From: "pang.xunlei" <pang.xunlei@linaro.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: lkml <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@gmail.com>
Subject: Re: [PATCH v2 2/6] sched/rt: Optimize select_task_rq_rt() for non-RT curr task
Date: Tue, 4 Nov 2014 23:09:09 +0800 [thread overview]
Message-ID: <CADcy93Xeb8+pkyjPCazpA5_fhZycrYNf654Ev6j2tEkwqdJXmg@mail.gmail.com> (raw)
In-Reply-To: <20141104094707.79e9ca86@gandalf.local.home>
On 4 November 2014 22:47, Steven Rostedt <rostedt@goodmis.org> wrote:
> On Tue, 4 Nov 2014 22:29:24 +0800
> "pang.xunlei" <pang.xunlei@linaro.org> wrote:
>
>
>> > Migration is not cheap. It causes cache misses and TLB flushes. This is
>> > not something that should be taken lightly.
>> Ok, thanks!
>> But I think the PUSH operation optimized by the former patch is reasonable,
>> since PUSH itselft does involve the Migration. Do I miss something?
>
> For the first patch you may be right, but I want to think about it some
> more. I want to make sure we are not adding any other type of overhead
> with the extra calls.
Yes, this may cause some overhead/latency in idle especially its exit
stage, if that can't be accepted, I think it can also be done just in
find_lowest_rq() after cpupri_find(), we can modify cpupri_find() for
example to return a pri_to_cpu[] index plus one instead of 1, then if
the return index equals CPUPRI_NORMAL+1, then iterate the
"lowest_mask" with something like cpu_idle() judgement to select the
idle cpu.
>
> -- Steve
next prev parent reply other threads:[~2014-11-04 15:09 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-04 11:13 [PATCH v2 1/6] sched/cpupri: Deal with cpupri.pri_to_cpu[CPUPRI_IDLE] for idle cases pang.xunlei
2014-11-04 11:13 ` [PATCH v2 2/6] sched/rt: Optimize select_task_rq_rt() for non-RT curr task pang.xunlei
2014-11-04 12:52 ` Steven Rostedt
2014-11-04 14:29 ` pang.xunlei
2014-11-04 14:47 ` Steven Rostedt
2014-11-04 15:09 ` pang.xunlei [this message]
2014-11-04 11:13 ` [PATCH v2 3/6] sched/cpupri: Remove unnecessary definitions in cpupri.h pang.xunlei
2014-11-04 14:39 ` Steven Rostedt
2014-11-04 11:13 ` [PATCH v2 4/6] sched/dl: Modify cpudl_find() for more cases of electing best_cpu pang.xunlei
2014-11-04 11:13 ` [PATCH v2 5/6] sched/dl: Optimize select_task_rq_dl() for non-DL curr task pang.xunlei
2014-11-04 11:24 ` Wanpeng Li
2014-11-04 14:19 ` pang.xunlei
2014-11-04 23:30 ` Wanpeng Li
2014-11-04 14:45 ` Steven Rostedt
2014-11-04 15:11 ` Peter Zijlstra
2014-11-04 23:33 ` Wanpeng Li
2014-11-04 11:13 ` [PATCH v2 6/6] sched/dl: Remove unnecessary definitions in cpudeadline.h pang.xunlei
2014-11-04 12:21 [PATCH v2 2/6] sched/rt: Optimize select_task_rq_rt() for non-RT curr task Hillf Danton
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