From: Balbir Singh <balbir@linux.vnet.ibm.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
"Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
Dhaval Giani <dhaval@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org, "Zhang,
Yanmin" <yanmin_zhang@linux.intel.com>
Subject: Re: Make yield_task_fair more efficient
Date: Thu, 21 Feb 2008 15:01:43 +0530 [thread overview]
Message-ID: <47BD44FF.7070104@linux.vnet.ibm.com> (raw)
In-Reply-To: <20080221090430.GA20055@elte.hu>
Ingo Molnar wrote:
> * Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
>
>> If you insist that sched_yield() is bad, I might agree, but how does
>> my patch make things worse. [...]
>
> it puts new instructions into the hotpath.
>
>> [...] In my benchmarks, it has helped the sched_yield case, why is
>> that bad? [...]
>
> I had the same cache for the rightmost task in earlier CFS (it's a
> really obvious thing) but removed it. It wasnt a bad idea, but it hurt
> the fastpath hence i removed it. Algorithms and implementations are a
> constant balancing act.
This is more convincing, was the code ever in git? How did you measure the
overhead? What are your plans for reports with regressions where
kernel.compat_sched_yield is set to 1?
I have an alternate approach in mind (that I need to find time for),
threaded-rbtrees. Walking the tree is really efficient, specially finding
successor of a node.
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
next prev parent reply other threads:[~2008-02-21 9:37 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-02-21 5:33 Make yield_task_fair more efficient Balbir Singh
2008-02-21 6:04 ` Ingo Molnar
2008-02-21 6:51 ` Balbir Singh
2008-02-21 7:07 ` Ingo Molnar
2008-02-21 7:39 ` Balbir Singh
2008-02-21 8:43 ` Peter Zijlstra
2008-02-21 8:50 ` Balbir Singh
2008-02-21 9:04 ` Ingo Molnar
2008-02-21 9:31 ` Balbir Singh [this message]
2008-02-21 9:42 ` Ingo Molnar
2008-02-21 9:44 ` Balbir Singh
2008-02-21 9:43 ` Peter Zijlstra
2008-02-21 9:42 ` Balbir Singh
2008-02-21 10:01 ` Peter Zijlstra
2008-02-21 10:07 ` Balbir Singh
2008-02-21 11:12 ` Peter Zijlstra
2008-02-21 11:27 ` Balbir Singh
2008-02-21 20:38 ` Jens Axboe
2008-02-21 20:55 ` Jens Axboe
2008-02-22 3:27 ` Balbir Singh
2008-02-21 10:17 ` Balbir Singh
2008-02-21 12:02 ` Mike Galbraith
2008-02-21 12:06 ` Mike Galbraith
2008-02-21 13:29 ` Balbir Singh
2008-02-21 14:38 ` Jörn Engel
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