From: Howard Chu <hyc@symas.com>
To: Li Zefan <lizefan@huawei.com>
Cc: Linux Kernel Mailing List <Linux-Kernel@vger.kernel.org>
Subject: Re: sched: RT throttling activated, 3.12.3
Date: Tue, 10 Dec 2013 19:09:01 -0800 [thread overview]
Message-ID: <52A7D74D.7000804@symas.com> (raw)
In-Reply-To: <52A7D5E5.3070704@huawei.com>
Li Zefan wrote:
> On 2013/12/11 10:59, Howard Chu wrote:
>> I just upgraded a system from a 3.5 kernel to 3.12.3 and attempted to run some new benchmarks on it. I see my test program ramps up in CPU usage for a few seconds and then it gradually tails off. There's nothing obvious in the user code to trigger this behavior, so I check dmesg, and see this:
>>
>> [ 55.037057] JFS: nTxBlock = 8192, nTxLock = 65536
>> [163591.807470] perf samples too long (2758 > 2500), lowering kernel.perf_event_max_sample_rate to 50000
>> [164061.362762] perf samples too long (5204 > 5000), lowering kernel.perf_event_max_sample_rate to 25000
>> [167969.339513] [sched_delayed] sched: RT throttling activated
>> [182741.484637] perf samples too long (294588 > 10000), lowering kernel.perf_event_max_sample_rate to 12500
>> [182741.484726] INFO: NMI handler (perf_event_nmi_handler) took too long to run: 36.665 msecs
>> [182822.633084] perf samples too long (292359 > 20000), lowering kernel.perf_event_max_sample_rate to 6250
>> [182905.606119] perf samples too long (290291 > 40000), lowering kernel.perf_event_max_sample_rate to 3250
>> [199384.293514] perf samples too long (288142 > 76923), lowering kernel.perf_event_max_sample_rate to 1750
>> [208507.301027] perf samples too long (285964 > 142857), lowering kernel.perf_event_max_sample_rate to 1000
>> [208528.976208] perf samples too long (283799 > 250000), lowering kernel.perf_event_max_sample_rate to 500
>>
>> Why is the kernel throttling my server?
>>
>
> Because that is the default setting of the kernel.
Apparently a "new" default that didn't exist in 3.5? The code in question is
not a realtime process. This behavior also wasn't seen in 3.10 or any older
kernels.
> lxc34:/proc/sys/kernel # cat sched_rt_period_us
> 1000000
> lxc34:/proc/sys/kernel # cat sched_rt_runtime_us
> 950000
>
>
--
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/
next prev parent reply other threads:[~2013-12-11 3:09 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-11 2:59 sched: RT throttling activated, 3.12.3 Howard Chu
2013-12-11 3:03 ` Li Zefan
2013-12-11 3:09 ` Howard Chu [this message]
2013-12-11 4:57 ` Howard Chu
2013-12-11 6:06 ` Howard Chu
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