From: Yuyang Du <yuyang.du@intel.com>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Benjamin Segall <bsegall@google.com>,
Paul Turner <pjt@google.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Matt Fleming <matt@codeblueprint.co.uk>,
Mike Galbraith <umgwanakikbuti@gmail.com>
Subject: Re: [PATCH v1 07/10] sched/fair: Remove useless 64-bit to 32-bit variable conversion
Date: Mon, 29 Aug 2016 09:00:59 +0800 [thread overview]
Message-ID: <20160829010059.GG3273@intel.com> (raw)
In-Reply-To: <CAKfTPtD3LUo+aXfWB8DhkWHp+c992hOd4wtYsm2DF+uF1Zwp2w@mail.gmail.com>
On Thu, Aug 25, 2016 at 09:11:56AM +0200, Vincent Guittot wrote:
> On 10 August 2016 at 02:14, Yuyang Du <yuyang.du@intel.com> wrote:
> > In __decay_sum(), the 64-bit to 32-bit variable conversion makes no
> > performance nor correctness use.
>
> Are you sure that there is no impact on 32bits system ?
> Even this will be mainly shift manipulation
>
Honestly, I didn't consider 32-bit system at all, :(
And after all, it's 64-bit shift 32-bit vs. 64-bit shift 64-bit operations.
I'm not an expert, but I intend to believe they are about the same, because
the arithmetic overhead seems to lie in the left part of the shift operation,
both of which are 64-bit (correct me if I'm wrong).
next prev parent reply other threads:[~2016-08-29 8:55 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-10 0:14 [PATCH v1 00/10] Optimize sched avgs computation and implement flat util hierarchy Yuyang Du
2016-08-10 0:14 ` [PATCH v1 01/10] sched/fair: Chance LOAD_AVG_MAX_N from 345 to 347 Yuyang Du
2016-08-24 16:01 ` Vincent Guittot
2016-08-29 0:07 ` Yuyang Du
2016-08-10 0:14 ` [PATCH v1 02/10] documentation: Add scheduler/sched-avg.txt Yuyang Du
2016-08-22 16:48 ` Randy Dunlap
2016-08-10 0:14 ` [PATCH v1 03/10] sched/fair: Add static to remove_entity_load_avg() Yuyang Du
2016-08-10 0:14 ` [PATCH v1 04/10] sched/fair: Rename variable names for sched averages Yuyang Du
2016-08-10 0:14 ` [PATCH v1 05/10] sched/fair: Add __always_inline compiler attribute to __accumulate_sum() Yuyang Du
2016-08-10 0:14 ` [PATCH v1 06/10] sched/fair: Optimize __update_sched_avg() Yuyang Du
2016-08-10 0:14 ` [PATCH v1 07/10] sched/fair: Remove useless 64-bit to 32-bit variable conversion Yuyang Du
2016-08-25 7:11 ` Vincent Guittot
2016-08-29 1:00 ` Yuyang Du [this message]
2016-08-10 0:14 ` [PATCH v1 08/10] sched/fair: Remove scale_load_down() for load_avg Yuyang Du
2016-08-10 0:14 ` [PATCH v1 09/10] sched/fair: Rename scale_load() and scale_load_down() Yuyang Du
2016-08-10 0:14 ` [PATCH v1 10/10] sched/fair: Implement flat hierarchical structure for util_avg Yuyang Du
2016-08-10 0:23 ` [PATCH v1 00/10] Optimize sched avgs computation and implement flat util hierarchy Yuyang Du
2016-08-22 23:26 ` Yuyang Du
2016-08-23 13:28 ` Vincent Guittot
2016-08-23 14:13 ` Peter Zijlstra
2016-08-23 14:45 ` Vincent Guittot
2016-08-23 15:39 ` Dietmar Eggemann
2016-08-29 1:37 ` Yuyang Du
2016-09-01 18:32 ` Dietmar Eggemann
2016-08-24 8:54 ` Morten Rasmussen
2016-08-24 9:48 ` Vincent Guittot
2016-08-29 19:00 ` Yuyang Du
2016-09-01 14:22 ` Morten Rasmussen
2016-08-23 19:09 ` Yuyang Du
2016-08-23 19:01 ` Yuyang Du
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