Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751849AbaAQDi2 (ORCPT ); Thu, 16 Jan 2014 22:38:28 -0500 Received: from szxga02-in.huawei.com ([119.145.14.65]:52264 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751695AbaAQDi0 (ORCPT ); Thu, 16 Jan 2014 22:38:26 -0500 Message-ID: <52D8A56F.1010507@huawei.com> Date: Fri, 17 Jan 2014 11:37:19 +0800 From: Weng Meiling User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Thunderbird/24.0.1 MIME-Version: 1.0 To: Will Deacon , Robert Richter CC: "oprofile-list@lists.sf.net" , "linux-kernel@vger.kernel.org" , Li Zefan , "wangnan0@huawei.com" , "zhangwei(Jovi)" , Huang Qiang , "sdu.liu@huawei.com" Subject: Re: [PATCH] oprofile: check whether oprofile perf enabled in op_overflow_handler() References: <52B3F66D.6060707@huawei.com> <20140113084555.GU20315@rric.localhost> <52D4984B.9090600@huawei.com> <20140114150553.GC20315@rric.localhost> <52D5EC44.30101@huawei.com> <20140115102445.GE20315@rric.localhost> <52D73148.4090408@huawei.com> <52D7A750.50906@huawei.com> <20140116115245.GB8360@rric.localhost> <20140116193652.GD22105@mudshark.cambridge.arm.com> In-Reply-To: <20140116193652.GD22105@mudshark.cambridge.arm.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.24.66] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014/1/17 3:36, Will Deacon wrote: > On Thu, Jan 16, 2014 at 11:52:45AM +0000, Robert Richter wrote: >> (cc'ing Will) > > Thanks Robert, > >> The problem of too low sample periods could be solved on ARM by using >> perf's interrupt throttling, you might play around with: >> >> /proc/sys/kernel/perf_event_max_sample_rate:100000 >> >> I am not quite sure whether this works esp. for kernel counters and Try to lower the value of perf_event_max_sample_rate, it works. Testing the following values: 100 500 1000 5000 10000 50000 for the last value, the command start to stall. Just a simple test. :) >> how userland can be notified about throttling. Throttling could be >> worth for operf too, not only for the oprofile kernel driver. >> >> From a quick look it seems there is also code in x86 that dynamically >> adjusts the rate which might be worth being implemented for ARM too. > > Are you referring to the perf_sample_event_took callback? If so, that > certainly looks worth persuing. I'll stick it on my list, thanks! > Thanks Will for doing this. Thanks Weng Meiling > Will > > . > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/