The feature is really just that: a way to let users override the clock source. Depending on the clock provided by the end user, it may or may not hurt resolution.
The feature branches are here: https://github.com/compudj/lttng-ust-dev/tree/clock-getcpu-plugin https://github.com/compudj/lttng-tools-dev/tree/clock-plugin-ust Thanks, Mathieu ----- Original Message ----- > Hello > Are there any documents about what the clock override feature is? It seems > that the feature will hurt time resolution,doesn't it? > In fact,I will try to get the symbol addr of __vdso_clock_gettime just like > the same way glibc does with __vdso_gettimeofday. > Is there any other cheaper way to call __vdso_clock_gettime ? > Thanks > zhenyu.ren > > ------------------------------------------------------------------ > > > 发件人：Mathieu Desnoyers <[email protected]> > > > 发送时间：2015年3月27日(星期五) 00:33 > > > 收件人：Jesper Derehag <[email protected]> > > > 抄 送：zhenyu.ren <[email protected]>，lttng-dev > > <[email protected]> > > > 主 题：Re: [lttng-dev] clock_gettime vdso issue > > > Yes, the clock override feature, as well as the getcpu override, > > > should be merged within lttng-ust and lttng-tools master branches > > > this week. Stay tuned! > > > Thanks, > > > Mathieu > > > ----- Original Message ----- > > > > There has been discussions regarding adding capability to override the > > > clock > > > > implementation. > > > > > > > > If that support is arriving, you could always write your own (say a > > > separate > > > > thread reading clock periodically and storing in a cache, then your own > > > > clock implementation could get that cached timestamp). > > > > Obviously you would need to think very carefully about clock resolution > > > and > > > > frequency for your clock thread, but it should from a performance point > > > of > > > > view be big improvement.. > > > > > > > > Maybe Mathieu(?) could shed some light on the clock override? > > > > > > > > /Jesper > > > > > > > > ________________________________ > > > > > Date: Thu, 26 Mar 2015 15:25:49 +0800 > > > > > From: [email protected] > > > > > To: [email protected] > > > > > Subject: [lttng-dev] clock_gettime vdso issue > > > > > > > > > > > > > > > Hi,Team > > > > > > > > > > You may not feel how painful I am with a too old GLIBC which does > > > > > NOT support vdso clock_gettime. Especially in ust case, > > > > > trace_clock_read will call clock_gettime to record the time of every > > > > > event. > > > > > Does anyone know how to avoid system_call clock_gettime with this old > > > > > GLIBC?? > > > > > > > > > > Thanks in advance > > > > > zhenyu.ren > > > > > > > > > > > > > > > _______________________________________________ lttng-dev mailing list > > > > > [email protected] > > > > > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev > > > > > > > > _______________________________________________ > > > > lttng-dev mailing list > > > > [email protected] > > > > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev > > > > > > > -- > > > Mathieu Desnoyers > > > EfficiOS Inc. > > > http://www.efficios.com > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
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