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Date: Tue, 10 Dec 2013 20:57:42 -0800 From: Howard Chu <hyc@...as.com> To: Li Zefan <lizefan@...wei.com> CC: Linux Kernel Mailing List <Linux-Kernel@...r.Kernel.ORG> Subject: Re: sched: RT throttling activated, 3.12.3 Howard Chu wrote: > 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. I just downgraded to 3.10.23 to doublecheck - everything is running normally there, although a few percent slower than I expected. (Last time I tried 3.10 it was 3.10.11.) -- -- Howard Chu CTO, Symas Corp. http://www.symas.com Director, Highland Sun http://highlandsun.com/hyc/ Chief Architect, OpenLDAP http://www.openldap.org/project/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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