forcing of an expedited grace period is an expensive and very > RT-application unfriendly operation, as it forcibly preempts all running > tasks on CPUs which are preventing the gp from expiring. > > By default, as a policy decision, disable the expediting of grace > periods (after boot) on configurations which enable PREEMPT_RT_FULL. > > Suggested-by: Luiz Capitulino > Signed-off-by: Julia Cartwright > Signed-off-by: Sebastian Andrzej Siewior In case it matters: Acked-by: Paul E. McKenney Alternatively, any reason that I should not pull this into -rcu? Thanx, Paul > diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c > index f56c0fbdf22e..12027723abaf 100644 > --- a/kernel/rcu/update.c > +++ b/kernel/rcu/update.c > @@ -67,7 +67,7 @@ extern int rcu_expedited; /* from sysctl */ > module_param(rcu_expedited, int, 0); > extern int rcu_normal; /* from sysctl */ > module_param(rcu_normal, int, 0); > -static int rcu_normal_after_boot; > +static int rcu_normal_after_boot = IS_ENABLED(CONFIG_PREEMPT_RT_FULL); > module_param(rcu_normal_after_boot, int, 0); > #endif /* #ifndef CONFIG_TINY_RCU */ >