From: Alex Shi <alex.shi@intel.com>
To: Michael Wang <wangyun@linux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>, Paul Turner <pjt@google.com>,
Mike Galbraith <efault@gmx.de>,
Andrew Morton <akpm@linux-foundation.org>,
Ram Pai <linuxram@us.ibm.com>,
"Nikunj A. Dadhania" <nikunj@linux.vnet.ibm.com>,
Namhyung Kim <namhyung@kernel.org>
Subject: Re: [RFC PATCH v3 1/3] sched: schedule balance map foundation
Date: Fri, 22 Feb 2013 12:46:54 +0800 [thread overview]
Message-ID: <5126F83E.9060206@intel.com> (raw)
In-Reply-To: <5126F1D4.5030308@linux.vnet.ibm.com>
On 02/22/2013 12:19 PM, Michael Wang wrote:
>
>> > Why not seek other way to change O(n^2) to O(n)?
>> >
>> > Access 2G memory is unbelievable performance cost.
> Not access 2G memory, but (2G / 16K) memory, the sbm size is O(N).
>
> And please notice that on 16k cpus system, topology will be deep if NUMA
> enabled (O(log N) as Peter said), and that's really a good stage for
> this idea to perform on, we could save lot's of recursed 'for' cycles.
>
CPU execute part is very very fast compare to the memory access, the
'for' cycles cost is most on the memory access for many domain/groups
data, not instruction execution.
In a hot patch, several KB memory access will cause clear cpu cache
pollution then make kernel slowly.
--
Thanks Alex
next prev parent reply other threads:[~2013-02-22 4:46 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-29 9:08 [RFC PATCH v3 0/3] sched: simplify the select_task_rq_fair() Michael Wang
2013-01-29 9:09 ` [RFC PATCH v3 1/3] sched: schedule balance map foundation Michael Wang
2013-02-20 13:21 ` Peter Zijlstra
2013-02-21 4:52 ` Michael Wang
2013-02-20 13:25 ` Peter Zijlstra
2013-02-21 4:58 ` Michael Wang
2013-02-21 11:37 ` Peter Zijlstra
2013-02-22 2:53 ` Michael Wang
2013-02-22 3:33 ` Alex Shi
2013-02-22 4:19 ` Michael Wang
2013-02-22 4:46 ` Alex Shi [this message]
2013-02-22 5:05 ` Michael Wang
2013-01-29 9:09 ` [RFC PATCH v3 2/3] sched: build schedule balance map Michael Wang
2013-01-29 9:10 ` [RFC PATCH v3 3/3] sched: simplify select_task_rq_fair() with " Michael Wang
2013-02-18 5:52 ` [RFC PATCH v3 0/3] sched: simplify the select_task_rq_fair() Michael Wang
2013-02-20 10:49 ` Ingo Molnar
2013-02-20 13:32 ` Peter Zijlstra
2013-02-20 14:05 ` Mike Galbraith
2013-02-21 5:21 ` Michael Wang
2013-02-21 5:14 ` Michael Wang
2013-02-21 4:51 ` Michael Wang
2013-02-21 6:11 ` Mike Galbraith
2013-02-21 7:00 ` Michael Wang
2013-02-21 8:10 ` Mike Galbraith
2013-02-21 9:08 ` Michael Wang
2013-02-21 9:43 ` Mike Galbraith
2013-02-22 2:36 ` Michael Wang
2013-02-22 5:02 ` Mike Galbraith
2013-02-22 5:26 ` Michael Wang
2013-02-22 6:13 ` Mike Galbraith
2013-02-22 6:42 ` Michael Wang
2013-02-22 8:17 ` Mike Galbraith
2013-02-22 8:35 ` Michael Wang
2013-02-22 8:21 ` Peter Zijlstra
2013-02-22 9:10 ` Michael Wang
2013-02-22 9:39 ` Peter Zijlstra
2013-02-22 9:58 ` Michael Wang
2013-02-21 9:20 ` Michael Wang
2013-02-21 10:20 ` Peter Zijlstra
2013-02-22 2:37 ` Michael Wang
2013-02-22 5:08 ` Mike Galbraith
2013-02-22 6:06 ` Michael Wang
2013-02-22 6:19 ` Mike Galbraith
2013-02-22 8:36 ` Peter Zijlstra
2013-02-22 9:11 ` Michael Wang
2013-02-22 9:57 ` Peter Zijlstra
2013-02-22 10:08 ` Michael Wang
2013-02-22 9:40 ` Mike Galbraith
2013-02-22 9:54 ` Ingo Molnar
2013-02-22 10:01 ` Mike Galbraith
2013-02-22 12:11 ` Ingo Molnar
2013-02-22 12:35 ` Mike Galbraith
2013-02-22 13:06 ` Ingo Molnar
2013-02-22 14:30 ` Mike Galbraith
2013-02-22 14:42 ` Mike Galbraith
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