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Date: Fri, 23 Oct 2015 14:52:11 +0200 From: Peter Zijlstra <peterz@...radead.org> To: "Wangnan (F)" <wangnan0@...wei.com> Cc: Alexei Starovoitov <ast@...mgrid.com>, pi3orama <pi3orama@....com>, xiakaixu <xiakaixu@...wei.com>, davem@...emloft.net, acme@...nel.org, mingo@...hat.com, masami.hiramatsu.pt@...achi.com, jolsa@...nel.org, daniel@...earbox.net, linux-kernel@...r.kernel.org, hekuang@...wei.com, netdev@...r.kernel.org Subject: Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling On Thu, Oct 22, 2015 at 06:28:22PM +0800, Wangnan (F) wrote: > information to analysis when glitch happen. Another way we are trying to > implement > now is to dynamically turn events on and off, or at least enable/disable > sampling dynamically because the overhead of copying those samples > is a big part of perf's total overhead. After that we can trace as many > event as possible, but only fetch data from them when we detect a glitch. So why don't you 'fix' the flight recorder mode and just leave the data in memory and not bother copying it out until a glitch happens? Something like this: lkml.kernel.org/r/20130708121557.GA17211@...ns.programming.kicks-ass.net it appears we never quite finished that. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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