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Mon, 19 Nov 2018 17:31:39 +0000 Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userv0022.oracle.com (8.14.4/8.14.4) with ESMTP id wAJHVcJ2022071 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 19 Nov 2018 17:31:39 GMT Received: from abhmp0006.oracle.com (abhmp0006.oracle.com [141.146.116.12]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id wAJHVbpC032483; Mon, 19 Nov 2018 17:31:37 GMT Received: from [10.152.35.100] (/10.152.35.100) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 19 Nov 2018 09:31:37 -0800 Subject: Re: [PATCH v3 05/10] sched/fair: Hoist idle_stamp up from idle_balance To: Valentin Schneider , mingo@redhat.com, peterz@infradead.org Cc: subhra.mazumdar@oracle.com, dhaval.giani@oracle.com, daniel.m.jordan@oracle.com, pavel.tatashin@microsoft.com, matt@codeblueprint.co.uk, umgwanakikbuti@gmail.com, riel@redhat.com, jbacik@fb.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, quentin.perret@arm.com, linux-kernel@vger.kernel.org References: <1541767840-93588-1-git-send-email-steven.sistare@oracle.com> <1541767840-93588-6-git-send-email-steven.sistare@oracle.com> <9ad62a6f-0269-a5d9-9757-ba5419f9cc1d@arm.com> From: Steven Sistare Organization: Oracle Corporation Message-ID: <0d8ceaff-6368-2dff-9e2c-e5928ab39bab@oracle.com> Date: Mon, 19 Nov 2018 12:31:34 -0500 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.1 MIME-Version: 1.0 In-Reply-To: <9ad62a6f-0269-a5d9-9757-ba5419f9cc1d@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9082 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1811190160 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/9/2018 2:07 PM, Valentin Schneider wrote: > Hi Steve, > > On 09/11/2018 12:50, Steve Sistare wrote: >> Move the update of idle_stamp from idle_balance to the call site in >> pick_next_task_fair, to prepare for a future patch that adds work to >> pick_next_task_fair which must be included in the idle_stamp interval. >> No functional change. >> >> Signed-off-by: Steve Sistare >> --- >> kernel/sched/fair.c | 23 ++++++++++++++--------- >> 1 file changed, 14 insertions(+), 9 deletions(-) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 9031d39..da368ed 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -3725,6 +3725,8 @@ static inline void update_misfit_status(struct task_struct *p, struct rq *rq) >> rq->misfit_task_load = task_h_load(p); >> } >> >> +#define IF_SMP(statement) statement >> + > > I'm not too hot on those IF_SMP() macros. Since you're not introducing > any other user for them, what about an inline function for rq->idle_stamp > setting ? When it's mapped to an empty statement (!CONFIG_SMP) GCC is > smart enough to remove the rq_clock() that would be passed to it on > CONFIG_SMP: That may be true now, but I worry that rq_clock or its subroutines may gain side effects in the future that prevent the compiler from removing it. However, I could push rq_clock into the inline function: static inline void rq_idle_stamp_set(rq) { rq->idle_stamp = rq_clock(rq); } static inline void rq_idle_stamp_clear(rq) { rq->idle_stamp = 0; } I like that better, do you? - Steve > ----->8----- > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index c11adf3..34d9864 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -3725,7 +3725,10 @@ static inline void update_misfit_status(struct task_struct *p, struct rq *rq) > rq->misfit_task_load = task_h_load(p); > } > > -#define IF_SMP(statement) statement > +static inline void set_rq_idle_stamp(struct rq *rq, u64 value) > +{ > + rq->idle_stamp = value; > +} > > static void overload_clear(struct rq *rq) > { > @@ -3772,7 +3775,7 @@ static inline int idle_balance(struct rq *rq, struct rq_flags *rf) > return 0; > } > > -#define IF_SMP(statement) /* empty */ > +static inline void set_rq_idle_stamp(struct rq *rq, u64 value) {} > > static inline void overload_clear(struct rq *rq) {} > static inline void overload_set(struct rq *rq) {} > @@ -6773,12 +6776,12 @@ done: __maybe_unused; > * We must set idle_stamp _before_ calling idle_balance(), such that we > * measure the duration of idle_balance() as idle time. > */ > - IF_SMP(rq->idle_stamp = rq_clock(rq);) > + set_rq_idle_stamp(rq, rq_clock(rq)); > > new_tasks = idle_balance(rq, rf); > > if (new_tasks) > - IF_SMP(rq->idle_stamp = 0;) > + set_rq_idle_stamp(rq, 0); > > /* > * Because idle_balance() releases (and re-acquires) rq->lock, it is >